Review
Application of low-cost adsorbents for dye removal – A review

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Abstract

Dyes are an important class of pollutants, and can even be identified by the human eye. Disposal of dyes in precious water resources must be avoided, however, and for that various treatment technologies are in use. Among various methods adsorption occupies a prominent place in dye removal. The growing demand for efficient and low-cost treatment methods and the importance of adsorption has given rise to low-cost alternative adsorbents (LCAs). This review highlights and provides an overview of these LCAs comprising natural, industrial as well as synthetic materials/wastes and their application for dyes removal. In addition, various other methods used for dye removal from water and wastewater are also complied in brief. From a comprehensive literature review, it was found that some LCAs, in addition to having wide availability, have fast kinetics and appreciable adsorption capacities too. Advantages and disadvantages of adsorbents, favourable conditions for particular adsorbate–adsorbent systems, and adsorption capacities of various low-cost adsorbents and commercial activated carbons as available in the literature are presented. Conclusions have been drawn from the literature reviewed, and suggestions for future research are proposed.

Introduction

Saving water to save the planet and to make the future of mankind safe is what we need now. With the growth of mankind, society, science, technology our world is reaching to new high horizons but the cost which we are paying or will pay in near future is surely going to be too high. Among the consequences of this rapid growth is environmental disorder with a big pollution problem. Besides other needs the demand for water (“Water for People Water for Life” United Nations World Water Development Report UNESCO) has increased tremendously with agricultural, industrial and domestic sectors consuming 70, 22 and 8% of the available fresh water, respectively and this has resulted in the generation of large amounts of wastewater (Helmer and Hespanhol, 1997, Lehr et al., 1980, Nemerrow, 1978) containing a number of ‘pollutants’. One of the important class of the pollutants is dyes, and once they enter the water it is no longer good and sometimes difficult to treat as the dyes have a synthetic origin and a complex molecular structure which makes them more stable and difficult to be biodegraded (Forgacs et al., 2004, Rai et al., 2005).

Mankind has used dyes for thousands of years (Christie, 2007) and the earliest known use of a colourant is believed to be by Neanderthal man about 1,80,000 years ago. However, the first known use of an organic colourant was much later, being nearly 4000 years ago, when the blue dye indigo was found in the wrappings of mummies in Egyptian tombs (Gordon and Gregory, 1983). Till the late nineteenth century, all the dyes/colourants were more or less natural with main sources like plants, insects and mollusks, and were generally prepared on small scale. It was only after 1856 that with Perkin's historic discovery (Hunger, 2003, Venkataraman, 1965) of the first synthetic dye, mauveine, that dyes were manufactured synthetically and on a large scale.

Dye molecules comprise of two key components: the chromophores, responsible for producing the colour, and the auxochromes, which can not only supplement the chromophore but also render the molecule soluble in water and give enhanced affinity (to attach) toward the fibers. Dyes exhibit considerable structural diversity and are classified in several ways. These can be classified (Hunger, 2003) both by their chemical structure and their application to the fiber type. Dyes may also be classified on the basis of their solubility: soluble dyes which include acid, mordant, metal complex, direct, basic and reactive dyes; and insoluble dyes including azoic, sulfur, vat and disperse dyes. Besides this, either a major azo linkage or an anthraquinone unit also characterizes dyes chemically. It is worthwhile noting that the azo dyes are the one most widely used and accounts 65–70% of the total dyes produced. Though, the classification of dyes on basis of structure is an appropriate system and has many advantages, like it readily identifies dyes as belonging to a group and having characteristic properties, e.g., azo dyes (strong, good all-round properties, cost-effective) and anthraquinone dyes (weak, expensive), there are a manageable number of chemical groups (about a dozen). Besides these, both the synthetic dye chemist and the dye technologist use this classification most widely. However, the classification based on application is advantageous before considering chemical structures in detail because of the complexities of the dye nomenclature from this type of system. It is also worth to point that classification by application is the principal system adopted by the Colour Index (C.I.). In the present review we will try to use the dye names based on their application or their C.I. name/number. This system includes the name of the dye class, its hue, and a number. A five digit C.I. number is assigned to a dye when its chemical structure has been disclosed by the manufacturer. It is also worth to note here that though a dye has a C.I. number, the purity and precise chemical constitution may vary depending upon the name. An example of dye acid blue 92 is given in Fig. 1 (Sabnis, 2008).

Some properties of dyes classified on their usage (Christie, 2007, Hunger, 2003) are discussed in brief here.

Acid Dyes: used for nylon, wool, silk, modified acrylics, and also to some extent for paper, leather, ink-jet printing, food, and cosmetics. They are generally water soluble. The principal chemical classes of these dyes are azo (including premetallized), anthraquinone, triphenylmethane, azine, xanthene, nitro and nitroso.

