Sustainable Adsorption of Rhodamine B and Heavy Metals Using Sewage Sludge-Derived Biochar
Kanafin Y.N. Mukhametrakhimova A. Turpanova R. Poulopoulos S.G.
January 2026Multidisciplinary Digital Publishing Institute (MDPI)
ChemEngineering
2026#10Issue 1
The sustainable management of sewage sludge remains a key environmental challenge for rapidly urbanizing regions such as Kazakhstan. This study explores the potential of sewage sludge-derived biochar as an efficient, low-cost adsorbent for removing Rhodamine B (RhB) dye and toxic metals from water. Sewage sludge was pyrolyzed at 700 °C (BC) and subsequently activated with hydrochloric acid (BCH) and sodium hydroxide (BCN) to improve its surface functionality and porosity. The morphology, surface area, porosity, and functional groups of the obtained biochars were characterized using SEM-EDS, BET, FTIR, and XRD analyses. Batch adsorption experiments demonstrated that the pseudo-second-order kinetic model (R2 = 0.99) best described the data, indicating chemisorption-controlled uptake. Experimental RhB adsorption capacity was 14.53 mg/g for BCH at RhB concentration of 75 mg/L after 120 min. Moreover, BCH exhibited enhanced metal adsorption capacities of 22.85 mg/g (Cu2+), 17.55 mg/g (Zn2+), 15.08 mg/g (Cd2+), 7.97 mg/g (Cr3+), and 3.68 mg/g (As3+). These results confirm that acid activation significantly improves adsorption efficiency compared with pristine biochar due to increased surface area and the introduction of oxygen-containing functional groups. Overall, sewage sludge-derived biochar shows strong potential as a sustainable adsorbent for dye and heavy metal removal.
biochar , heavy metals , municipal sewage sludge , pyrolysis , rhodamine B
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Faculty of Natural Sciences, L.N. Gumilyov, Eurasian National University, Astana, 010000, Kazakhstan
School of Intelligent Systems, Astana IT University, Astana, 010000, Kazakhstan
Department of Chemical and Materials Engineering, School of Engineering and Digital Sciences, Nazarbayev University, Astana, 010000, Kazakhstan
Faculty of Natural Sciences
School of Intelligent Systems
Department of Chemical and Materials Engineering
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Книга Публикация научной статьи Волощук 2026 Book Publication of a scientific article 2026