Industrial steel waste-based adsorbent: An effective phosphate removal from aqueous media

Abstract

This work offers the alternative to mitigate the problem of eutrophication of water bodies that can result in a serious threat to environment and aquatic life by using steel wastes for phosphate removal. Produced on the scale of thousands of tons per year, these wastes can contribute to air, soil, and water pollution when discharged without a proper management. In this context, this work evaluates the potential of phosphate remediation by adsorption applying steel industry wastes, addressing two important environmental problems at once. For the first time, blast furnace sludge (BFS) and the powder from Kanbara reactor (KR) without pre-treatment were used for the elucidation of the removal mechanism of phosphate, employing the method of sequential extractions, kinetic studies, and thermodynamics. The chemical and structural analyses demonstrated the materials present an irregular morphology with most of the pores in the mesopore range being mainly composed by alkali metals and metal oxides. Although approximately 99% of phosphate removal efficiency was reached for both wastes in 24 h, the speciation studies showed phosphate and KR interacts too strongly making its reuse hardly feasible and therefore not suitable from a practical point of view. For BFS, on the contrary, the thermodynamic data indicated a physisorption process offering the advantage of reutilization. In addition, about 97% of phosphate removal is achieved during the first 10 min of adsorption, regardless the solution pH, thus offering good prospects in aggregating value to steel industry wastes as adsorbents being in line with a sustainable economy.