In recent years, numerous studies have focused on the use of biochar as a biological material for environmental remediation due to its low-cost precursor (waste), low toxicity, and diversity of active sites, along with their facile tailoring techniques. Due to its versatility, biochar has been employed as an adsorbent, catalyst (for activating hydrogen peroxide, ozone, persulfate), and photocatalyst. This review aims to provide a comprehensive overview and compare the application of biochar in water remediation. First, the biochar active sites with their functions are presented. Secondly, an overview and summary of biochar performance in treating organic pollutants in different systems is depicted. Thereafter, an evaluation on performance, removal mechanism, active sites involvement, tolerance to different pH values, stability, and reusability, and an economic analysis of implementing biochar for organic pollutants decontamination in each application is presented. Finally, potential prospects to overcome the drawbacks of each application are provided.

Herein, mixed–metal nanocomposite catalysts with various compositions (CoFe2O4/xFe2O3; x = 0, 0.25, 0.50, 0.75 and 1) were successfully fabricated by a co–precipitation method. The composition and morphology of the catalyst were systematically characterized. The catalyst with the highest Co content (CoFe2O4), exhibited the greatest efficiency for the acid orange 7 (AO7) degradation via peroxymonosulfate (PMS) activation. The effects of several experimental parameters including pH, CoFe2O4 loading, and PMS dosage on AO7 degradation were studied, and the catalytic activity was found to increase with the mentioned parameters. Moreover, CoFe2O4 displayed adequate reusability and was able to degrade AO7 for at least four consecutive cycles. In addition, the total organic carbon (TOC) removal of CoFe2O4 was determined while the catalyst stability was observed from the metal leaching in the treated solution. Furthermore, the magnetism of CoFe2O4 provides facile separation of the catalyst from the treated solution. Sulfate radicals (SO4•–) were identified as the main reactive species responsible for AO7 degradation.