Using Orange Peels (OP) as a Bio-Adsorbent for Removal of phosphate from Wastewater

The research objective is to study the removal of phosphate from wastewater by Orange Peel (OP). The effectiveness and efficiency of phosphate adsorption by orange peels were investigated by studying the influence of adsorbent mass, particle size, time, pH, and phosphate concentrations. 0.05 g of adsorbent could remove 1.540 mg/g of phosphate within 105 min. A size of 0.3 mm was the suitable size that achieved the highest phosphate removal of 1.570 mg/g. The optimum pH was around pH 6.5. Commonly used isotherm and kinetic models are described and discussed to choose the most suitable model. The best-fit isotherm was the Langmuir, exhibiting an adsorption capacity (Qm) of 4.046 mg/g. The pseudo-second-order was the most suitable, with a calculated capacity close approximation of the experimental. The model indicates a multiple adsorption chemisorption mechanism dominated by the interaction between phosphate anion and adsorbent by a complex with hydroxyl groups and/or by exchanging ions. The phosphate could also be desorbed by the H-bond interaction between phosphate and H-bond donor groups. The COD and BOD tests revealed that the orange peels gave the best result for removing phosphate from wastewater, where the COD and BOD concentrations of treated wastewater decreased from 394 mg/L to 215 mg/L and from 314 mg/L to 170 mg/L, respectively. FT-IR measurements were also conducted before and after adsorption, which showed variable adsorption ratios of the adsorbent.