Effective remediation of lead(II) wastewater by Parkia speciosa pod biosorption: Box-Behnken design optimisation and adsorption performance evaluation

Remediation of lead(II) wastewater using sustainable and effective methods is necessary due to the adverse health impacts of lead(II). As such, Parkia speciosa (PS) pod which is a non-toxic agricultural waste was evaluated for its effectiveness in the biosorption of lead(II) from aqueous phase. The interactive impacts of multiple parameters (temperature, concentration, pH and dosage) on the biosorption efficiency of lead(II) as well as the process optimisation was investigated by Box-Behnken design. It was determined that at the optimised conditions (55 °C, 79.42 mg/L concentration, 4.47 pH and 2 g/L dosage), the achievable maximum biosorption capacity was 31.363 mg/g. The kinetics of lead(II) biosorption was best represented by the pseudo-second-order kinetic model while the process equilibrium correlated well to the Langmuir isotherm. Characterisation of the PS biowaste before and after the biosorption process confirmed the removal of lead(II). The reusability of exhausted PS biosorbent was best performed using 0.15 mol/L phosphoric acid. Overall, the results strongly support the feasibility of PS biowaste as a sustainable and effective biosorptive material for the remediation of lead(II) wastewater.