Helen Kong

High removal efficacy of Hg(II) and MeHg(II) ions from aqueous solution by organoalkoxysilane-grafted lignocellulosic waste biomass

An effective organoalkoxysilanes-grafted lignocellulosic waste biomass (OS-LWB) adsorbent aiming for high removal towards inorganic and organic mercury (Hg(II) and MeHg(II)) ions was prepared. Organoalkoxysilanes (OS) namely mercaptoproyltriethoxylsilane (MPTES), aminopropyltriethoxylsilane (APTES), aminoethylaminopropyltriethoxylsilane (AEPTES), bis(triethoxysilylpropyl) tetrasulfide (BTESPT), methacrylopropyltrimethoxylsilane (MPS) and ureidopropyltriethoxylsilane (URS) were grafted onto the LWB using the same conditions. The MPTES grafted lignocellulosic waste biomass (MPTES-LWB) showed the highest adsorption capacity towards both mercury ions. The adsorption behavior of inorganic and organic mercury ions (Hg(II) and MeHg(II)) in batch adsorption studies shows that it was independent with pH of the solutions and dependent on initial concentration, temperature and contact time. The maximum adsorption capacity of Hg(II) was greater than MeHg(II) which respectively followed the Temkin and Langmuir models. The kinetic data analysis showed that the adsorptions of Hg(II) and MeHg(II) onto MPTES-LWB were respectively controlled by the physical process of film diffusion and the chemical process of physisorption interactions. The overall mechanism of Hg(II) and MeHg(II) adsorption was a combination of diffusion and chemical interaction mechanisms. Regeneration results were very encouraging especially for the Hg(II); this therefore further demonstrated the potential application of organosilane-grafted lignocellulosic waste biomass as low-cost adsorbents for mercury removal process.

Surfactant modification of banana trunk as low-cost adsorbents and their high benzene adsorptive removal performance from aqueous solution

The banana trunk was modified using cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulphate (SDS), poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (Pluronic 123), and 4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (Triton X-100) to develop novel low-cost adsorbents for benzene removal from aqueous solution. The surface morphology and functional groups of the synthesized adsorbents were determined by a field emission scanning electron microscope (FESEM) and a Fourier transform infrared (FTIR) spectrophotometer. The Brunauer, Emmett and Teller (BET) analysis and X-ray photoelectron spectroscopy (XPS) were also conducted to study adsorbent characteristics. The benzene adsorptive performance of the synthesized adsorbents was evaluated in a batch adsorption experiment at various experimental conditions. It was found that the highest benzene adsorption capacity (280.890 × 10−3 mmol g−1) was obtained for M-TX100-BT. The fundamental adsorption studies revealed that the benzene adsorption process was found to be thermodynamically non-spontaneous and all were fitted well by the Langmuir isotherm model. The adsorption kinetic data obeyed the pseudo-second kinetic model with the film diffusion as the rate-limiting step. The application prospects of the Triton X-100 modified banana trunk adsorbent were demonstrated through the regeneration study which revealed that it can also be repeatedly used for at least up to five-adsorption/desorption cycles and its adsorption capacity was comparable to the literature data of similar adsorbents. Thus, banana trunk agrowaste could be an alternative low-cost adsorbent precursor for the adsorptive benzene removal from an aqueous solution.

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

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.