Abstract:
This research work investigated the utilization of reactive rice husk ash (rRHA) to partial substitutefor ordinary Portland cement (OPC) to solidify heavy metal hydroxide sludge. The rRHA wasprepared by burning rice husk at 650 ?C for 1 hour and then used to replace ordinary Portlandcement (OPC) at 0, 10, 20 and 30 wt.% Fe(OH)3 , Cr(OH)3 and Zn(OH)2 were loaded to thesolidification binder at 10 wt.% throughout the experiment. A 28-day solidified waste was tested fordurability to acid corrosion and wet/dry cycle. Experimental results showed that pHs of sulfuric,nitric, acetic and carbonic acid solutions were rapidly increased during the first 8 days of contactwith the solidified waste samples and the pHs increased at a decreasing rate after that. A change inweight and diameter of the samples contacted with acid solutions was observed to increase withincreasing the level of replacement by rRHA. It was found that the solidified waste containingZn (OH)2 was less durable to acid corrosion than that containing Fe(OH)3 and Cr(OH)3 . In addition,the weight and diameter of the samples after exposure to sulfuric and carbonic acid solutions werealtered in a different manner to acetic and nitric acid solutions. Durability to acid corrosion of thesolidified wastes was in the following order: acetic < nitric < sulfuric < carbonic acid solution. Inaddition, weight loss of the solidified waste due to wet and dry cycle was not excess the standardcriteria and the rRHA resulted in greater durability of the solidified waste against wet/dry cycle.