Two-stage sustainable approach for tin recovery from waste PCBs using Acidithiobacillus ferrooxidans leaching and bentonite clay adsorption

Abstract

Tin (Sn), a precious metal widely used for corrosion resistance applications in several industries, which was present 42.40 weight % in the unused printed circuit boards (PCBs). This waste globally affects the environment. Therefore, this research emphasizes on tin recovery by two stage operations like Leaching by Acidithiobacillus ferrooxidans and adsorption by Bentonite clay) with the help of RSM technique. This study has been achieved 97.33% tin recovery with a desirability rate of 0.845 under optimized parameters such as temperature 29°C, PCBs sample size 0.25 μm, pulp density 22.06 g/L and time 28 days. Optimized values applied the experimental bacterial leaching and achieved 97.7% of tin recovery efficiency and optimized parameters (leaching duration of 21 days, a pulp density of 15 g/L, a particle size of 0.25 μm and a temperature of 20°C). After bacterial leaching, study is continued adsorption with clay (Bent) for reclaiming the tin (Sn²⁺) from bio-leachate solution which was recovered 97.86% under optimized parameters (temperature - 80℃, Adsorbent dosage – 4 g, Bent size - 0.05 mm and time – 4 h). However, choosing this toxic free bacterial leaching and bent clay adsorption techniques could promote tin recycle without affecting the environment.