Ammoniacal nitrogen removal from water by treatment with clays and zeolites

The objective of the present study was to investigate the removal of nitrog en in the form of ammonium ions (N-NH4+) from aqueous solutions using natur al clay and zeolite. The Croatian zeolite clinoptilolite from the area of D onje Jesenje and Croatian bentonite clay from the Kutina area were used as natural filtration materials. Alkaline and acid modification of natural cla y was performed. The N-NH4+ removal efficiency by clays in a dry state as w ell as in a liquid colloidal state have been investigated. The highest remo val efficiency value for N-NH4+ (61.1 wt%) was achieved with the natural ze olite at the lowest used initial concentration, i.e. at a concentration of 100 mg N-NH4+/l. With the increase of the initial concentration of ammoniac al nitrogen, the removal efficiency quickly decreases. This is expected as zeolites and clays have limited sorption capacities. The practical aspect i s important since an ammoniacal nitrogen elimination of more than 60.0 wt% for water containing less than 100 mg N-NH4/l can be achieved. The ammoniac al nitrogen removal efficiency is higher for clays in a liquid colloidal st ate compared to the clays in a dry state. It has been found that the acid m odification of the clay decreases the efficiency of ammoniacal nitrogen rem oval. (C) 2000 Elsevier Science Ltd. All rights reserved.