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Phosphate removal from water by res mud using crossflow microfiltration

Tài liệu tham khảo chuyên ngành môi trường, ứng dụng của bùn đỏ. | Pergamon Wat. Res. Vol. 32 No. 3 pp. 717-726 1998 1998 Elsevier Science Ltd. All rights reserved __ Printed in Great Britain PII S0043-1354 97 00236-4 0043-1354 98 19.00 0.00 PHOSPHATE REMOVAL FROM WATER BY RED MUD USING CROSSFLOW MICROFILTRATION G. AKAY1 B. KESKINLER2 A. CAKICI2 and u. DANIS2 Department of Chemical Engineering University of Nottingham Nottingham NG7 2RD U.K. and 2Faculty of Engineering Ataturk University 25240 Erzurum Turkey First received October 1996 accepted in revised form June 1997 Abstract Red mud which is a waste material formed during the production of alumina and primarily contains ferric and aluminium oxides was used as an adsorbent for the removal of phosphate ions from water using crossflow microfiltration. It is shown that phosphate ions act as a coagulant for red mud particles forming a compressible cake with a compressibility index of unity. As shown also by dead-end filtration experiments the cake resistance decreases with increasing phosphate concentration. The phosphate rejection is a strong function of feed dispersion pH phosphate and red mud concentration ratio as well as the concentration of co-ions such as sulphate ions used to adjust the dispersion pH. Under certain conditions especially when pH 5.2 steady state permeate flux and phosphate rejection reach a maximum with 100 rejection achievable. The permeate also contain metal ion impurities originating from red mud and their concentrations increase with increasing red mud concentration and decreasing pH. The effects of other process variables crossflow velocity and membrane pore size on phosphate rejection and permeate flux are also studied. 1998 Elsevier Science Ltd. All rights reserved NOMENCLATURE C r c Transient and steady state phosphate concentrations in permeate mM CpF Phosphate concentration in the feed mM Crf Red mud concentration in the feed g 1 43 Volume average particle size zm z 32 Surface average particle size zm d- Membrane pore size m