In situ carbon recovery from refractory organics in wastewater: a critical review

Abstract

Industrial wastewater containing refractory organic pollutants poses serious ecological and public health risks. Conventional mineralization technologies face challenges of carbon emissions and inefficient carbon utilization. Emerging in situ carbon recovery systems enable synchronous oxidation of organics and reduction of endogenous CO₂ into value-added products (e.g., CO, CH₃OH and C₂H₅OH). This review systematically analyses the main technologies, related mechanisms and potential enhancement pathways: photocatalysis, electrocatalysis–advanced oxidation processes (AOPs), photo-electrocatalysis, and piezocatalysis–AOPs. The comprehensive performance is quantitatively evaluated through economic analysis and life cycle assessment (LCA) methodologies. Photocatalytic technology demonstrates suitability for low-concentration wastewater treatment, though its efficiency under anoxic conditions requires further enhancement. Electrocatalysis and piezocatalysis–AOP systems exhibit superior performance in wastewater remediation with high-concentration contaminants but encounter substantial barriers including elevated operational costs and carbon footprints. Dual economic–environmental dimension analysis reveals that photocatalysis holds remarkable advantages. Whereas piezocatalysis–AOP coupling technology necessitates optimization of mechanical energy harvesting to improve economic and environmental benefits. Electrocatalysis–AOP coupling technology urgently requires the development of non-noble metal catalysts and process intensification strategies. Finally, scaling up the systems is hindered by complex water matrix interference, inefficient product separation, and inadequate reactor design. This review introduces a novel analytical framework that enables the first quantitative comparison of four in situ carbon recovery technologies through the synergistic integration of techno-economic assessment with LCA. By explicitly bridging mechanistic understanding, sustainability performance and scalability constraints, this review establishes a coherent development pathway for green chemistry applications in carbon resource recovery, offering guidance for technology selection and process optimization.