Cationic (Basic) Dyes: used for paper, polyacrylonitrile, modified nylons, modified polyesters, cation dyeable polyethylene terephthalate and to some extent in medicine too. Originally they were used for silk, wool, and tannin-mordanted cotton. These water-soluble dyes yield coloured cations in solution and that's why are called as cationic dyes. The principal chemical classes are diazahemicyanine, triarylmethane, cyanine, hemicyanine, thiazine, oxazine and acridine.

Disperse Dyes: used mainly on polyester and to some extent on nylon, cellulose, cellulose acetate, and acrylic fibers. These are substantially water-insoluble nonionic dyes used for hydrophobic fibers from aqueous dispersion. They generally contain azo, anthraquinone, styryl, nitro, and benzodifuranone groups.

Direct Dyes: used in the dyeing of cotton and rayon, paper, leather, and, to some extent to nylon. They are water-soluble anionic dyes, and, when dyed from aqueous solution in the presence of electrolytes have high affinity for cellulosic fibers. Generally the dyes in this class are polyazo compounds, along with some stilbenes, phthalocyanines and oxazines.

Reactive Dyes: generally used for cotton and other cellulosics, but are also used to a small extent on wool and nylon. These dyes form a covalent bond with the fiber and contain chromophoric groups such as azo, anthraquinone, triarylmethane, phthalocyanine, formazan, oxazine, etc. Their chemical structures are simpler, absorption spectra show narrower absorption bands, and the dyeings are brighter making them advantageous over direct dyes.

Solvent Dyes: used for plastics, gasoline, lubricants, oils, and waxes. These dyes are solvent soluble (water insoluble) and generally nonpolar or little polar, i.e., lacking polar solubilizing groups such as sulfonic acid, carboxylic acid, or quaternary ammonium. The principal chemical classes are predominantly azo and anthraquinone, but phthalocyanine and triarylmethane are also used.

Sulfur Dyes: used for cotton and rayon and have limited use with polyamide fibers, silk, leather, paper, and wood. They have intermediate structures and though they form a relatively small group of dyes the low cost and good wash fastness properties make this class important from an economic point of view.

Vat Dyes: used for cotton mainly to cellulosic fibers as soluble leuco salts and for rayon and wool too. These water-insoluble dyes are with principal chemical class containing anthraquinone (including polycyclic quinones) and indigoids.

Besides these, there are some other classes too like azoic having azo groups used for cotton and other cellulosic materials; fluorescent brighteners having stilbene, pyrazoles, coumarin and naphthalimides used for soaps and detergents, fibers, oils, paints, and plastics and mordant having azo and anthraquinone used for wool, leather, natural fibers after pretreating with metals and anodized aluminium.

Overall at present there are more than 100,000 commercial dyes with a rough estimated production of 7 × 105–1 × 106 tons per year (Christie, 2007, Hunger, 2003, Husain, 2006, Meyer, 1981, Zollinger, 1987). Of such a huge production the exact data on the quantity of dyes discharged in environment is not available. However, it is reported that 10–15% of the used dyes enter the environment through wastes (Hai et al., 2007, Husain, 2006). The big consumers of dyes are textile, dyeing, paper and pulp, tannery and paint industries, and hence the effluents of these industries as well as those from plants manufacturing dyes tend to contain dyes in sufficient quantities. Dyes are considered an objectionable type of pollutant because they are toxic (Bae and Freeman, 2007, Christie, 2007, Combes and Havelandsmith, 1982, Nemerow and Doby, 1958) generally due to oral ingestion and inhalation, skin and eye irritation, and skin sensitization leading to problems like skin irritation and skin sensitization and also due to carcinogenicity (Christie, 2007, Hatch and Maibach, 1999, Rai et al., 2005). They impart colour to water which is visible to human eye and therefore, highly objectionable on aesthetic grounds. Not only this, they also interfere with the transmission of light and upset the biological metabolism processes which cause the destruction of aquatic communities present in ecosystem (Kuo, 1992, Walsh et al., 1980). Further, the dyes have a tendency to sequester metal and may cause microtoxicity to fish and other organisms (Walsh et al., 1980). As such it is important to treat coloured effluents for the removal of dyes.

For this various methodologies have been presented and even reviewed too (Aksu, 2005, Banat et al., 1996, Crini, 2006, Crini and Badot, 2008, Delee et al., 1998, dos Santos et al., 2007, Forgacs et al., 2004, Fu and Viraraghavan, 2001a, Hai et al., 2007, Kandelbauer and Guebitz, 2005, McMullan et al., 2001, Ozyurt and Atacag, 2003, Pearce et al., 2003, Rai et al., 2005, Robinson et al., 2001, Sanghi and Bhattacharya, 2002, Slokar and Majcen Le Marechal, 1998, Stolz, 2001, van der Zee and Villaverde, 2005, Vandevivere et al., 1998, Wesenberg et al., 2003, Wojnarovits and Takacs, 2008). Some of these are discussed in the subsequent paragraphs.

