Showing papers by "Khairiraihanna Johari published in 2016"

Process analysis of mercury adsorption onto chemically modified rice straw in a fixed-bed adsorber

Abstract: The potential application of chemically modified rice straw (RSGM) was investigated in a fixed-bed adsorber as an extension of our previous batch adsorption studies. The effect of flow rates (2 mL/min, 4 mL/min and 8 mL/min), Hg(II) concentrations (50 mg/L, 100 mg/L, and 200 mg/L), and bed heights (1.5–4.5 cm) on the breakthrough characteristics of the fixed-bed adsorber was investigated. The adsorption isotherm data were best fitted to the Langmuir isotherm model, while the breakthrough data were found to be in good agreement with the Thomas and Yoon–Nelson models. The adsorbent bed regeneration results indicate a good adsorption–desorption reversibility with retaining adsorption performance of more than 90% after four cycles. The process design of the fixed-bed adsorber was demonstrated using the height of an equivalent transfer unit (HETU) method. The prediction of breakthrough curve was successfully carried out by scaling-up the Yoon–Nelson constants obtained from empty bed contact time (EBCT) plots.

Separation of dissolved oil from aqueous solution by sorption onto acetylated lignocellulosic biomass - equilibrium, kinetics and mechanism studies

Abstract: The potential use of lignocellulosic biomass as oil sorbents was demonstrated through acetylation of mercerized pineapple leaves (M-PAL) using acetic anhydride with catalysts ( N -bromosuccinimide and pyridine) in order to enhance its surface hydrophobicity and thus oil sorption capacity for treatment of dissolved oil contaminated wastewaters. The raw and acetylated PAL sorbents, before and after oil sorption, were characterized by a scanning electron microscope (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The oil sorption experiment was evaluated in batch sorption mode using dissolved o/w solution prepared by mixing crude oil and double-distilled water. It was found that the M-NBS-PAL sorbent yielded better oil sorption performance than R-PAL sorbent due to the replacement of hydroxyl group which has more hydrophobic acetyl group on the PAL surfaces, with strong affinity towards oil. The batch equilibrium data were fitted well by Langmuir isotherm model with the maximum sorption capacity ( q m ) of 37.45 and 90.91 mg/g for the R-PAL and M-NBS-PAL sorbents, respectively. The oil sorption process was thermodynamically feasible and exothermic, while the nature of interaction could be described via the physisorption mechanism. The kinetic sorption data were found to be fitted well into the pseudo-second order kinetic model. The sorption–desorption cycle was repeated four times whereby isopropanol was used as a desorbing agent and the results were comparable with freshly prepared sorbent. Finally, the present findings indicate that the lignocellulosic biomass could be a potential alternative as sorbent precursors for oil removal from oil contaminated wastewaters.

High removal efficiency of Hg(II) and MeHg(II) from aqueous solution by coconut pith—Equilibrium, kinetic and mechanism analyses

Abstract: This study was conducted to investigate the high efficiency of coconut pith (CP) adsorbent in removing Hg(II) and MeHg(II) ions from aqueous solution. The CP adsorbent was characterized using a scanning electron microscope (SEM), nitrogen adsorption-desorption (NAD) analysis, determination of pH at zero point charge (pHpzc), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Adsorption performance of the CP adsorbent at various parameters was conducted by varying the initial pH of solution, adsorbent dosage, initial pH, temperature, and contact time. It was found that adsorption capacity, adsorption rate and enthalpy of the Hg(II) adsorption were higher compared to the MeHg(II). The adsorption capacity of Hg(II) was 2.60 mmol/g, which was five times higher than MeHg(II). The adsorption isotherm analysis showed that the Hg(II) and MeHg(II) adsorption data fitted to the Langmuir and Freundlich models, respectively. The overall mechanism of both mercury adsorptions is a combination of physical and chemical processes in which the film diffusion was the rate controlling-step. The adsorbent regenerability study results showed that the Hg(II) adsorption remained stable up to five adsorption cycles, which was better than MeHg(II). The selectivity studies reveal the potential application of the CP adsorbent for the treatment of oilfield produced water (OPW) and natural gas condensate (NGC) that are rich in mercury ions as well as other cations.

High removal performance of dissolved oil from aqueous solution by sorption using fatty acid esterified pineapple leaves as novel sorbents

Abstract: This paper demonstrates the potential use of the lignocellulosic biomass of pineapple leaves (PALs) as an oil sorbent by mercerization and esterification with long chain fatty acids in order to enhance the surface hydrophobicity and thus the oil sorption capacity for the treatment of dissolved oil contaminated wastewater. The mercerized pineapple leaves (M-PALs) were esterified with lauric acid (LA) and stearic acid (SA) in pyridine–p-toluenesulfonyl chloride (Py–TsCl) solution to yield M-LA-PAL and M-SA-PAL sorbents, respectively, which were then characterized alongside the raw PAL (R-PAL) sorbent using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), CHNS/O analysis and Brunauer–Emmett–Teller (BET) surface area analysis to study the changes of the surface morphology, functional groups, elemental composition and specific surface area of the sorbents. It was found that M-SA-PAL gave the highest sorption capacity (138.89 mg g−1) followed by M-LA-PAL (107.67 mg g−1) and R-PAL (35.59 mg g−1), which are generally lower than dispersed oil sorption capacities. The oil sorption process was found to be exothermic in nature. The data analysis indicated that the sorption process obeyed the Langmuir isotherm and pseudo-second order kinetic models with film diffusion as the rate limiting step, which is similar to some of the reported dispersed oil sorption results. The sorbent regeneration was repeated four times using isopropanol–water (1:1, v/v) solution as a desorbing agent and the sorption results were found to be comparable with the freshly prepared sorbent. Finally, the present findings indicate that a lignocellulosic biomass such as PAL could be a potential alternative sorbent precursor for oil removal from oil contaminated wastewaters.

Surface modifications of agrowaste biomass for Hg(II) and MeHg(II) removal from aqueous solution, oilfield produced water and natural gas condensate

Abstract: The removal process of Hg(II) and MeHg(II) from aqueous solution by surface modified agrowaste biomass (AWB) was studied. The surface modifications were carried out by methods of mercerization, oxidative delignification, acid treatment, and biological treatment using laccase. The modifications promoted disruption of AWB structural surfaces and thus changed their physical and chemical properties as well as Hg(II) and MeHg(II) adsorption performances. The adsorption efficiency of Hg(II) was higher than MeHg(II) for all AWB adsorbents. The adsorption capacity of Hg(II) and MeHg(II) for AWB-Pure was 0.97 and 0.17 mmol/g, respectively. The highest adsorption capacity of Hg(II) and MeHg(II) was respectively observed for the AWB-Laccase (0.98 ± 0.04 mmol/g) and AWB-NaOCl/NaOH (0.40 ± 0.07 mmol/g). The adsorption selectivity of modified AWB adsorbents towards Hg(II) and MeHg(II) studied using oilfield produced water and natural gas condensate samples was found to be lower as compared to AWB-Pure, but higher selectivity was observed for other metals. The renewability studies show that the pure and modified AWB adsorbents had similar adsorption performance characteristics. The high Hg(II) adsorption efficiency (η > 90 %) was observed up to the third adsorption cycle, while for the MeHg(II), it decreased after each adsorption–desorption cycle.