Preparation of xylan citrate--a potential adsorbent for industrial wastewater treatment.

The novel and degradable xylan citrate was prepared by the environmental-friendly semi-dry oven method. Xylan reacted with citric acid (CA) to yield xylan citrate at high temperature. The influence of the different weight ratios of CA and xylan on the product yield, the carboxyl group content and degree of esterification were comparatively discussed. The results showed that there were higher carboxyl group content and degree of esterification in modified xylan than native xylan. The product yield of 128.2%, the carboxyl group content of 1174.3 meq/100 g and degree of esterification of 33.1% were achieved at the CA/xylan weight ratio of 2.4 in the absence of catalyst. Furthermore, the adsorption capacity of xylan after modification was improved greatly. These materials with better properties can enhance their water affinity, and improve their adsorption of copper ions and methyl orange in aqueous solution due to carboxyl groups.