Section snippets

Methods of dye removal

Few decades earlier, the dyes selection, application and use were not given a major consideration with respect to their environmental impact. Even the chemical composition of half of the dyes used in the industry was estimated to be unknown. With the growing concern on health mainly on aesthetic grounds, it was more from 80s that people started paying much attention to the dye wastes too. In the last few years, however, more information on the environmental consequences of dyestuff usage has

Adsorption and ion exchange

In addition to already mentioned methods, the adsorption process has been widely used for colour removal. Adsorption is one of the processes, which besides being widely used for dye removal also has wide applicability in wastewater treatment (Bansal and Goyal, 2005, Danis et al., 1998, Freeman, 1989, Imamura et al., 2002, Liapis, 1987, Mantell, 1951, Mattson and Mark, 1971, Pirbazari et al., 1991, Quignon et al., 1998, Weber Jr. et al., 1970). The term adsorption refers to a process wherein a

Low-cost alternative adsorbents

Natural materials or the wastes/by-products of industries or synthetically prepared materials, which cost less and can be used as such or after some minor treatment as adsorbents are generally called low-cost adsorbents (LCAs). A protocol based on the numerous studies for the development, utilization and application of low-cost adsorbents generally adopted by researchers has been suggested by Gupta et al. (in press). The LCAs as reported in literature are usually called substitutes for

LCA efficiency and cost comparison

Efficiency (or adsorption capacity as discussed in the article) of a material is an important aspect as understood by the studies reported in preceding paragraphs, but it is (should be) relative as it need to be compared with some standard adsorbent like AC or some other one closer to the material under investigation. Besides this, adsorbent cost is an important factor and may be helpful in comparing the materials; however, it is seldom reported in the research papers. Fig. 3 and Table 1, Table

Combination of methodologies/techniques

Some workers have used the methods in conjunction with each other or some other process. A combination of adsorption and nanofiltration (NF) was adopted for the treatment of a textile dyehouse effluent containing a mixture of two reactive dyes (Chakraborty et al., 2005). The effluent stream was first treated in a batch adsorption process with a waste carbonaceous material (sawdust) as an adsorbent to reduce the dye concentration of the effluent by about 83% for reactive red CNN and 93% for

Conclusions and future perspectives

The literature reviewed revealed the fact that there has been a high increase in production and utilization of dyes in last few decades resulting in a big threat of pollution. It is worthwhile noting that the removal of dyes can be done by various techniques; however, there exists no such methodology which can successfully remove all types of dyes at low cost. The literature survey results and the methods discussed above lead us to the conclusion that for removal of dyes either adsorption alone

References (475)

  • Z. Aksu

    Application of biosorption for the removal of organic pollutants: a review

    Process Biochem.

    (2005)
  • Z. Aksu et al.

    A comparative study on the biosorption characteristics of some yeasts for Remazol Blue reactive dye

    Chemosphere

    (2003)
  • Z. Aksu et al.

    Equilibrium and kinetic modelling of biosorption of Remazol Black B by Rhizopus arrhizus in a batch system: effect of temperature

    Process Biochem.

    (2000)
  • Z. Aksu et al.

    Biosorption of reactive dyes on the green alga Chlorella vulgaris

    Process Biochem.

    (2005)
  • A. Akyol et al.

    Photocatalytic decolorization of Remazol Red RR in aqueous ZnO suspensions

    Appl. Catal., B

    (2004)
  • N. Al-Bastaki

    Removal of methyl orange dye and Na2SO4 salt from synthetic waste water using reverse osmosis

    Chem. Eng. Process

    (2004)
  • Y. Al-Degs et al.

    Effect of carbon surface chemistry on the removal of reactive dyes from textile effluent

    Water Res.

    (2000)
  • M.A. Al-Ghouti et al.

    The removal of dyes from textile wastewater: a study of the physical characteristics and adsorption mechanisms of diatomaceous earth

    J. Environ. Manage.

    (2003)
  • Z. Al-Qodah

    Adsorption of dyes using shale oil ash

    Water Res.

    (2000)
  • M. Alkan et al.

    Adsorption kinetics and thermodynamics of an anionic dye onto sepiolite

    Microporous Mesoporous Mater.

    (2007)
  • S. Allen et al.

    The adsorption of acid dye onto peat from aqueous solution-solid diffusion model

    J. Colloid Interface Sci.

    (1988)
  • S. Allen et al.

