Low-cost biogenic waste for phosphate capture from aqueous system

Premised on the principle of waste minimization and affordable water and wastewater treatment system, the ability of waste African land snail shell (SS), as a sorbent, in the capture of phosphate from aqueous system was evaluated. Batch sorption process assessment of the effects of process variables showed that pH had no influence on phosphate sorption while anionic interference and organic load impacted negatively on the magnitude of phosphate uptake. Analysis of the sorption process using different kinetic models showed that the reversible first order and pseudo first order kinetic models gave poor descriptions of the process (r2 = 0.6977–0.8819) while the pseudo second order kinetic model gave the best description of the process (r2 > 0.99). Equilibrium isotherm analysis of the sorption process data showed that the Freundlich isotherm gave the best description of the process than the Langmuir and Temkin isotherm models. Estimation of the energy of sorption gave a value of 0.3318 kJ/mol, which is a pointer to the fact that electrostatic interaction did not dominate the mechanism of interaction between phosphate and SS. A simple economic evaluation of the process showed that the monolayer sorption capacity of the SS for phosphate (222.22 mg/g) was higher than that of other sorbents that have been screened for phosphate sorption from aqueous system and the phosphate laden SS could be used as soil conditioner cum fertilizer in agricultural practices.

► SS is a low cost biogenic sorbent for PO4-3 sorption from aqua system.
► Anionic interference and organics negatively impacted the SS sorption capacity.
► SS-PO4-3 interaction was not dominated by electrostatic attraction.
► Equilibrium is achieved faster at higher initial sorbate concentration.
► PO4-3 laden sorbent could be used as fertilizer cum soil conditioner.