Adsorption performance of Cr(VI)-imprinted poly(4-VP-co-MMA) supported on activated Indonesia (Ende-Flores) natural zeolite structure for Cr(VI) removal from aqueous solution

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Abstract

The adsorption performance of Cr(VI) on the Cr(VI)-imprinted poly(4-VP-co-MMA) (IIP) supported on Activated Indonesia (Ende-Flores) natural zeolite (ANZ) structure for Cr(VI) removal from aqueous solution have been studied. Cr(VI)-imprinted-poly(4-VP-co-MMA)-ANZ (IIP-ANZ) was synthesized using Cr(VI) as a template, 4-vinylphiridine (4-VP) as a complex agent, methyl methacrylate (MMA) as a monomer agent, ethylene glycol dimethylacrylate (EGDMA) as cross-linker and benzoyl peroxide (BPO) as an initiator. XRD, FTIR, SEM-EDX and BET was performed to characterize the synthesized materials. The maximum adsorption capacity was 4.365 mg/g adsorbent at pH 2, 30 min contact time, under 303 K respectively. Five kinetic and four isotherm models were used to find out the reaction rate of Cr(VI) adsorption processes on this adsorbent. Under the competitive condition, the adsorption capacity of this adsorbent for Cr(VI) is greater than Cr(III), Mn(II) or Ni(II) ions but it less selective if present of Pb(II) ion. Moreover, the reusability of the IIP-ANZ was tested for five times and no significant loss in adsorption capacity observed.

Introduction

Water pollution was increased in last view decade because of industrial activity. One of dangerous pollutant is Cr(VI) ion. It’s believed to cause cancer, carcinogenic and another health problem such as skin irritation, dermatitis, asthma, and a bronchogenic carcinoma for human body and mutagenic for living organism even in low concentration [1], [2], [3], [4]. Cr(VI) has been more concerned by the researchers because of its negative impact on a living organism and aquatic ecosystem. There are many technologies have been developed to remove Cr(VI) from water or industrials wastewater such as ion exchange [5], membrane separation [6] and adsorption [7]. The adsorption process is a most used method for removing an heavy metal from water and wastewater because of its low economic cost and easy use. There are many adsorbents were used and reported to remove Cr(VI) from water and wastewater as well [7] but their selectivity is reduced.

Natural zeolite is one of adsorbent that can be used to remove Cr(VI) from the aquatic environment because zeolites tuffs have been found in many areas of the world. There are many natural zeolites identified in e prevalent forms in the world such as clinoptilolite, mordenite, phillipsite, chabazite, stilbite, analcime and laumontite whereas offretite, paulingite, barrerite and mazzite, are much rarer. Among the zeolites, clinoptilolite is the most abundant natural zeolite and widely used in the world [8]. Surface of natural zeolites normally possess a negatively charged and therefore this only effective for cation exchange properties. It causes low capacity and selectivity adsorption if natural zeolite directly use for adsorption of Cr(VI) because Cr(VI) has a negative charged properties too. For that natural zeolite must be modified to capable for adsorption anion. There are many researchers to improve capacity and selective adsorption of natural zeolite to remove Cr(VI) such as modification natural zeolite with surfactant [9], magnetic oxide ion [30], polyhexamethylene-guanidine-modified natural zeolitic [10]. Modification natural zeolite with polymer compound as a particular class of organo-modified natural zeolites, which are mechanically and chemically stable in various aqueous environments [11].

Ion imprinting polymer (IIP) is a good polymerizing technique to produce ionic recognition material with high selectivity and affinity for the template ion target. Currently, many application of IIP for removal Cr(VI) has been reported [12]. However ion imprinting polymer is high-cost material, so it used in the preparation and preconcentration ion sample. To use in water and wastewater treatment, IIP must be reduced to the low-cost material. Therefore modification natural zeolite with the ordered ion imprinted polymer is promising to get low-cost adsorbent material with high selectivity and capacity for adsorption of Cr(VI).

In spite of having high selectivity, IIP was prepare by conventional methods (bulk) polimerization) have some limitations, such as template removal is not complete, slow mass transfer, heterogeneous distribution of the binding site, low rigid material [13]. Many composite material has been developed to resolve the disadvantages of IIP materials [14]. Also, the composite adsorbent material have been widely applied to adsorption of Cr(VI) from water sample in recent years because of their merits, low cost and strong adsorption properties [15], [16]. However, ion imprinted polymer support on natural zeolite still has a limitation in literature report. Currently, preparation of magnetic natural zeolite polymer composite for Cr(VI) adsorption have been studied [17].

In this paper, we will report one of our research about preparation of composite adsorbent base on ion imprinted polymer support on Indonesia (Ende-Flores) natural zeolite for Cr(VI) adsorption from aqueous solution. From another part of our research, it has been known that Indonesia (Ende-Flores) natural zeolite was identified as mordenite type, and also, we have been modified to become a natural zeolites with acid properties, then used to adsorption of Cr(VI) from aqueous solution [18].

The objective of this work is preparing the Cr(VI)-imprinted-4-VP-co-MMA-Indonesia (Ende-Flores) natural zeolite (IIP-ANZ) for the Cr(VI) selective adsorption from aqueous solution. The Cr(VI)-imprinted-4-VP-co-MMA-Indonesia (Ende-Flores) natural zeolite (IIP-ANZ) was prepared from Cr(VI) as template, 4-vinylphiridine (4-VP) as complex agent, methyl methacrylate (MMA) as functional monomer, Ethylene glycol dimethyl acrylate (EGDMA) as cross linker agent, benzoyl peroxide (BPO) as initiator and ethanol/acetone as porogen. The optimation of parameters adsorption such as adsorbent amount, initial pH of sample solution, contact time and temperature were studied. Adsorption kinetic, isotherm and thermodynamic, selectivity, reusability were also discussed.

Section snippets

Reagent and materials

Potassium dichromate (K2Cr2O7), Sodium hydroxide (NaOH), 1,5-diphenyl carbazide, sulphuric acid (H2SO4), hydrochloric acid (HCl), acetone, nitric acid, NH4Cl, CrCl3. 6H2O, Ni2SO4, Mn2SO4, Pb(NO3)2, 4-vinyl pyridine (4-VP), methyl methacrylate (MMA), ethylene glycol dimethacarylate (EGDMA, benzoyl peroxide (BPO) were purchased from Merck (Singapore) and Sigma Aldrich (Singapore). Acid activated of Indonesia (Ende-Flores) natural zeolite (ANZ) was produced in our lab.

Preparation of Cr(VI)-poly(4-VP-co-MMA)-ANZ

To synthesize

XRD characterization

XRD spectra (Fig. 1) confirm that the crystal phase poly 4-VP-co-MMA was changed from amorphous phase to semi-crystalline phase after polymerization together with ANZ. Other while the structure of ANZ was not exchanged after polymerization processes. Fig. 1 confirmed by the characteristic peak of mordenite and quartz such as 2θ = 9.72, 13.40, 19.68, 22.28, 25.63 and 27.64 for mordenite and 2θ = 21.03, 26.62 and 36.70 for quartz (spectra was comparing with COD data number 96–900-3355 and

Conclusions

An another new adsorbent has been successfully synthesized from Indonesia (Ende-Flores) natural zeolite with imprinting polymer materials for Cr(VI) selective adsorption from aqueous solution. In this study, optimum experimental condition to maximize the adsorption capacity of Cr(VI) was taken place on initial concentration of 50 mL sample (K2Cr2O7) 14 mg/L, adsorbent amount is 0.1 g, pH = 2, contact time is 30 min and temperature condition is 303 K. The temperature has an adverse effect on

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