This study investigated the removal of hexavalent chromium, Cr(VI) from aqueous solution by adsorption using palm oil fuel ash (POFA), an agricultural waste from the palm oil industry. POFA adsorbent was characterized by X-ray diffraction (XRD) analysis. Batch adsorption study revealed that the optimum conditions for the removal were as follows: pH 2, adsorbent dosage 80 g/L and contact time of 6 min, which resulted in 92% removal and 0.464 mg/g maximum adsorption capacity. Adsorption isotherm and kinetic studies showed that Freundlich isotherm and pseudo-second-order kinetic models fitted best to the experimental data. Column adsorption study at 5 mL/min of flow rate showed that 90% removal was obtained at 2 min of contact time which represented its breakthrough point. The column reached saturation at 30 min and the maximum column adsorption capacity recorded was 0.412 mg/g. The column adsorption behavior showed good fit with both Thomas and Yoon-Nelson kinetic models. These findings suggested that the utilization of POFA as a low-cost adsorbent to remove Cr(VI) from wastewater, either in batch or fixed bed adsorption system is not only effective, but concurrently will help to reduce wastes from the palm oil industry.

Archidendron jiringa seed peel extract was used to aid the coagulation-flocculation process to ultimately remove lead from synthetic residual water. The effectiveness of this method was studied to obtain an alternative approach that is easy to be handled with low cost and energy in removing the lead from residual water. Optimum parameters were analyzed to determine the effectiveness of lead removal, including pH, alum dose, and A. jiringa seed peel extract dose. A study on the coagulation-flocculation process with and without the aid of A. jiringa was also conducted. The optimum pH, the alum dose, and the A. jiringa seed peel extract dose were 9.0, 2.44 g/l, and 60.2 mg/l, respectively. The percentage of lead removal with the aid of A. jiringa seed peel extract was 79%, and the percentage was dropped to only 47% without the extract. A significantly higher rate in the coagulation-flocculation process due to the presence of A. jiringa seed peel extract proved its effectiveness in removing lead from wastewater.

Archidendron jiringa seed peel extract was used to aid the coagulation-flocculation process to ultimately remove lead from synthetic residual water. The effectiveness of this method was studied to obtain an alternative approach that is easy to be handled with low cost and energy in removing the lead from residual water. Optimum parameters were analyzed to determine the effectiveness of lead removal, including pH, alum dose, and A. jiringa seed peel extract dose. A study on the coagulation-flocculation process with and without the aid of A. jiringa was also conducted. The optimum pH, the alum dose, and the A. jiringa seed peel extract dose were 9.0, 2.44 g/l, and 60.2 mg/l, respectively. The percentage of lead removal with the aid of A. jiringa seed peel extract was 79%, and the percentage was dropped to only 47% without the extract. A significantly higher rate in the coagulation-flocculation process due to the presence of A. jiringa seed peel extract proved its effectiveness in removing lead from wastewater.