Tailored olive pomace biochar anchored with CaAl layered double oxides for phosphate remediation from food industry wastewater: Role of pyrolysis and mechanistic insights
Alaa Abushawish, Ismail W. Almanassra, Muataz Ali Atieh, Omar Awayssa
Abstract
Phosphate (PO 4 3− ) release from food-processing effluents is a major driver of eutrophication, yet many existing removal methods remain inefficient, chemical-intensive, and generate substantial secondary waste. Here, olive pomace was upcycled into biochar doped with calcium‑aluminum layered double oxides (CaAl LDOs), with two synthesis strategies, co-pyrolysis (CaAl LDO-BC) and two-step pyrolysis (BC@CaAl LDO), systematically investigated. Characterization confirmed the structural integration of CaAl LDO into the carbon framework, with co-pyrolysis yielding higher surface area (11.75 m 2 /g), enriched oxygen (36 At.%), and more complete oxide dispersion than BC@CaAl LDO (6.87 m 2 /g, 21.4 At.% oxygen). CaAl LDO-BC exhibited 97.9 % PO 4 3− removal at 1 g/L from a 100 mg/L solution, a maximum capacity of 222.5 mg/g, and a rapid equilibrium within 30 min. Mechanistic insights from kinetic, isotherm, thermodynamic modeling, and XPS/FTIR analyses revealed a chemisorption-dominant uptake process. CaAl LDO-BC also maintained strong PO 4 3− adsorption under mildly acidic conditions, high selectivity in the presence of competing ions (>95 % removal), and achieved 99.9 % removal from real food-industry wastewater containing 174.2 mg PO 4 3− /L. Its estimated production cost (~10.5 US$/kg) falls within the typical biochar cost range, further supporting its practical feasibility. These findings highlight co-pyrolysis as an effective synthesis strategy and CaAl LDO-BC as a sustainable and high-performance adsorbent. • CaAl LDO–biochars synthesized via co- and two-step pyrolysis from olive pomace • Co-pyrolyzed composite presented a superior structure and adsorption performance. • CaAl LDO-BC achieved rapid P uptake (30 min) with a capacity of 222.5 mg/g. • Near-complete P removal (99.9 %) was achieved from food industry wastewater. • P adsorption was driven by complexation, ion exchange, and precipitation mechanisms.