Modified biosorbents for dissolved oil removal from produced water
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Date
2016
Authors
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Publisher
Universiti Teknologi Malaysia
Abstract
The difficulty in the removal of dissolved oil from oil-in-water containing wastewaters such as produced water has created a serious problem due to its toxicity that could lead to severe impact to human and the environment. The dissolved oil is rather difficult to be removed than dispersed oil due to their high solubility and lower concentration in water. Sorption process has arisen as one of the most popular organic pollutant removal methods due to its simplicity in design and cost-effective. The performance and cost of the sorption system depends primarily on the sorbents. The modification of agrowastes as biosorbents has gained considerable interests recently. In the present study, pineapple leaves (PAL) were thus selected as an agrowaste model precursor for biosorbent preparation for removal of dissolved oil. The PAL underwent surface modifications to yield acetylated PAL (M-NBS-PAL), fatty acid (lauric and stearic acid) esterified PAL (M-LA-PAL and M-SA-PAL), and etherified PAL followed by surfactant coating (M-CTA-SDS-PAL) biosorbents. The modified PAL biosorbents were then characterized against the raw PAL (R-PAL) using a scanning electron microscope, Fourier transform infrared spectrometer, x-ray photoelectron spectrometer, and CHNS/O analyser. The results revealed that the morphology, surface chemistry, elemental compositions of the PAL biosorbents have been altered after the modifications. The batch sorption results showed that the dissolved oil sorption capacity was dependent on the initial pH, initial concentration, contact time, temperature, and types of biosorbents. The maximum oil sorption capacity obtained for R-PAL, M-NBS-PAL, M-LA-PAL, M-SA-PAL, and M-CTASDS-PAL were 62.5, 107.5, 181.82, 204.08, and 212.77 mg/g, respectively. The isotherm and kinetic analysis showed that the dissolved oil sorption data of the PAL biosorbents obeyed the Langmuir isotherm and pseudo-second order models. The experimental results indicated that the dissolved oil sorption process was controlled by the physical phenomenon with the film diffusion as the rate-limiting step. The thermodynamic study proved that the sorption process was feasible, spontaneous, and exothermic in nature. The regeneration study revealed that the modified PAL biosorbents could be regenerated and reused repeatedly for at least four adsorptiondesorption cycles and the sorption results were still comparable with freshly prepared PAL biosorbents. These experimental evidences have ultimately demonstrated that agrowastes such as PAL could potentially be used as low-cost precursors for biosorbent not only for the removal of dissolved oil but also for other organic pollutants through appropriate modification methods
Description
Thesis (PhD. (Chemical Engineering))
Keywords
Sewage—Purification—Oil removal, Sewage—Purification—Organic compounds removal, Sewage—Purification—Biological treatment, Sorbents