High-efficiency removal of phosphate ions using treated Carpobrotus edulis biomass: Optimization, mechanism study, cost analysis, and industrial wastewater application

Abstract

This study focuses on the effects of alkaline treatment on the capacity of a Mediterranean plant called Carpobrotus edulis to absorb phosphate ions. The specific surface areas of the plant native and plant treated were 8.86 and 19.45 m² g^-1, respectively, indicating a significant specific surface area of the plant treated. A number of functional groups were determined, particularly C-O, NH₂, C-H, and

-OH, which promote the binding of the phosphate ions to the adsorbent. The SEM also shows that the adsorbent has a homogeneous texture with deep voids and significant porosity. After treatment with an alkaline solvent, soluble organic matter was reduced by 75.14 %, 86.16 %, and 82.22 % for biological oxygen demand, chemical oxygen demand, and organic matter, respectively. We could perfectly fit the kinetic data using the pseudo-second order model, while the Langmuir model proved an excellent fit for the equilibrium data. The modified plant maximum amount of phosphate ion adsorption is 909.09 mg g^-1 under the optimal conditions: biomass ratio of 3.75 g L^-1, contact time of 10 min, pH = 9.2 at 35°C. Thermodynamic values show that adsorption is realizable, spontaneous, and endothermic. The prepared biomaterial (costing 0.765 $ per 20 grams) was easily regenerated using an aqueous NaOH solution, with a slight reduction in its adsorption capacity (55.65 %) up to five cycles. The results of Taguchi experimental design and response surface methodology showed that initial concentration, temperature, and ratio are the most significant factors influencing elimination efficiency, with contributions of 98.39 %, 0.62 %, and 0.03 %, respectively. Biomaterial performance has been proven in the lentil seed germination test, as well as its effectiveness in removing phosphate ions from wastewater.