Natural deep eutectic solvent (fructose-glycine) functionalized-celite/ polyethylene glycol hydrogel nanocomposite for phosphate adsorption: Statistical analysis

The increasing usage of phosphate fertilizers for agricultural purposes has led to an augmented level of phosphorus in watercourses negatively impacting the ecosystems and water quality warranting its amputation from polluted water. This article describes the preparation of a novel natural deep eutectic solvent (NADES) functionalized-celite/polyethylene glycol hydrogel nanocomposite (NADES-Cel/PEG HNC) for adsorptive phosphate removal from water. The XRD, FTIR, SEM coupled with EDX spectroscopy, TEM, BET analysis, and pHpzc measurement were used to characterise the prepared material. Central composite design (CCD) in response surface methodology (RSM) was used for experimental design to analyse the individual and combined impact of five operational parameters on equilibrium adsorption capacity (Qe), and evaluate the optimal operating conditions by numerical optimization, which were obtained as: contact time (60 min), adsorbent dosage (1.0 g/L), initial [PO43-] (80 mg/L), initial solution pH (3.5), and temperature (304 K). The adsorption process was best explicated via Langmuir adsorption isotherm with a noteworthy saturation capacity, Qm of 111.80 mg PO43-/g at 298 K, and was favourable (S* = 0.99), feasible (ΔG° = -7.02 kJ/mol), exothermic (ΔH° = -8.39 kJ/mol) and physical in nature. The uptake mechanism largely involved H-bonding, electrostatic interaction, n-π interaction and pore-filling. Uptake kinetics of PO43- was best explicated by pseudo-second order model, and the rate-determining step involved both intraparticle and liquid film diffusion mechanisms. The admirable performance of NADES-Cel/PEG HNC was signified by its competent adsorption efficacy and effectual reusability. The pertinence of the hydrogel nanocomposite for treatment of real wastewater was tested. Hence, NADES-Cel/PEG HNC might prove to be a pragmatic adsorbent for decontamination of PO43- from an aqueous environment.