Adsorption of Dyes by Chitosan-Selenium Nanoparticles: Recent Developments and Adsorption Mechanisms

Most of the dyes are a dangerous class of water contaminants that have affected the environment drastically. Nano-sized compositeis the best decision cutting edge adsorbent for the evacuation of water poisons as such materials are related to the attributes of straightforwardness, adaptability, adequacy, and high surface reactivity. In this investigation, we have synthesized a nanostructured Chitosan-Selenium nanoparticle by green synthesis method using Justicia adhatoda plant leaves extract. Synthesis and characterization of Chitosan-Selenium nanoparticle were described by UVvisible spectroscopy, FTIR spectrum examinations, Particle Size Analysis, and XRD Spectrum analysis. From the outcomes, it was inferred that the Chitosan-Selenium nanoparticle was additionally utilized as an adsorbent for the expulsion of Rhodamine dye from the aqueous solution. Langmuir isotherm model was effectively usedfor the adsorption study of Chitosan-Selenium nanoparticle adsorbent. For the adsorption studies, parameters such asdosages, pH, and temperature were studied. The adsorption process was remarkably fast and reached equilibrium within 24hrs. The isotherm information was steady with the Langmuir model, and the most extreme adsorption limits of the Chitosan-Selenium nanoparticle adsorbent was 34.5mg.g for Rhodamine dye. Accordingly, nanoparticleswill be the only wayfor the future planned water treatment process.


INTRODUCTION
Industrial, agricultural and domestic wastes, due to the rapid development in technology, are discharged in several environments. Generally, this discharge is directed to the nearest water sources such as rivers, lakes, and seas. The textile dyeing process is an important source of contamination responsible for the continuous pollution of the environment. Textile, paper, painting, and coating industries are majorsources of dye pollutants. A large amount of dye wastewateris emptied into freshwater bodies which have negativeconsequences on the environment and human health (Oliveiraet al. 2008). Wastewater from dye-stuff and textile industries have dye concentrations below 1 g/ dm 3 , high alkalinity, Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), and total dissolved solids (Kaushik & Malik 2009). The reactive, directive, and acid dye widely used in silk, cotton, and wool processing as dyes (El-Sharkawy et al. 2007). Dye wastewater that ends up in freshwater bodies causes havoc to aquatic species by increasing toxicity in COD. It also affects the photosynthetic activities of aquatic plants through the reduction of light penetration (Oliveira et al. 2008). It has been reported that high COD,BOD values, particulate matter (PM) and sediments, grease, and oil in effluents lead to the depletion of dissolved oxygen creating serious consequences on aquatic species (Wang et al. 2011, Hamza & Hamoda 1980, Shaul et al. 1982, Shelley et al. 1980. The methods of colour removal from industrial effluents include biological treatment, coagulation, flotation, adsorption, oxidation, and hyperfiltration. Among the treatment options, adsorption has become one of the most effective and comparable lowcost methods for the decolourization of textile wastewater. Different adsorbents have been used for the removal from aqueous solutions of various materials, such as dyes, metal ions, and other organic materials include perlite (Dogan et al. 2000, Demirbas & Dogan 2002 bentonite (Bereket et al. 1997), silica gels (Mohamed et al. 1996), fly ash (Mohan et al. 2002, Gupta et al. 2000, lignite (Allen et al. 1989), peat (Ho& Mckay 1998), silica (Mckay et al. 1981). However, all these processes are costly and cannot be used by small industries to treat a wide range of dye wastewater (Dogan et al. 2000). The adsorption process provides an attractive alternative for the treatment of contaminated waters, especially if the sorbent is inexpensive and does not require an additional pretreatment step before its application (Mckay et al. 1981, Ho & Mckay All the chemicals were purchased from Himedia Private Ltd, Mumbai. The plant Justicia adhatoda leaves were collected from Sri Paramakalyani Centre of Excellence in Environmental Sciences, Manonmaniam Sundaranar University, Alwarkurichi.

Preparation of Adathoda Leaf Extract
Fresh and young leaves (5g) of the Adathoda plant were washed thoroughly with distilled water and cut into fine pieces. Leaves were subsequently macerated in 20 mL of Tris-HCl (pH7.5) with the help of mortar and pestle. A thick slurry of leaf thus recovered was subjected to centrifugation at 10,000 rpm for 5 min at 4°C. The supernatant was transferred into fresh sterile centrifuge tubes followed by its preservation in refrigerated conditions. The aqueous extract of leaf obtained in this manner was used as a precursor for the synthesis of selenium nanoparticles.

