Quaternized biomass as an anion exchanger for the removal of nitrate and other anions from water

Dried Chinese Reed (Miscanthus sinensis), a fast growing plant, was used as a model biomass for the development of anion exchangers using a quaternization agent, N-(3-chloro-2-hydroxypropyl)trimethylammonium chloride (CHMAC), and a cross-linking agent, epichlorohydrin. Anions studied include nitrate, phosphate, perchlorate and sulfate. Batch mode adsorption studies were conducted using aqueous solutions of anions. Detailed kinetics were studied for nitrate removal. Parameters studied included anion concentration, agitation time, adsorbent dose, and pH. Adsorption equilibrium occurred in 10 min for all the anions studied. Equilibrium adsorption data followed both Langmuir and Freundlich isotherms. The presence of phosphate, perchlorate, fluoride and sulfate lowered the adsorption significantly. The effects of pH on adsorption and desorption show that ion exchange is involved in the adsorption process. The adsorption capacity of the cross-linked and quaternized Chinese Reed for nitrate, sulfate, phosphate and perchlorate was found to be 7.55, 13.25, 16.61 and 10.07mg of anion per g of the anion exchanger, respectively. (C) 2004 Society of Chemical Industry.