Sorption of trace elements on xylain: An experimental study

Sorption and desorption of Sr, Mn, Co, Ni, Cu, and Zn on xylain from lignites of the Mariza-East coal basin (Bulgaria) were studied. Sorption behaviour for all the studied elements was found to be of similar pH dependence for all elements. The maximum quantities bound vary from 0.104 meq (Sr) to 0.167 meq for Cu. On treatment with a complex-forming agent such as tartaric acid, a high degree of extraction was achieved. However, appreciable amounts of elements remain tightly bound on the sorbent. When present simultaneously in solution, the quantity of every element sorbed, excluding Cu, is lower as compared with the quantities from the experiments for single cations. The cation-exchange mechanism of the sorption and formation of covalent links was determined. Such processes may be responsible for part of the organically-associated elements in coals in case they are influenced by solutions enriched in some trace elements.