Synthesis of Selenium Nanoparticle
In a typical synthesis of selenium nanoparticles, the leaf extract (2 mL) which contains dissolved phytochemicals was added dropwise into 20 mL of sodium selenite solution (10mM). The addition of the leaf extract was carried out under magnetic stirring. The content was later on placed on to a rotator orbital shaker operating at 200rpm for 24 h. The incubation of the mixture was performed at 30°C in dark conditions. The reduction of selenium ions was monitored by sampling an aliquot (3 mL) of the mixture at intervals of 12 h, followed by measurement of the UV-Vis spectrophotometer. To find out the absorption maximum, a spectral scanning analysis was carried out by measuring the optical density of the content from wavelength 250 to 750 nm.

Synthesis of Chitosan-Selenium Nanoparticle (CS-Se NPs)
Stock solutions of sodium selenite (20mmol/L) and ascorbic acid solution (80mmol/L) were prepared with double-distilled water at room temperature. 1 gm of chitosan (CS, 1% w/w) was dispersed in 4% (w/w) acetic acid at room temperature and stirred for complete dissolution. For the preparation of the CS-Se NPs solution, 1mL (10 mM) of sodium selenite solution, ascorbic acid, and chitosan solution were mixed and the solution was subjected to vigorous mixing. Then, the reaction mixture was diluted to 10 mL with distilled water. The sample was filtered and dried in the hot air oven at 150°C for using adsorption studies.

Batch Equilibrium Studies
Batch adsorption experiments were carried out by agitating 1g of the Chitosan-Selenium nanoparticle with the effect of initial Rhodamine dye concentrations was carried out by shaking 100 mLRhodamine dye solutions of desired concentrations (20 to 100 mg/L) with 1g of the adsorbent at different dosages (1.0, 2.0 and 3.0g/L) pH (5.8, 6.8 and 9.4) and temperature (30°C, 45°C, and 60°C) using an orbital shaker operating at 200 rpm. Before the measurement of colour, the dye solutions were filtered through Whatman No. 1 filter paper to exclude the adsorbent particles. Dye concentrations were measured at the wavelengths corresponding to their maximum absorbance using a spectrophotometer. The effect of pH was studied by adjusting the pH of dye solutions using 1 N H 2 SO 4 or 1 N NaOH solution pH was measured using a pH meter. The samples were withdrawn from the shaker at a pre-determined time of 24hrs. The residual concentrations of Rhodamine dye were measured using UV spectrophotometer equipment (Shimadzu UV/Vis 1601 Spectrophotometer, Japan). The maximum wavelength of this dye is  max 555 nm.

Mass Balance Equation
Throughout the experiment the mass balance equation was used, to find the amount of protein adsorbed in each flask which was determined by the equation, Where, Q -Adsorption capacity (mg/g) So using this equation the amount of dye being adsorbed by the adsorbent was determined.

RESULTS AND DISCUSSION
The synthesis of selenium nanoparticles was preliminarily analysed by the colour change of the reaction mixture. The reaction mixture contains sodium selenite solution, ascorbic acid, and plant extract. The plant extract was used as a reducing agent forthe synthesis of nanoparticles. Ascorbic acid was used as an initiator of the reduction reaction. All the solutions were mixed and colour change was occurring from colourless sodium selenite solution to ruby red colour. A similar result was observed by Kirupagaran et al.(2016), synthesized selenium nanoparticles using an extract of Leucas lavandulifolia and Fenugreek seed extract (Ramamurthy et al. 2013). Visual observation of the chitosan stabilized selenium nanoparticles solution showed a colour change from light yellow to brick red indicating the formation of red-coloured elemental Se resulting in the selenium nanoparticle formation (Bajaj et al. 2012). This red colour due to the excitation of surface plasmon vibrations of selenium nanoparticles provides a convenient spectroscopic signature of their production whereas no colour change could be demonstrated in a solution of selenium selenite as a negative control. Many related studies revealed that metal reduction and precipitation might involve a complex of either reductase, capping proteins, quinones or cytochromes, electron shuttles, or phytochelatins that are known to reduce and stabilize various metal, metal oxides and metal sulphide nanoparticles (Bajaj et al. 2012).

