Adsorption of Antimony by Bagasse Fly Ash: Chemical Modification and Adsorption Mechanism.

Modification of bagasse fly ash (BFA) and the adsorption mechanism of antimony (Sb) by modified BFA were studied. It was found that BFA grafted with acrylic acid (BFAG) and BFA treated with hydrochloric acid (BFA/HCl) led to a decrease in the pH of the zero point of charge (pHzpc) of the adsorbents. The pHzpc of BFA, BFAG, BFA/HCl and activated carbon (AC) were 8.3, 6.4, 6.2 and 8.2, respectively. The maximum adsorption capacities (Qmax) of Sb by BFA, BFAG, BFA/HCl and AC were 0.14, 0.34, 0.38 and 0.29 mg Sb/g adsorbent, respectively. Modified BFA had Qmax higher than AC although the BET surface area of AC was the highest. This was due to the system pH of BFAG and BFA/HCl was 5.20-6.00 and the pHzpc of BFAG and BFA/HCl accounted for 6.4 and 6.2, respectively. Therefore, the adsorbent surface had a positive charge, resulting in increasing adsorption of Sb.

Application of 'waste' wood-shaving bottom ash for adsorption of azo reactive dye.

The utilization of wood-shaving bottom ash (WBA) for the removal of Red Reactive 141 (RR141), an azo reactive dye, was investigated. WBA/H(2)O and WBA/H(2)SO(4) were made by treating WBA with water and 0.1M H(2)SO(4), respectively, to increase adsorption capacity. Adsorption of RR141 from reactive dye solution (RDS) and reactive dye wastewater (RDW) by WBA/H(2)O and WBA/H(2)SO(4) involved the BET surface area and pore size diameter. Properties of adsorbents, effect of contact time, initial pH of solution, dissolved metals and elution studies indicated that the decolorisation mechanism involved both chemical adsorption and precipitation with calcium ions. In addition, the WBA/H(2)SO(4) surface might contain sulphate-cation complexes that were specific to enhancing dye adsorption from RDW. The adsorption isotherm had a best fit by the Freundlich model. Freundlich parameters showed that WBA/H(2)O used more heterogeneous surface than WBA/H(2)SO(4) and activated carbon for RDW adsorption. A thermodynamic study indicated that RDW adsorption was an endothermic process. The maximum dye adsorption capacities of WBA/H(2)O, WBA/H(2)SO(4) and activated carbon obtained from a Langmuir model at 30 degrees C were 24.3, 29.9, and 41.5mgl(-1), respectively. In addition, WBA/H(2)O and WBA/H(2)SO(4) could reduce colour and high chemical oxygen demand (COD) of real textile wastewater. According to the difficulty in the elution study, it was an environmentally safe disposal of this waste. Therefore, WBA, a waste from combustion of wood shavings, was suitable to be used as an effective adsorbent for azo reactive dye removal.