Non-demineralized paper waste sludge derived magnetic biochar as sorbs for removal of methylene blue, phosphorus, and selenate in wastewater

Pollution has continued to be the source of elevated nutrient levels in catchment areas, causing eutrophic conditions that threaten human health. Adsorption has been seen as a cost-effective and simple process of removing and recovering nutrients from wastewater. Biomass feedstocks have received significant research interest in recent years on the production of biochar and its magnetized variants for wastewater treatment. However, there have been minimal studies on the use of paper waste sludge obtained from the recycling industry as a feedstock for biochar production used in wastewater treatment. Hence this study focused on the production of magnetic biochar composites as an adsorbent for nutrient removal and recovery from wastewater. Neat non-demineralized biochar and its magnetized variant were produced using paper waste sludge through co-pyrolysis at 450 °C and for the magnetized variant, the feedstock was synthesized using Fe³⁺ and Fe²⁺ salts. The biochar produced exhibited good structural and chemical properties suitable for adsorption. Hence further analysis was performed using MBC-SPS-450 for the removal of phosphorus (P), selenate (Se), and methylene blue (MB) from wastewater. The observed efficiencies for P, Se, and MB were 48.83, 58.43, and 5.92 mg g ^− 1 respectively. From the results obtained, the magnetized variant (MBC-SPS-450) displayed excellent adsorption efficiencies, lower loading requirements with an optimum loading of 5 g L ^− 1, easy removal from solution by magnets, and was regenerated with excellent adsorption efficiencies. These excellent results position paper waste sludge-derived biochar as a good and low-cost adsorbent for the removal and recovery of nutrients from wastewater with the added benefit that it is part of the recycling process.