Advanced Separation Processes for Recovery of Critical Raw Materials From Renewable and Waste Resources

Abstract

In the present world, raw materials are in greater demand but are becoming ever scarcer. To imply the sign of criticality, knowing that there is a high risk of supply shortage and economic impact, the European Commission formally adopted a list of specific raw materials designated as 'critical raw materials' (CRMs) as represented in Fig. 1. Regulatory policies are being implemented to bring down the extraction/mining trend for ultimately extending the lifetime of CRMs. On the other hand, advanced recycling systems are being practiced to promote and establish a core circular economy context by recycling, recovering, and separating CRMs. These recycling approaches are mostly aimed at the recovery of various metals such as palladium, gallium, germanium, copper, which are critical raw materials for the technology sector. There are also a specific group of CRMs including Phosphorus (P), natural phosphate rock and Magnesium (Mg) representing major primary, and secondary resources for industrial applications of high economic value (Loganathan et al., 2017; Yan et al., 2018). Crucially only P and Mg are deemed suitable candidate CRM's for recovery from waste streams through effective separation and recycling strategies. Further, its supply-demand status and substitutability risks have driven the requisites for resource supplementing technology through effective recovery and recycling strategies.

Use of wastewater alum-coagulation sludge as a phosphorus fertiliser – a mini review

“…The remaining P ore reserves are expected to have lower total or soluble P concentrations, increased impurities (such as clay), greater difficulty in physical accessibility, higher waste generation per tonne of extracted P, and consequently, elevated input and extraction costs (Cordell and White 2014 ). Rameshkumar et al ( 2020 ) express concerns that the rate of P extraction far exceeds regeneration, estimating its depletion within the next 40–100 years.…”

“…(3) To propose effective methods for addressing constraints associated with the utilization of Al sludge on agricultural lands. While existing literature includes comprehensive reviews on the use of P recovered through adsorption (Luo et al 2023 ; Zheng et al 2023 ) and membrane processes (Li et al 2021 ; Rameshkumar et al 2020 ), there is currently a notable absence of a comprehensive review specifically addressing P recovery by coagulation using Al salts for use as fertilizer. This paper aims to bridge this knowledge gap by presenting a review that sheds light on the beneficial utilization of substantial quantities of Al-sludge generated in water treatment plants globally.…”