Optimizing Fly Ash and Cement Ratios for Immobilizing Lead and Arsenic in Liquid Hazardous Waste

Abstract

Improper handling of hazardous and toxic industrial wastes can directly impact human health and the environment. To overcome this problem, the PT Prasadha Pamunah Limbah Industri (PPLI) provides industrial waste processing services including Stabilization and Solidification (S/S) treatment using cement and fly ash mixtures. This research evaluated the efficiency of S/S in reducing the heavy metal content of lead (Pb) and arsenic (As) in liquid hazardous waste, using waste, fly ash, and cement ratios of 1:1:1, 1.5:1:0.5, and 2:0.5:0.5, tested with the Toxicity Characteristic Leaching Procedure (TCLP). The results demonstrated that the 1:1:1 and 1.5:1:0.5 ratios effectively reduced the Pb and As content, achieving reduction efficiencies of 99.50% and 99.34% for the 1:1:1 ratio, and 99.36% and 99.19% for the 1.5:1:0.5 ratio, respectively. However, the 2:0.5:0.5 ratio produced a brittle mixture prone to leachate formation and it is not recommended. According to the TCLP results, the 1:1:1 and 1.5:1:0.5 ratios met the environmental quality standards outlined in Government Regulation No. 22 of 2021 on Environmental Protection and Management. The statistical analysis using an independent T-test indicated no significant difference in the reduction efficiency between the two effective ratios, suggesting that either can be reliably used. This study addresses existing research gaps by applying the S/S method to liquid hazardous waste, an area previously focused on soil applications. Besides, it demonstrates that high immobilization rates exceeding 99% can also be achieved for Pb and As using cement and fly ash. This study provides a novel perspective on S/S applications, enhancing the efficiency and applicability of hazardous waste treatment processes.