Co-pyrolysis of microalgae and sewage sludge over ZnO/MgO/CeO2/HZSM-5 catalyst for energy and water treatment application

The growing demand for sustainable energy and efficient waste management has fueled demand in producing bioenergy from biomass. This study delves into the co-pyrolysis of microalgae and sewage sludge using a novel ZnO/MgO/CeO 2 /HZSM-5 catalyst, aiming to enhance biofuel production and contribute to environmental remediation through water treatment applications. The metal oxides loaded HZSM-5 hybrid catalyst was prepared by applying the impregnation technique for incipient wetness. The synthesized catalyst was characterized using different analytical techniques. The co-pyrolysis process was conducted at a temperature of 500 °C, biomass blend ratio of 1:1 and biomass to catalyst ratio of 2:1. The findings established that the co-pyrolysis of microalgae and sewage sludge using ZnO/MgO/CeO 2 /HZSM-5 catalyst significantly enhanced the production quality of bio-oil relative to the pyrolysis of individual feedstocks. Benzene and its derivatives are the predominant aromatic compounds present in the pyrolytic bio-oils. The removal efficiency of methylene blue (MB) from an aqueous solution onto biochar obtained from the co-pyrolysis of microalgae and sewage sludge modified with catalyst (CMS biochar) was assessed through batch adsorption experiments. The optimum MB dye removal (93.2 %) was obtained using a 50 minute contact time, a 60 mg/L initial MB dye concentration, and a 40 mg CMS biochar dosage. The biochar demonstrated strong potential for reuse, with only a slight decline of approximately 5 % in its removal efficiency after six regeneration cycles. This study highlights the dual benefits of the co-pyrolysis process, demonstrating its viability not only for bioenergy generation but also for addressing water treatment challenges. The findings offer new perspectives on the application of advanced catalytic systems in biomass conversion, offering a sustainable approach to managing waste and producing valuable resources. • Pyrolysis of microalgae alone exhibited highest conversion rate of 62.2 %. • Benzene and its derivatives are the predominant aromatic compounds in the bio-oils. • Optimum methylene blue (MB) dye removal of 93.2 % was achieved using CMS biochar. • CMS biochar showed a slight decrease of ∼5 % in removal efficiency after six reuse cycles.