UV-Vis Spectrophotometer
Reduction of selenium ions into selenium nanoparticles during exposure to plant extracts and ascorbic acid was observed using UV-Vis spectra. The metal nanoparticles have free electrons, which give the SPR absorption band, due to the combined vibration of electrons of metal nanoparticles. Chitosan stabilized selenium nanoparticles shown the SPR band at 450 and 310 nm indicates the formation of selenium nanoparticles. Some of the minor peaks were also observed due to the presence of biomolecules from chitosan Fig.1. Previous studies have shown that the spherical Se-NPs contribute to the absorption bands at around 250-400nm in the UV-Visible spectra (Fesharaki et al. 2010) reported  max at 280 nm (Lin et al. 2005) at 355 nm (Shen et al. 2000) at 380 nm. The UV data may support further characterization of Adhatoda leaf extract and chitosan mediated selenium nanoparticles. Chitosan stabilized selenium nanoparticles were purified by membrane dialysis process. Dialysed nanoparticles were dried in a hot air oven at 60°C for 4 h. The powder form of the selenium nanoparticles was used for further analysis.

FT-IR Analysis
The functional groups present in green synthesized chitosan-selenium nanoparticles were identified by FTIR spectra. FTIR analysed at different wavenumber range from 4000 to 500cm -1 . The functional groups involved in the synthesis of selenium nanoparticles using chitosan were detected with the help of FT-IR analysis (Fig. 2). Broadband at 3226cm -1 was observed due to the presence of O-H stretching carboxylic acids. A very small band at 2878 cm -1 was formed corresponds to C-H stretch alkanes. A strong narrowband was positioned at N-H bend primary amines. A small band at 1297 cm -1 indicates the presence of N-O symmetric stretching Nitro compounds and C-N stretching aromatic amines. A narrow band was formed at 1023 due to C-N

FT-IR Analysis
The functional groups present in green synthesized chitosan-selenium nan identified by FTIR spectra. FTIR analysed at different wavenumber range from 4 The functional groups involved in the synthesis of selenium nanoparticles usin detected with the help of FT-IR analysis (Fig. 2). Broadband at 3226cm -1 was obs presence of O-H stretching carboxylic acids. A very small band at 2878 cm corresponds to C-H stretch alkanes. A strong narrowband was positioned at Namines. A small band at 1297 cm -1 indicates the presence of N-O symmetric compounds and C-N stretching aromatic amines. A narrow band was formed at 1 stretch aliphatic amines. Therefore, the FT-IR results imply that the ch nanoparticles were successfully synthesized and capped with bio-compounds pres aqueous extract and chitosan by using a green method. Fig.2: FTIR spectrum of chitosan-selenium nanoparticles. stretch aliphatic amines. Therefore, the FT-IR results imply that the chitosan-selenium nanoparticles were successfully synthesized and capped with bio-compounds present in the leaf aqueous extract and chitosan by using a green method.

X-ray Diffraction
The crystal structure and the phase composition of chitosan-selenium nanoparticles were determined, using XRD techniques shown in Fig. 3. The XRD pattern suggests that the sample is nanocrystalline and matches very well with that of the standard selenium powder confirming the formation of selenium particles using leaf extract.  (Shen et al. 2000). Chitosan coupled selenium nanoparticles not shown specific crystalline planes and definite shapes indicate that synthesized nanocomposite is a polydispersed amorphous structure. Fig. 4. shows the number of frequency histograms of particle size data on a linear scale. The smooth curve drawn through the histogram is a valid size-frequency curve insufficient particlesare counted and the size interval is at least ten (Kirupagaran et al. 2016). As it is observed in Fig. 4 the average size distribution of the chitosan-selenium nanoparticle is 87-152 nm.

Adsorption Isotherm of Rhodamine Dye
The equilibrium adsorption isotherm is of fundamental importance in the design of adsorption systems. The isotherm expresses the relation between the mass of dye adsorbed at a particular temperature and dosages and the liquid phase of dye concentration. For any adsorption investigation one of the most important parameters required to understand the behaviour of the adsorption process in the adsorption isotherm (Jain et al. 2003, Jumasiah et al. 2005, Kadirvelu et al. 2005, Kamel et al. 2009). The shape of an isotherm not only provides information about the affinity of the dye molecule for adsorption but also reflects the possible mode of adsorbing dye molecule. The most common way of obtaining an adsorption isotherm is to determine the concentration of dye solution before and after the adsorption experiments, although several attempts have been made to find the adsorbed amount.

