Biochar/layered double hydroxides composites as catalysts for treatment of organic wastewater by advanced oxidation processes: A review

Heterogeneous advanced oxidation process has been widely studied as an effective method for removing organic pollutants in wastewater, but the development of efficient catalysts is still challenging. This review summaries the present status of researches on biochar/layered double hydroxides composites (BLDHCs) as catalysts for treatment of organic wastewater. The synthesis methods of layered double hydroxides, the characterizations of BLDHCs, the impacts of process factors influencing catalytic performance, and research advances in various advanced oxidation processes are discussed in this work. The integration of layered double hydroxides and biochar provides synthetic effects for improving pollutant removal. The enhanced pollutant degradation in heterogeneous Fenton, sulfate radical-based, sono-assisted, and photo-assisted processes using BLDHCs have been verified. Pollutant degradation in heterogeneous advanced oxidation processes using BLDHCs is influenced by process factors such as catalyst dosage, oxidant addition, solution pH, reaction time, temperature, and coexisting substances. BLDHCs are promising catalysts due to the unique features including easy preparation, distinct structure, adjustable metal ions, and high stability. Currently, catalytic degradation of organic pollutants using BLDHCs is still in its infancy. More researches should be conducted on the controllable synthesis of BLDHCs, the in-depth understanding of catalytic mechanism, the improvement of catalytic performance, and large-scale application of treating real wastewater.

Automated summary

This review discusses the current research status of biochar/layered double hydroxides composites (BLDHCs) as catalysts for the treatment of organic wastewater. The synthesis methods of layered double hydroxides, characterizations of BLDHCs, impacts of process factors on catalytic performance, and advances in various advanced oxidation processes are summarized. The integration of layered double hydroxides and biochar shows synergistic effects in improving pollutant removal. BLDHCs have been proven to enhance pollutant degradation in heterogeneous Fenton, sulfate radical-based, sono-assisted, and photo-assisted processes. The catalytic degradation of organic pollutants using BLDHCs is still in its early stages and further research is needed to investigate controllable synthesis, catalytic mechanism, improved performance, and large-scale application.