Preparation and Adsorption Performance of Composite Activated Carbon from Organic Sludge and Biomass

Organic/inorganic separation pretreatment of sewage sludge (SS) can enrich carbon resources in SS into organic sludge (OS), thereby facilitating the preparation of activated carbon (AC). Herein, three composite ACs were synthesized by co-pyrolysis of OS with reed, wheat straw, or sawdust, respectively, to systematically investigate their synergistic effects on structural and adsorption properties. The results revealed that AC prepared with a 7:3 mass ratio of OS to reeds at 700℃ exhibited the highest specific surface area of 363.0 m 2 /g, significantly outperforming the other two composite ACs. The surface morphology and distribution of oxygen-containing functional groups of the composite ACs were distinctly influenced by the inherent characteristics of the biomass used. Batch experiments demonstrated that the AC composite synthesized from OS and reed at a mass ratio of 7:3 exhibited the optimal adsorption capacity, with values of 11.7 mg/g for Pb 2 ⁺ and 10.6 mg/g for Cd 2 ⁺, both of which were superior to those of AC prepared solely from OS. Kinetic and isothermal analyses revealed that the adsorption processes of Pb 2 ⁺ and Cd 2 ⁺ onto the composite ACs were best described by the pseudo-first-order kinetic model and Langmuir isotherm model, respectively. Mechanistic investigations indicated that the adsorption mechanism primarily involved three synergistic processes: pore filling, complexation, and electrostatic attraction. This study provides a green strategy for the high-value utilization of OS and biomass, while offering an efficient adsorbent for heavy metal-contaminated wastewater treatment.