Mechanism of biosorption of metals from e-waste by microscopic algae

Abstract

The development of technologies for extracting metals from waste is an urgent task. In this study, a poorly studied technology for the extraction of metals from electronic waste by microscopic algae, based on the biosorption method, was considered. The efficiency of the technology is determined both by the parameters of the biosorption process (properties and dose of biomass, temperature, pH, contact time of the adsorbate with the biosorbent), and the chemical composition of the solution obtained during the leaching of prepared electronic waste and containing metals. In the course of the study, the presence of functional groups in the biosorbent that could enter into chemical interaction with the recovered metals, the chemical properties of metals in the test solution were identified, and the leaching of the sorbed metals from the biosorbent was assessed. Microscopic algae of the species Chlorella sorokiniana, Chlorella vulgaris, Chlorella spirulina, and the genus Scenedesmus sp. were used as a biosorbent. The metal was sourced from mobile phone/smartphone screens and computer monitors. Analysis of the component composition of screens and monitors showed that it is represented by more than 10 different metals belonging to the group of basic metals and 7 metals belonging to the group of rare earth, rare and precious metals. Using the method of IR spectroscopy, the presence of the following functional groups in the cell walls and organoids of microscopic algae was proved: amino groups, hydroxyl and carboxyl groups. The results of experimental studies have established a mixed mechanism of biosorption, including physical sorption and chemisorption. As evidence, we used data on the partial leaching of sorbed metals from microscopic algae after the completion of the process.