Effect of Dosages
The effect of adsorbent dosages on Rhodamine dye uptakes for three different dosages (Chitosan-Selenium Nanoparticle) (1.0, 2.0, and 3.0 g/L) is shown in Fig. 5. It can be observed that as the dosages were increased, the adsorption of dye increases. The results show that there is a gradual increase in adsorption with increasing dosages. Such an effect of probably due to the inability of the large dye molecule to penetrate all the internal pore structure Chitosan-Selenium nanocomposite and a similar phenomenon was reported previously for the adsorption of certain dyes on various adsorbents (Mckay 1984. Feng et al. 2001. Ferrero 2000. The results revealed that the dye uptake increased with increasing dosages at1.0 g/L 16.14 mg/g. 2.0g/L, 24.36.0 mg/g and 3.0g/L, 33.90 mg/g). This is due to the larger surface area made available for adsorption. It was also observed that the increase in dosages, increases the dye lysis number of frequency histograms of particle size data on a linear scale. The n through the histogram is a valid size-frequency curve insufficient particlesare ize interval is at least ten (Kirupagaran et al. 2016). As it is observed in Fig. 4 istribution of the chitosan-selenium nanoparticle is 87-152 nm.

erm of Rhodamine Dye
dsorption isotherm is of fundamental importance in the design of adsorption therm expresses the relation between the mass of dye adsorbed at a particular counted and the size interval is at least ten (Kirupagaran et al. 2016). As it is o the average size distribution of the chitosan-selenium nanoparticle is 87-152 nm

Adsorption Isotherm of Rhodamine Dye
The equilibrium adsorption isotherm is of fundamental importance in the desi systems. The isotherm expresses the relation between the mass of dye adsorbe uptake. It is obvious that the smaller particles, which have higher solid-liquid interfacial areas, will have higher adsorption rates.Thus dye uptake was maximum at a higher adsorbent dosage. This could be attributed to the fact that as the adsorbent dosage is increased, more adsorption sites are available for dye, thus enhancing the uptake. Also, with increasing adsorbent load, the quantity of dye adsorbed onto the unit weight of the adsorbent gets reduced, thus causing a decrease in q e value with increasing Chitosan-Selenium nanoparticle loading (Rathinam et al. 2007).

Effect of Temperature
Temperature is an important parameter for the adsorption process. A plot of the Rhodamine dye uptake as a function of temperature (30, 45, and 600°C) is shown in Fig. 6. The results revealed that the dye uptake increased with increasing temperature at 30°C, 16.14 mg/g, 45°C, 24.36.0 mg/g, and 60°C, 25.60 mg/g). The adsorption of dye at higher temperatures was found to be greater compared to that at a lower temperature. The curves indicate the strong tendency of the process for monolayer formation (Sivaraj et al. 2001, Annadurai et al. 2002, Yu et al. 2002, Ravi Kumar 2000,Muzzarelli 1973). The increase in temperature would increase the mobility of the large dye ion and also produces a swelling effect within the internal structure of the Chitosan-Selenium nanoparticle, thus enabling the large dye molecule to penetrate further (Muzzarelli 1973, Faria et al. 2004). Therefore, the adsorption capacity should largely depend on the chemical interaction between the functional groups on the adsorbent surface and the adsorbate and should increase with temperature rising (Rinaudo 2006,Knorr et al.1985, Kawamura et al.1997). This effect is characteristic of a chemical reaction or bond being involved in the adsorption process. The increase in adsorption with temperature could be due to changes in pore size, an increase in kinetic energy of dye molecule, and enhanced rate of diffusion of sorbate (Aksu 2002, Rathinam et al. 2007). Fig. 7.showsthe effect of pH on adsorption of the Rhodamine dye onto Chitosan-Selenium nanoparticle. In general, uptakes were much higher in acidic solutions than those in neutral and alkaline conditions. The maximum values of the adsorption capacity ratio between acidic and alkaline conditions reached 12.14 to 19.49 mg/g, respectively. At lower pH more protons will be available to protonate amino groups of chitosan molecules to form groups -NH 3+ , thereby increasing the electrostatic attractions between negatively charged dye anions and positively charged adsorption sites and causing an increase in dye adsorption (Gardiner & Brune 1978, Ganesh et al. 1994, Fu & Viraraghavan 2001, Forgacs et al. 2004). This explanation agrees with our data on the pH effect. It can be seen that the pH of aqueous solution plays an important role in the adsorption of Rhodamine dye onto Chitosan-Selenium nanoparticle. The results showed a direct influence of the pH of the solution on the heterogeneous adsorption process. In alkaline solutions, adsorption efficiency was more than that in acidic solutions. It is because the decomposition of Chitosan-Selenium nanoparticle takes place in acidic and neutral solutions (Daneshvar et al. 2007).

