Sustainable safe and environmentally friendly process to recovery valuable materials from hazardous waste InP

• ‘VD-DC’ was proposed for recovering In and P from InP waste for the first time. • The feasibility of this new process was verified by calculation and experiments. • The optimal conditions were P = 30 Pa, t = 3.5 h, and T = 1123 K (573 K for DC). • Phosphorus was recovered in a non-toxic and stable form. • This process which avoids toxicity, pollution has potential in real applications. With the rapid expansion of the market scale for indium phosphide (InP) semiconductors in high-tech industries such as optoelectronics and solar energy, the generation of hazardous waste InP has also increased dramatically, and the task of recycling waste InP is urgent. However, InP as a representative phosphide semiconductor is prone to produce highly toxic substances such as yellow phosphorus and PH 3 in the recycling process, which discourages most companies from using it. In this study, a safe and efficient method of “vacuum decomposition-directional condensation (VD-DC)” is proposed to recover valuable materials from waste InP. In this method, briquetting pretreatment is used to improve thermal conductivity. At a decomposition temperature of 1123 K, system pressure of 30 Pa, and holding time of 3.5 h, indium with a purity of 99.43 wt% is obtained, and the direct yield reaches 98.54%. Non-toxic and stable red phosphorus with a purity of 98.14 wt% is recovered by converting the condensed yellow phosphorus at 573 K. Vacuum technology significantly reduces the decomposition temperature of InP and avoids the emission of waste water and waste gas, thus operating in an environmentally friendly manner.