An overview of heavy metals treatment & management for laboratory waste liquid (LWL)

Abstract

The laboratory waste liquid (LWL) is the discarded liquid after the completion of analysis and is produced from the testing laboratories including regulatory institutions, colleges, universities and research organizations. This LWL is laden with a variety of heavy metals due to the use of heavy metal salts in analysis and the treatment and safe disposal of LWL is seldom given due consideration. Thus, the management of hazardous laboratory waste liquid (HLWL) containing heavy metals is essential at the source itself. Accordingly, this article presents systematic review of three processes for heavy metals removal viz. precipitation, adsorption, and membrane separation. The review covers various factors such as heavy metal removal efficiencies & concentration ranges, optimum pH, most frequently studied methods, less studied aspects, its commercial availability, operational ease, and the potential of risk minimization with due concern to toxic heavy metals. The concentrations of heavy metals in LWL is also presented. Based on the review, activated carbon (AC) adsorption appears to be the best option for LWL having heavy metals concentration of less than 10 mg/L. The heavy metals removal efficiency of more than 95% can be achieved at an AC dose of 0.2–1 g/L. The hydroxide precipitation was found to achieve more than 95% removal efficiencies at higher heavy metals concentrations. Thus, for concentrations higher than 10 mg/L up to 3000 mg/L, the hydroxide precipitation followed by activated carbon adsorption may prove beneficial.