Bioleaching of critical metals from waste OLED touch screens using adapted acidophilic bacteria

Abstract

The mobile phone is a fast-growing E-waste stream that includes hazardous substances and valuable metals. Smartphone touch screens (SPTS) contain a considerable amount of critical metals, such as indium and strontium that can be recovered from end of life devices as a secondary resource. Bioleaching is an emerging and environmentally friendly method for metal recovery from electronic waste. In the present study, bioleaching was assessed for the extraction of indium and strontium from organic light emitting diode type smartphone touch screens. A statistical approach based on the response surface methodology was successfully applied. The effects of influential variables: pH, ferrous sulfate, elemental sulfur, and solid content and their interactions on indium and strontium recovery using adapted Acidithiobacillus ferrooxidans were evaluated. Under optimum conditions (ferrous sulfate: 13.0 g/L; solid content; 3.0 g/L; elemental sulfur: 5.6 g/L; and initial pH of 1.1), a complete indium extraction was observed, with a concentration in solution of about 200 mg/L indium. As concerns strontium, a 5% extraction efficiency was observed, which, even if quite low, resulted in a relatively high strontium concentration in solution, around 3000 mg/L, due to its high content in the solid (2%). This work opens new perspectives in the application of clean technologies for the extraction of valuable metals, such as indium and strontium from smartphone screens.

The Extraction and Separation of Scarce Critical Metals: A Review of Gallium, Indium and Germanium Extraction and Separation from Solid Wastes

“…In recent years, researchers have attempted to carry out the bioleaching of indium from waste LCDs, such as sulfur-oxidizing bacteria [66], acidophilic iron-oxidizing bacteria [67], Aspergillus niger fermentation broth [68], Eleocharis acacularis [69], etc. In addition, different bioleaching approaches (as shown in Figure 7a) have an impact on the leaching efficiency of indium [70].…”

A comprehensive review of bioleaching optimization by statistical approaches: recycling mechanisms, factors affecting, challenges, and sustainability

“…At optimal conditions of ferrous sulfate: 13.0 g L −1 , pulp density 3 g L −1 , initial sulfur concentration 5.6 (g L −1 ), and initial pH 1.1, In was recovered completely, but Sr was not appropriately recovered (only 5%). 92 In another investigation, Arshadi et al (2020) studied the RSM-optimized extraction of Cu and Ni from disposed of computer-printed circuit boards (CPCBs) utilizing Aspergillus niger. Optimization for maximizing the percentage of Cu and Ni recovery was done with pH of 5.15, pulp density of 10 g L −1 , 1 × 10 7 spores of fungi, and 4.5 days for the time the powder was added, resulting in 97% of Cu and 74% of Ni.…”

“…At optimal conditions of ferrous sulfate: 13.0 g L −1 , pulp density 3 g L −1 , initial sulfur concentration 5.6 (g L −1 ), and initial pH 1.1, In was recovered completely, but Sr was not appropriately recovered (only 5%). 92 …”