Optimising the preparation of activated carbon from digested sewage sludgeand coconut husk

Preparation of activated carbon from sewage sludge is a promising way to di spose of sewage sludge as well as to produce a low-cost adsorbent for pollu tant removal. This research work aimed to optimise the condition for activa ted carbon preparation from anaerobically digested sewage sludge with the a dditive coconut husk. The sewage sludge sample was mixed with the additive coconut husk. The preparation condition variables investigated involved the concentration of the ZnCl2 solutions, heating temperature, dwell time and heating rate in pyrolysis and the mixing ratio of coconut husk to sewage sl udge. Surface area, pore size distribution, aqueous phenol adsorption capac ity and the production yield of the final products were determined and comp ared. Experimental results revealed that low concentrations of ZnCl2 soluti on tended to improve the microporosity of the final product. Heating temper ature had a considerable impact on the surface area, pore size distribution and phenol adsorption capacity of the final products, whereas dwell time a nd heating rate performed comparatively insignificantly. The effect of incr easing the mixing ratio of coconut husk to sewage sludge was principally to increase the microporosity of the final products. The activated carbon wit h the highest BET surface area was produced with the activation of 5 M ZnCl 2 solution and, thereafter, pyrolysis at a heating temperature of 500 degre esC for 2 h with a heating rate of 10 degreesC/min, The mixing ratio of 1:4 in terms of coconut husk to sewage sludge based on their dried weights was found to be most cost effective. (C) 2001 Elsevier Science Ltd. All rights reserved.