Optimization of Phosphate Adsorption Using Activated Carbon Derived from Pangium edule Shell

This study investigated the efficiency of activated carbon from Pangium edule shells for removing phosphate from aqueous solution.The adsorption capacity of the synthesized activated carbon was determined to be 19.8392 mg g−1.Various isotherm models were used to analyze the adsorption process,Henry,Freundlich,SIP,and Halsey isotherm fitting showed r2 values close to 1.0.These isotherms indicated a combination of physisorption and chemisorption mechanisms,with heterogeneity and multilayer formation playing important roles.A pseudo-second-order model described the adsorption kinetics well,suggesting chemisorption as the dominant mechanism with an r2 value of 1.0 and a rate constant k_(2) of 1.2550 min^(-1).The optimization was carried out using central composite design(CCD)using 3 factors(contact time(minutes),adsorbent dosage(mg),and initial phosphate concentration(ppm))with 3 levels.The CCD output was analyzed using response surface methodology(RSM)to obtain the optimum level of each factor.A contact time of one to two hours and an adsorbent dosage of more than 80 mg was recommended.Optimal removal was achieved at initial phosphate concentrations between 800 and 1150 ppm.Morphological analysis using scanning electron microscope(SEM)showed a highly irregular surface structure of activated carbon,while X-ray Diffraction(XRD)patterns indicated the presence of amorphous carbon.Fourier Transform Infrared(FTIR)analysis identified functional groups contributing to the adsorption process and Energy Dispersive X-ray Spectroscopy(EDX)analysis confirmed the presence of phosphate on the carbon surface after adsorption.In conclusion,activated carbon from P.edule shells has significant potential in phosphate removal,with a combination of high adsorption capacity,effective adsorption mechanism,and favorable kinetics,making it a promising material for water treatment.