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.

A study of batch and column adsorption using A. jiringa seed shell as a natural adsorbent to remove methylene blue from aqueous solution was carried out. This study aimed to determine the effectiveness of A. jiringa seed shell in removing methylene blue as well as to determine the isotherm and adsorption kinetics of methylene blue by A. jiringa seed shells. Parameters in the batch study showed optimum pH for adsorption was at pH 7 with the optimum contact time of 60 minutes whereas the adsorbent dose obtained was 12 g/l. The percentage removal of methylene blue increased with elevated temperature while the ionic strength reduced the adsorption capacity in the dye uptake. Langmuir isotherm was suitable for this study rather than Freundlich model due to the higher regression value: R 2 = 0.9999. The most suitable kinetic model for this study was the pseudo second order, compared to pseudo first order, Elovich and intra particle with the value of regression: R 2 = 0.9158. This column adsorption study used several different flow rates: 15 mL/min, 18 mL/min, 21 mL/min, 24 mL/min and 27 mL/min for 75 minutes long. The breakthrough time was lesser: 10 minutes in higher flow rates (24 mL/min and 27 mL/min), which indicated the shorter time for the adsorbent to be saturated. Thomas and Yoon & Nelson's models were proven to be more suitable compared to Bohart-Adams model for the fixed bed adsorption study.

Leachate is a form of pollution from landfills with pollutants in organic and inorganic forms. Stabilized leachate is characterized by the presence of organic materials with high ammoniacal nitrogen concentrations (>400mg/L), high chemical oxygen demand (COD) concentrations (<4000mg/L) and the ratio of BOD/COD is low (<0.1). In this study, struvite precipitation used to remove high ammonia content and coagulation-flocculation using poly-aluminium chloride (PAC) as coagulant agent and cationic polymer as flocculant agent used for COD and colour removal. Response surface methodology (RSM) is applied to determine the optimum parameters and interaction effects of the four main factors that influence the efficiency of treatment used; coagulant dosage, flocculant dosage, pH and Mg-N-P ratio on COD, NH3-N and colour removal. Optimum parameters obtained from the study were the coagulant dosage of 2250 mg/L, flocculant dosage of 14 mg/L, pH 7, and Mg: N: P ratio 1.1. The combination of struvite precipitation and coagulation-flocculation method results a percentage of removal of COD 48.6%, NH3-N 92.8% and color 98.8%

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.