Langmuir Isotherm
The Langmuir isotherm (1916Langmuir isotherm ( , 1918 has found successful application to many other real sorption processes and it can be used to explain the sorption of Rhodamine dye into ecific dye uptake at different dosages (Chitosan-Selenium nanoparticle) with oncentration.
ature important parameter for the adsorption process. A plot of the Rhodamine dye on of temperature (30, 45, and 600°C) is shown in Fig. 6. The results revealed ke increased with increasing temperature at 30°C, 16.14 mg/g, 45°C, 24.36.0 5.60 mg/g). The adsorption of dye at higher temperatures was found to be greater at a lower temperature. The curves indicate the strong tendency of the process mation (Sivaraj et al. 2001, Annadurai et al. 2002, Yu et al. 2002. The increase in temperature would increase the mobility of the large dye uces a swelling effect within the internal structure of the Chitosan-Selenium enabling the large dye molecule to penetrate further (Muzzarelli 1973, Faria et ore, the adsorption capacity should largely depend on the chemical interaction ional groups on the adsorbent surface and the adsorbate and should increase with g (Rinaudo 2006,Knorr et al.1985, Kawamura et al.1997). This effect is chemical reaction or bond being involved in the adsorption process. The increase temperature could be due to changes in pore size, an increase in kinetic energy and enhanced rate of diffusion of sorbate (Aksu 2002, Rathinam et al. 2007).  nanoparticle. In general, uptakes were much higher in acidic solutions than alkaline conditions. The maximum values of the adsorption capacity ratio alkaline conditions reached 12.14 to 19.49 mg/g, respectively. At lower pH available to protonate amino groups of chitosan molecules to form gro increasing the electrostatic attractions between negatively charged dye a charged adsorption sites and causing an increase in dye adsorption (Gard Ganesh et al. 1994, Fu & Viraraghavan 2001, Forgacs et al. 2004). This exp our data on the pH effect. It can be seen that the pH of aqueous solution play the adsorption of Rhodamine dye onto Chitosan-Selenium nanoparticle. T direct influence of the pH of the solution on the heterogeneous adsorption solutions, adsorption efficiency was more than that in acidic solutions decomposition of Chitosan-Selenium nanoparticle takes place in acidic a (Daneshvar et al. 2007). Chitosan-Selenium nanoparticle. A basic assumption of the Langmuir theory is that sorption takes place at specific sites within the adsorbent (Kawamura et al. 1993, Lee& Low 1987, Wei et al.1992. The data obtained from the adsorption experiment conducted in the present investigation were fitted in different Rhodamine dye concentrations, dosages, pH, and temperature in the isotherm equation. The saturation monolayer can be represented by the expression (2).
specific dye uptake at different pH (Chitosan-Selenium nanoparticle) with concentration.
erm otherm (1916, 1918) has found successful application to many other real sorption can be used to explain the sorption of Rhodamine dye into Chitosan-Selenium basic assumption of the Langmuir theory is that sorption takes place at specific adsorbent (Kawamura et al. 1993, Lee& Low 1987, Wei et al.1992. The data e adsorption experiment conducted in the present investigation were fitted in ine dye concentrations, dosages, pH, and temperature in the isotherm equation. .

