On the utilization of a lignocellulosic waste as an excellent dye remover: Modification, characterization and mechanism analysis
Introduction
Pollution of the water sources by organic and inorganic contaminants is a major concern in many industrialized countries. The removal of these from aquatic environment by ecofriendly technologies is one of the important issues in the field of water treatment because of their possible toxic and hazardous effects. In recent years, the use of biosorption process for the treatment of effluents is receiving more attention.
Biosorption potential of a biomaterial is based on the interactions between contaminants and hydroxyl, carboxyl, phosphoryl and other charged groups localized on the cell wall structure of the organisms composed of macromolecules such as heteropolysaccharides, proteins and lipids. Adsorption, complexation, and chelatation and ion exchange can play a role in the biosorption mechanisms [1], [2]. Recently, utilization of different types of biosorbents derived from fungi, yeast, algae, bacteria, chitosan and lignocellulosic materials in pollutant removal process has been extensively reviewed by several researchers [3], [4], [5]. Among the commonly available sorbents, biomasses obtained as industrial by-products have been shown more convenient in practical applications due to their low- or no-costs, easy handling and good biosorption performances. Hence, the use of these biomaterials for water treatment has received much more attention in recent years. Various industrial by-products or wastes such as crab shells [6], Streptoverticillium cinnamoneum [7], olive pomace [8], [9], olive stone [10], Citrus sinensis [11], Pleurotus mutilus [12], Capsicum annuum seeds [13], sugarcane bagasse [14], Phaseolus vulgaris [15] and beer yeast [16] have been successfully applied for the removal of organic and inorganic contaminants.
Sugar beet pulp, a lignocellulosic by-product of the sugar refining industry is produced annually in large quantities. Cellulose, hemicelluloses and pectin are the main constituents of its polysaccharide content. The pectin substances and hemicelluloses hinder the utilization of this by product in the paper production. The typical end-use of this by-product was in animal feed manufacture [17], [18] apart from some specific alternative uses such as matrix in bioethanol production [19], supplemental substrate [20] source of pectin [21] and cellulose microfibrils [18]. Besides, although some reports are available in the literature concerning the heavy metal removal ability of the sugar beet pulp [22], [23], [24], a limited number of studies have so far been focused on the use of this by-product for decolorization of dye contaminated waters [25], [26], [27].
In the present communication, decolorization potential of sugar beet pulp was significantly improved by a chemical modification. Cetil trimethylammonium bromide (CTAB) was used as modification agent and high biosorption yields were obtained by small amounts of modified biosorbent. Design parameters in batch and continuous modes were investigated. Modeling and characterization studies were also conducted in addition to regeneration and application studies.
Section snippets
Biosorbent modification and dye solutions
The sugar beet pulp was obtained from the Sugar factory in Eskişehir, Turkey. It was washed repeatedly with deionized water and left to dry in an oven at 60 °C. The dried solid waste was grounded in a laboratory mill and <212 μm particle size was selected for biosorption and modification studies.
The powdered pulp sample (4.0 g) was treated with 250 mL of (%1 (w/v)) CTAB solutions. After magnetically stirring at 200 rpm for 24 h, surfactant modified sugar beet pulp (SMSBP) was separated from mixture
Effect of initial pH
As shown in Fig. 1a, the biosorption of RR2 on the natural biosorbent and SMSBP was significantly affected by solution pH. The maximum dye removal yields of 16.82 ± 0.43% were observed at pH 2.0 for SBP (sugar beet pulp) and 98.90 ± 0.42% at pH 3.0 for SMSBP, respectively. The good biosorption yields observed at lower pH conditions for both biosorbents can be explained by the attractive forces between dye anions and protonated biosorbent surface. The biosorption yields of the biosorbents were
Conclusion
The surfactant modification employed in this work significantly improved the biosorption potential of waste by-product of sugar beet pulp. The best batch mode decolorization conditions were determined for the modified biosorbent. Surfactant modification also reduced the required amount of biosorbent and SMSBP reached higher biosorption yields when compared unmodified one. It was noticed that the equilibrium was attained within 20 min. Dye removal process followed by the pseudo-second-order
Acknowledgements
This work was supported by the Commission of Scientific Research Projects of Eskişehir Osmangazi University (ESOGU) with the project number 201219009. The authors gratefully acknowledge for financial support by ESOGU.
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