Valorization of brewery wastewater sludge for phosphate removal: preparation, optimization, and performance of chemically activated carbon

Abstrakt

Phosphate discharge from industrial effluents, including brewery wastewater, contributes significantly to eutrophication and the degradation of aquatic ecosystems. The development of sustainable and low-cost materials for phosphate removal is therefore essential.

This study evaluates activated carbon produced from wastewater treatment sludge generated at Dashen Brewery (Gondar, Ethiopia) for phosphate removal from aqueous solutions. The sludge was chemically activated using phosphoric acid (H₃PO₄) and sodium hydroxide (NaOH), followed by thermal carbonization. Physicochemical characterization was performed using Brunauer–Emmett–Teller (BET) surface area analysis, Fourier transform infrared (FTIR) spectroscopy, point of zero charge (pHPZC), and proximate analysis. The H₃PO₄-activated carbon exhibited a well-developed porous structure with a surface area of 427.05 m²/g and showed higher phosphate removal efficiency than the NaOH-activated samples. Optimization using response surface methodology (RSM-CCD) identified optimal conditions at pH 3, a contact time of 120 min, and an adsorbent dosage of 2.61 g/L, achieving 80.3% phosphate removal and an adsorption capacity of 13.6 mg/g. Adsorption kinetics followed a pseudo-second-order model, indicating chemisorption. Regeneration tests showed that the adsorbent retained over 50% of its initial efficiency after three cycles. The results demonstrate that brewery sludge can be effectively valorized into an efficient adsorbent for phosphate removal, with potential applicability to similar sludge streams from other breweries.