Experimental Study on the Elimination of Colour and Organic Matter from Wastewater Using an Inexpensive Biomaterial, Chitosan

Abstract

Chitosan has been investigated as an inexpensive, biologically derived adsorbent and/or primary coagulant for two reactive azo dyes in textile wastewater. At natural pH, complete elimination of colour was achieved from 0.1 g/L aqueous solutions of the textile dyes Procion Orange MX-2R and Procion Red MX-5B with a dose of 6 g of chitosan per litre of dye solution. However, when pH was lowered (to 4.8 and 5.5 respectively), a dose of only 1 g of chitosan per litre was necessary to eliminate colour and drastically reduce TOC (total organic carbon) and chemical oxygen demand for the same concentration of dyes. This allowed about an 80% reduction in sludge volume production. Addition of sodium phosphate dibasic and potassium sulfate improved the dye removal at higher pH. Colour removal decreased significantly with or without added salts as pH was adjusted above 7. Equilibrium adsorption experiments showed that both dye solutions follow the Freundlich isotherm, but not the Langmuir isotherm. Kinetics measurements show a better fit to the pseudosecond-order Lagergren model than to the first-order Lagergren model. Brunauer-Emmett-Teller, or BET, surface area analysis and scanning electron microscope micrographs were included for better understanding of the nature of the chitosan surface with and without adsorbed dye. Chitosan appears to be a natural, clean and excellent product for the adsorption of Procion Orange MX-2R and Procion Red MX-5B in mildly acidic conditions.

Adsorption Characteristics of Reactive Black 5 from Aqueous Solution onto Chitosan

“…This is the most abundant biopolymer in nature after cellulose. The high proportions of amino functions in chitosan have been found to provide novel adsorption properties for many metal ions [25][26][27] and organic dyes [28][29][30][31][32][33][34][35][36][37].…”

Adsorption of Methyl Orange onto Chitosan from Aqueous Solution

“…This is the most abundant biopolymer in nature after cellulose. The high proportions of amino functions in chitosan have been found to provide novel adsorption properties for many metal ions [25][26][27] and organic dyes [28][29][30][31][32][33][34][35][36]. The deacetylated amino groups in chitosan can be protonated and the polycationic properties of the polymer are expected to contribute to the charged interactions with a model dye, methyl orange (MO), which is an anionic azo dye (Figure 1(b)).…”

Adsorption of remazol red RR onto chitosan from aqueous solution

“…This is the most abundant biopolymer in nature after cellulose. The high proportions of amino functions in chitosan have been found to provide novel adsorption properties for many metal ions (Chu 2002;Rangel-Mendez et al 2009) and organic dyes (Modak et al 2009;Lazaridis et al 2007;Chiou and Li 2002). The deacetylated amino groups in chitosan can be protonated and the polycationic properties of the polymer are expected to contribute to the charged interactions with a model dye, remazol red RR (RRR), which is an anionic azo dye (Fig.…”