Abstract
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.
Highlights
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
The peaks observed from the diffractogram indicate crystalline phase of POFA adsorbent, which determined as quartz with 89.7 wt% and calcium silicate, Ca2SiO4 with 10.3 wt%
This study has shown that POFA is an effective low cost and readily available adsorbent for Cr(VI) removal from aqueous solution
Summary
Anthropogenic activities such as skin processing, electroplating, pigment industry and metal mining-based industry had the potential to be a source of chromium contamination in soil and natural water sources (Bibi et al, 2016; Choppala et al, 2013). Trivalent chromium is less toxic compared to hexavalent chromium, and it functioned as a major micronutrient for glucose metabolism in the human body (Gheju et al, 2016; Shahid et al, 2017). Trivalent chromium can be oxidized into hexavalent chromium, causing serious environmental concern and danger to human health. Dermatitis, kidney and liver failure are examples of human toxicity upon inhalation, ingestion or dermal absorption of the hexavalent chromium exposure from soils and water bodies or wastewater
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