Linear Regression of Langmuir Isotherm -Chitosan-Selenium Nanocomposite-Rhodamine Dye
A plot of Langmuir isotherm Type -I -IV (C e /q e Vs C e -Type-I. 1/qe vs 1/C e -Type -II. q e Vs qe/C e -Type-III. q e /C e Vs q e -Type-IV) (Table1)resulted in a linear graphical relation indicating the applicability of the above model (Different dosage 1.0, 2.0, and 3.0g/L, pH: 5.8, 6.8, and 9.4. Temperature: 30°C, 45°C, and 60°C) as shown in Figs.8-19. The values are calculated from the slope and intercept of different straight lines representing the different dosages, pH, and temperature (q m ) adsorption capacity. The Langmuir isotherm constant (K L ) in Eqn (3 -7) is a measure of the amount of dye adsorbed when the monolayer is completed.
Monolayer capacity (q m ) of the adsorbent for the dye is comparably obtained from adsorption isotherm. The observed statistically significant (at the 95% confidence level) linear relationship as evidence of these by the R 2 values (close to unity) indicate the applicability of the isotherm (Langmuir isotherm) and surface.
The Langmuir isotherm constants along with correction coefficients are reported in Tables2-5.It is also clear from the shape of the adsorption isotherm, that it belongs to the L 2 category of isotherm, which indicates the normal (or) Langmuir type of adsorption (Chiou et al. 2003, Yui et al.1994, Rinaudo 2006, Kurita 2001. Such isotherms are often encountered when the adsorbate has a strong intermolecular attraction for the surface of the adsorbent. The L 2 shape of the isotherm observed in the present care implies that Rhodamine dye molecules must have been strongly attached to the Chitosan-Selenium nanoparticle. Langmuir equation can be written in four linearized types, the Langmuir constants q m and K L values can be calculated by plotting between type 1-C e /q e versus C e , type 2 -1/q e versus 1/C e , type 3q e versus q e /C e , and type 4q e /C e versus q e , Langmuir isotherms, respectively. The linear method does not test whether the experimental data are linear. It assumes the experimental data were linear and predicts the slope and intercepts that make a straight line that predicts the best-fit of experimental equilibrium data (Yoshida & Takemori 1997, Gupta et al. 1989, Giunchedi et al. 1998, Ghosh & Bhattacharyya 2002. The linear method assumes that the scatter of points around the line follows a Gaussian distribution and the error distribution is the same at every value of X. The linear method just predicts the Y for the corresponding X. It considers only the error distribution f specific dye uptake at different pH (Chitosan-Selenium nanoparticle) with e concentration.
therm isotherm (1916, 1918) has found successful application to many other real sorption it can be used to explain the sorption of Rhodamine dye into Chitosan-Selenium basic assumption of the Langmuir theory is that sorption takes place at specific adsorbent (Kawamura et al. 1993, Lee& Low 1987, Wei et al.1992. The data the adsorption experiment conducted in the present investigation were fitted in amine dye concentrations, dosages, pH, and temperature in the isotherm equation.     Rhodamine dye concentration.

Langmuir Isotherm
The Langmuir isotherm (1916Langmuir isotherm ( , 1918 has found successful application to many other real sorption processes and it can be used to explain the sorption of Rhodamine dye into Chitosan-Selenium nanoparticle. A basic assumption of the Langmuir theory is that sorption takes place at specific sites within the adsorbent (Kawamura et al. 1993, Lee& Low 1987, Wei et al.1992. The data obtained from the adsorption experiment conducted in the present investigation were fitted in different Rhodamine dye concentrations, dosages, pH, and temperature in the isotherm equation. The saturation monolayer can be represented by the expression (2).

Langmuir Isotherm
The Langmuir isotherm (1916Langmuir isotherm ( , 1918 has found successful application to many other real sorption processes and it can be used to explain the sorption of Rhodamine dye into Chitosan-Selenium nanoparticle. A basic assumption of the Langmuir theory is that sorption takes place at specific sites within the adsorbent (Kawamura et al. 1993, Lee& Low 1987, Wei et al.1992. The data obtained from the adsorption experiment conducted in the present investigation were fitted in different Rhodamine dye concentrations, dosages, pH, and temperature in the isotherm equation. The saturation monolayer can be represented by the expression (2).

