AUTHOR=Suiyi Zhu , Jian Wang , Yuhong Huang , Ying Wang , Yuxin Zhang , Jiabao Qin , Jiancong Liu , Jinlu Yao , Meichun Ji TITLE=Perspective on pH adjustment in hydrometallurgical recycling of valuable metals from waste JOURNAL=Frontiers in Chemistry VOLUME=11 YEAR=2023 URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2023.1177173 DOI=10.3389/fchem.2023.1177173 ISSN=2296-2646 ABSTRACT=

pH adjustment was considered a simple step in the hydrometallurgy process, but its complicated operation was ignored in the past. In some industrial applications, the leachate pH was slowly adjusted by a diluted alkaline solution, with the defects of doubling the leachate volume and causing droplet hydrolysis/coagulation. Up to date, promising routes have been developed for rapid pH adjustment, especially in sealed high-temperature/pressure vessels. New routes emerged in some redox/decomposition reactions of nitrate/urea and organics. Such reactions did not start and/or were slow at room temperature but started spontaneously at high temperatures to generate/consume free H+. This induced pH adjustment in a rapid and homogeneous way.