H3PO4-activated sawdust and rice husk as effective decolorizers for textile wastewater containing Reactive Black 5

摘要

Textile wastewater contains significant amounts of dyes and chemicals, which makes it very difficult to be treated. Reactive Black 5 is one of the most widely used azo dyes that cause severe impact on environment and aquatic life. Activated carbons are known for their high adsorption capacities, and the objective of the current study was to prepare an effective low-cost adsorbent. H3PO4 acid-activated sawdust and rice husk which were prepared using a simple and low-cost method successfully adsorbed Reactive Black 5 (RB 5) in hypersaline synthetic and real textile dye bath wastewaters. SEM analysis of activated carbon made from these two materials showed an enhanced pore structure. 0.10 g of activated sawdust carbon decolorized 88, 97 and 75% of neat RB 5 solution, synthetic textile wastewater and real textile dye bath wastewater, respectively. RB 5 adsorption is pH dependent, and low pH facilitates the dye adsorption. Langmuir and Freundlich isotherm models were used to analyze the equilibrium adsorption data, and only the Langmuir isotherm model shows a good correlation (R-2=0.99). Kinetic data match well with the pseudo-second-order model, and the calculated rate constants are 6.09x10(-3) g mg(-1) min(-1) and 9.88x10(-3) g mg(-1) min(-1) for activated carbon of sawdust and rice husk, respectively. Thermodynamic parameters, Delta G(0), Delta H-0 and Delta S-0, for both types of activated carbon show that the adsorption process is favorable, endothermic and spontaneous.