Langmuir Isotherm
The Langmuir isotherm (1916Langmuir isotherm ( , 1918 has found successful application to many other real sorption processes and it can be used to explain the sorption of Rhodamine dye into Chitosan-Selenium nanoparticle. A basic assumption of the Langmuir theory is that sorption takes place at specific sites within the adsorbent (Kawamura et al. 1993, Lee& Low 1987, Wei et al.1992. The data obtained from the adsorption experiment conducted in the present investigation were fitted in different Rhodamine dye concentrations, dosages, pH, and temperature in the isotherm equation. The saturation monolayer can be represented by the expression (2).

Langmuir Isotherm
The Langmuir isotherm (1916Langmuir isotherm ( , 1918 has found successful application to many other real sorption processes and it can be used to explain the sorption of Rhodamine dye into Chitosan-Selenium nanoparticle. A basic assumption of the Langmuir theory is that sorption takes place at specific sites within the adsorbent (Kawamura et al. 1993, Lee& Low 1987, Wei et al.1992. The data obtained from the adsorption experiment conducted in the present investigation were fitted in different Rhodamine dye concentrations, dosages, pH, and temperature in the isotherm equation. The saturation monolayer can be represented by the expression (2).

Langmuir Isotherm
The Langmuir isotherm (1916Langmuir isotherm ( , 1918 has found successful application to many other real sorption processes and it can be used to explain the sorption of Rhodamine dye into Chitosan-Selenium nanoparticle. A basic assumption of the Langmuir theory is that sorption takes place at specific sites within the adsorbent (Kawamura et al. 1993, Lee& Low 1987, Wei et al.1992. The data obtained from the adsorption experiment conducted in the present investigation were fitted in different Rhodamine dye concentrations, dosages, pH, and temperature in the isotherm equation. The saturation monolayer can be represented by the expression (2).

Langmuir Isotherm
The Langmuir isotherm (1916Langmuir isotherm ( , 1918 has found successful application to many other real sorption processes and it can be used to explain the sorption of Rhodamine dye into Chitosan-Selenium nanoparticle. A basic assumption of the Langmuir theory is that sorption takes place at specific sites within the adsorbent (Kawamura et al. 1993, Lee& Low 1987, Wei et al.1992. The data obtained from the adsorption experiment conducted in the present investigation were fitted in different Rhodamine dye concentrations, dosages, pH, and temperature in the isotherm equation. The saturation monolayer can be represented by the expression (2). . .

Linear Regression of Langmuir Isotherm -Chitosan-Selenium Nanocomposite-Rhodamine
Dye distribution is the same at every value of X. The linear method just predicts the Y for the corresponding X. It considers only the error distribution along the Y-axis irrespective of the corresponding X-axis resulting in the different determined parameters.    corresponding X. It considers only the error distribution along the Y-axis irrespective of the corresponding X-axis resulting in the different determined parameters. corresponding X-axis resulting in the different determined parameters. corresponding X-axis resulting in the different determined parameters.                along the Y-axis irrespective of the corresponding X-axis resulting in the different determined parameters.

