Development of aerated concrete waste/white cement composite for phosphate adsorption from aqueous solutions: Characterization and modeling studies

•AC and AAC as low-cost alternative adsorbents for phosphate removal.•Activation with white cement enhances adsorption (46.3%) and desorption (51.3%).•Pore filling, ligand exchange, attraction and precipitation in adsorption.•Repulsion from competition PO4−3 and P-displaced hydroxides by OH- in desorption. Adsorbing phosphate (PO4−3) from aqueous solutions onto concrete-based construction waste represents a low-cost, nontoxic, and sustainable technique. The novelty of this paper focuses on the adsorption and desorption of PO4−3 from aqueous solutions using autoclaved concrete (AC) chemically activated with white cement (AAC), representing an innovative adsorbent. Pseudo-second-order model better represent adsorption for AC (0.29 mg g−1; pH 6.35) and AAC (0.54 mg g−1; pH 6.53). The experimental data adjusted better with Freundlich and Langmuir models for AC (8.87 mg g−1) and AAC (3.90 mg g−1), suggesting physisorption and chemisorption, respectively. The presence of calcite could promote ligand exchange onto adsorbent surfaces. For desorption, pseudo-first-order model better explained for AC (0.19 mg g−1) and pseudo-second-order model for AAC (0.39 mg g−1). Sips model better fitted the equilibrium data (0.45 mg g−1 AC; 1.97 mg g−1 AAC), related to ionic exchange and electrostatic repulsion. Phosphate adsorption tends to be more reversible in AC. The chemical activation with white cement enhanced the phosphate removal and recovery by the alternative low-cost autoclaved aerated concrete. Finally, AC and AAC presented potential of reducing phosphate with 64.7% and 92.6% for raw wastewater and 83.1% and 84.8% for primary-treated effluent of a corn flour processing, respectively. [Display omitted]