UiO-66-NH2/chitosan with microalgae platform for gold valorization from waste microelectronics

Abstract

The combination of UiO-66-NH2/chitosan (CTS) and microalgae was effective in precious metal recovery of electronic wastes (E-wastes) from discarded microchips. Herein, zirconium-based metal-organic frameworks were introduced to bind metal ions from the E-waste. Thus, UiO-66-NH2 was linked to CTS as examined by Fourier-transform infrared spectroscopy (FT-IR). Au(III) leachate solutions were prepared via acidic treatments from the microcomputer chips that were used to test metal binding using UV-Vis absorption spectroscopy. The prepared UiO-66-NH2/CTS was tested to recover Au(III) ions from the liquid phase waste, which exhibited higher adsorption capacity than UiO-66, UiO-66-CTS, and UiO-66-NH2. The inclusion of microalgae in UiO-66-NH2/CTS system enhanced gold adsorption efficiency and binding of Au(III) ions onto UiO-66-NH2/CTS and UiO-66-NH2/ CTS/microalgae attained equilibrium within a few hours. UiO-66-NH2/CTS showed an adsorption capacity of 576 mg/g, which increased to - 671 mg/g after the introduction of microalgae of Spirulina maxima. The pH effect on Au(III) binding revealed that electrostatic interactions between the negatively charged UiO-66 particles and gold anions decreased the adsorption capacities at higher pH values. The findings highlighted the potential use of UiO-66-NH2/CTS and microalgae for effective gold recovery from the E-waste.