Freundlich Isotherm-Rhodamine Dye-Chitosan-Selenium Nanoparticle
Freundlich (1906)  ious constants, associated with the isotherm are the intercept, which is roughly on the indicator of sorption (kf), and the slope (1/n) sorption intensity values recorded in Table 2 from Equations 8 and 9. Freundlich has been illustrated to be a special case of heterogeneous surface energies and it can be easily extended to e. It has been stated by Krajewska (2005)& Kawamura et al.(1997, that magnitude of the exponent 1/n s the favourability and capacity of the adsorbent/adsorbate system. The values n>1 represent favourable on conditions. In most cases, the exponent between 1<n<10 shows beneficial adsorption.
Freundlich isotherm for the adsorption of Rhodamine dye using Chitosan-Seleniumnanocomposite at t Dosages with dye concentration.
Freundlich isotherm for the adsorption of Rhodamine dye using Chitosan-Seleniumnanocomposite at t Temperatures with dye concentration. ... (9) The various constants, associated with the isotherm are the intercept, which is roughly on the indicator of sorption capacity (kf), and the slope (1/n) sorption intensity values recorded in Table 2 from Equations 8 and 9. Freundlich isotherm has been illustrated to be a special case of heterogeneous surface energies and it can be easily extended to this case. It has been stated by Krajewska (2005) & Kawamura et al.(1997), that magnitude of the exponent 1/n indicates the favourability and capacity of the adsorbent/adsorbate system. The values n>1 represent favourable adsorption conditions. In most cases, the exponent between 1<n<10 shows beneficial adsorption.
Mechanism of adsorption according to the process of adsorption occurs either in a single step or in the combination of the steps such as film or external diffusion, pore diffusion, surface diffusion, and adsorption on the pore surface. It was also reported that adsorption on the adsorbent surface proceeds in three steps: (1) migration to the surface, (2) dissociation (or deprotonation) of complexes in an aqueous solution. Once equilibrium is attained, the migration of the solute species from the solution stops. Under this situation, it is possible to measure the magnitude of the distribution of the solute species between the liquid and solid phases. The magnitude of this kind of distribution is a measure of the efficiency of the chosen adsorbent in the adsorbate species. When a powdered solid adsorbent material is made in contact with a solution containing dyes, the dyes first migrate from the bulk solution to the surface of the liquid film. This surface exerts a diffusion barrier.
This barrier may be very significant or less significant (Gupta et al. 2005, Karthikeyan et al. 2010. The involvement of a significant quantum of diffusion barrier indicates the dominant role taken up by the film diffusion in the adsorption process. Furthermore, the rate of an adsorption process is controlled either by external diffusion, internal diffusion, or by both types of diffusions. The external diffusion controls    ... (9) nts, associated with the isotherm are the intercept, which is roughly on the indicator of sorption he slope (1/n) sorption intensity values recorded in Table 2 from Equations 8 and 9. Freundlich illustrated to be a special case of heterogeneous surface energies and it can be easily extended to en stated by Krajewska (2005)& Kawamura et al.(1997, that magnitude of the exponent 1/n rability and capacity of the adsorbent/adsorbate system. The values n>1 represent favourable ns. In most cases, the exponent between 1<n<10 shows beneficial adsorption.
isotherm for the adsorption of Rhodamine dye using Chitosan-Seleniumnanocomposite at ith dye concentration.
isotherm for the adsorption of Rhodamine dye using Chitosan-Seleniumnanocomposite at ures with dye concentration.    the migration of the solute species from the solution to the boundary layer of the liquid phase. However, the internal diffusion controls the transfer of the solute species from the external surface of the adsorbent to the internal surface of the pores of the adsorbent material (Karthikeyan et al. 2010 andGupta et al. 2003b). It is now well established, that during the adsorption of dye over a porous adsorbent, the following three consecutive steps were taken place (Crank 1975 andKarthikeyan et al. 2010) (i) Transport of the ingoing adsorbate ions to the external surface of the adsorbent (film diffusion), (ii) Transport of the adsorbate ions within the pores of the adsorbent except for a small amount of adsorption, which occurs on the external surface (particle diffusion) and (iii) Adsorption of the ingoing adsorbate ions on the interior surface of the adsorbent (Weber &Morris 1963 andKarthikeyan et al. 2010).

CONCLUSION
In this study, the ever-increasing problem of dye pollutants and ways of dye remediation has been discussed. The environment-friendly technique of adsorption is brought into the light. The enhanced properties of the nanomaterials because of their small size and ways of synthesizing them have been summed up. The plant Justicia adhatoda leaf extract is used to produce Chitosan-Selenium nanocomposite which acts as good reducing agents for the preparation of Chitosan-Selenium nanocomposite. Likewise, chitosanselenium nanocomposite was prepared by a simple step. UV-. Vis spectra show characteristics peak for Chitosan-Selenium nanocomposite. XRD shows the crystalline structure of Chitosan-Selenium nanocomposite, whereas the amorphous structure of chitosan-selenium nanocomposite indicates chitosan strongly coated with selenium nanoparticles. FTIR shows that functional groups responsible for the synthesis of the process are phenols, carboxylic acid, primary amine and nitro compounds, etc. for both nanoparticles. The average particle size range was noted for Chitosan-Selenium nanocomposite as 87-152 nm, respectively. Adsorption depends upon the chemical nature of the material, various physicochemical experimental conditions such as solution pH, adsorbent dosage, temperature. Adsorption technology provides an attractive pathway for further research and improvement in more efficient nanoparticles, with higher adsorption capacity, for numerous dyes to eliminate the dyes discharged from various industries and thus reduce the contamination of water. Dosages (