    Multi-component sorption isotherms of basic dyes onto peat

    Environ. Pollut.

    (1988)
  • S.J. Allen et al.

    Comparison of optimised isotherm models for basic dye adsorption by kudzu

    Bioresour. Technol.

    (2003)
  • S.J. Allen et al.

    Adsorption isotherm models for basic dye adsorption by peat in single and binary component systems

    J. Colloid Interface Sci.

    (2004)
  • S.K. Alpat et al.

    The adsorption kinetics and removal of cationic dye, Toluidine Blue O, from aqueous solution with Turkish zeolite

    J. Hazard. Mater.

    (2008)
  • G. Annadurai et al.

    Use of cellulose-based wastes for adsorption of dyes from aqueous solutions

    J. Hazard. Mater.

    (2002)
  • G. Annadurai et al.

    Adsorption of reactive dye from an aqueous solution by chitosan: isotherm, kinetic and thermodynamic analysis

    J. Hazard. Mater.

    (2008)
  • M.C. Annesini et al.

    Adsorption of organic compounds onto activated carbon

    Water Res.

    (1987)
  • M. Arami et al.

    Removal of dyes from colored textile wastewater by orange peel adsorbent: equilibrium and kinetic studies

    J. Colloid Interface Sci.

    (2005)
  • M. Arami et al.

    Equilibrium and kinetics studies for the adsorption of direct and acid dyes from aqueous solution by soy meal hull

    J. Hazard. Mater.

    (2006)
  • B. Armagan et al.

    Equilibrium studies on the adsorption of reactive azo dyes into zeolite

    Desalination

    (2004)
  • G. Atun et al.

    Adsorptive removal of methylene blue from colored effluents on fuller's earth

    J. Colloid Interface Sci.

    (2003)
  • S.A. Avlonitis et al.

    Simulated cotton dye effluents treatment and reuse by nanofiltration

    Desalination

    (2008)
  • A. Aygun et al.

    Production of granular activated carbon from fruit stones and nutshells and evaluation of their physical, chemical and adsorption properties

    Microporous Mesoporous Mater.

    (2003)
  • S. Babel et al.

    Low-cost adsorbents for heavy metals uptake from contaminated water: a review

    J. Hazard. Mater.

    (2003)
  • S. Babel et al.

    Cr(VI) removal from synthetic wastewater using coconut shell charcoal and commercial activated carbon modified with oxidizing agents and/or chitosan

    Chemosphere

    (2004)
  • J.-S. Bae et al.

    Aquatic toxicity evaluation of new direct dyes to the Daphnia magna

    Dyes Pigments

    (2007)
  • M. Bagane et al.

    Elimination d'un colorant des effluents de l'industrie textile par adsorption

    Ann. Chim. Sci. Mat.

    (2000)
  • S.E. Bailey et al.

    A review of potentially low-cost sorbents for heavy metals

    Water Res.

    (1999)
  • I.M. Banat et al.

    Microbial decolorization of textile-dye containing effluents: a review

    Bioresour. Technol.

    (1996)
  • F. Banat et al.

    Evaluation of the use of raw and activated date pits as potential adsorbents for dye containing waters

    Process Biochem.

    (2003)
  • E.R. Bandala et al.

    Photocatalytic decolourisation of synthetic and real textile wastewater containing benzidine-based azo dyes

    Chem. Eng. Process.

    (2008)
  • B.E. Barragan et al.

    Biodegradation of azo dyes by bacteria inoculated on solid media

    Dyes Pigments

    (2007)
  • F.A. Batzias et al.

    Dye adsorption by calcium chloride treated beech sawdust in batch and fixed-bed systems

    J. Hazard. Mater.

    (2004)
  • F.A. Batzias et al.

    Dye adsorption by prehydrolysed beech sawdust in batch and fixed-bed systems

    Bioresour. Technol.

    (2007)
  • F.A. Batzias et al.

    Simulation of dye adsorption by beech sawdust as affected by pH

    J. Hazard. Mater.

    (2007)
  • M.A. Behnajady et al.

    Kinetic study on photocatalytic degradation of C.I. Acid Yellow 23 by ZnO photocatalyst

    J. Hazard. Mater.

    (2006)
  • M. Bele et al.

    Adsorption of cetyltrimethylammonium bromide on carbon black from aqueous solution

    Carbon

    (1998)
  • Y.E. Benkli et al.

    Modification of organo-zeolite surface for the removal of reactive azo dyes in fixed-bed reactors

    Water Res.

    (2005)
  • K.G. Bhattacharyya et al.

    Adsorption characteristics of the dye, Brilliant Green, on Neem leaf powder

    Dyes Pigments

    (2003)
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