A new adsorption process for As(V) ion removal from an aqueous solution was studied using molybdate-based chitosan gel beads. Arsenate ions were strongly adsorbed in the pH range from 2.5 to 3.5 with a minimum release of molybdate ions. The sorption mechanism assumed here is a complexation between arsenate ions and molybdate ions. Even at low equilibrium concentration, the sorption capacity is high, and allows the process to be used as a polishing treatment. Phosphates ions significantly depress arsenate collection because of a competing reaction for the active sites. Simultaneously with the arsenate sorption, molybdenum is released to a significant extent (about 15-20 percent). However this molybdenum release can be reduced using an orthophosphoric pre-treatment of MICB, which allows the weakly bound molybdenum to be removed from the sorbent and therefore its release does not exceed 2 percent. A binding constant of 1.2 L mg~(-1) and a capacity constant of 197.6 mgAs g~(-1)Mo were obtained, using the Langmuir model. A selective and total elution can be carried out using a 0.1 mol L~(-1) orthophosphoric acid solution. The spent sorbent can be re-used for further sorption of arsenate ions with the same performance. The process has been successfiilly carried out with real industrial effluents from Mining and Microelectronics.
展开▼
