Helen Kong

The aim of this work is to convert agroforestry residue to a novel adsorbent (M-1CTA-SDS-BT) used for adsorptive benzene sequestration from aqueous solution. In this study, the anionic surfactant-coated-cationized banana trunk was synthesized and characterized for batch adsorption of benzene from aqueous solution. The surface morphology, surface chemistry, surface area, and pore properties of the synthesized adsorbents were examined. It was proven that surface cationization successfully increased the benzene adsorption capacity of sodium dodecyl sulfate-coated adsorbents. The Langmuir isotherm model satisfactorily described the equilibrium adsorption data. The maximum benzene adsorption capacity (q_max) of 468.19 μmol/g was attained. The kinetic data followed the pseudo-second-order kinetic model in which the rate-limiting step was proven to be the film diffusion. The batch-adsorbent regeneration results indicated that the M-1CTA-SDS-BT could withstand at least five adsorption/desorption cycles without drastic adsorption capacity reduction. The findings demonstrated the adsorptive potential of agroforestry-based adsorbent as a natural and cheap material for benzene removal from contaminated water.

Adsorption of inorganic mercury [Hg(II)] and organic methylmercury [MeHg(II)] ions onto dye‐affinity agrowaste (dye‐AW) was investigated. The dye‐affinity adsorbents were prepared by the chemical‐thermal reaction between the agrowaste (AW) and dye solutions [i.e., Reactive Red 120 (RR), Reactive Black B (RB), Methylene Blue (MB), and Methyl Orange (MO)] under an alkaline condition. An almost perfect removal of Hg(II) was observed for all adsorbents, while for MeHg(II), the dye‐affinity adsorbents have a higher removal efficiency than a pristine adsorbent. The maximum adsorption capacity (Q_{e, max}) of mercury ions onto the Reactive Red 120‐modified AW (RR‐AW) was 2.60 mmol g⁻¹ for Hg(II) and 0.76 mmol g⁻¹ for MeHg(II). The adsorption rate of Hg(II) was faster than MeHg(II), and both kinetic data followed the pseudo‐second order kinetic model with the diffusion steps controlled by the film diffusion. The regenerated adsorbent showed very encouraging results especially toward Hg(II). The promising results were also obtained by using oilfield produced water (OPW) and natural gas condensate (NGC) samples. These studies finally demonstrated that the agricultural wastes initially loaded with dyes have the potential to be good mercury adsorbents. © 2018 American Institute of Chemical Engineers Environ Prog, 38: S54–S67, 2019

The persistence of antibiotics in sewage wastewater treatment plants in recent years has emerged as a serious issue. This study therefore evaluated three types of natural zeolites (i.e., NZ01, NZ02, and NZ03) for the removal of selected antibiotics namely tetracycline (TC) and oxytetracycline (OTC) from aqueous solution. The physical and chemical properties of the natural zeolites were characterized using various analytical techniques and the antibiotic removal studies were carried out in a batch adsorption experiment evaluated at various experimental conditions. The highest adsorption capacity was 62.5 and 76.3 μmol/g for TC and OTC, respectively, observed for NZ02 at pH values between 7 and 8. The adsorption of TC and OTC followed the Langmuir and Temkin isotherm models, respectively, whereas the adsorption kinetic data obeyed the Elovich kinetic model. The regeneration study on NZ02 indicated that it can still remove TC and OTC after five adsorption/desorption cycles. The removal efficiency of TC and OTC also improved from approximately 5–39 and 28%, respectively, by addition of NZ02 during the coagulation/flocculation process. These results thus demonstrated the applicability of the natural zeolites, especially NZ02, for the removal of TC and OTC from aqueous solution; hence the potential for the application in sewage treatment process for removal of antibiotics through either conventional adsorption/desorption or adsorptive coagulation/flocculation (ACF) process.

Cetyltrimethylammonium bromide‐coated agrosorbents were successfully synthesized through firstly mercerization of raw banana trunk (Raw‐BT) with alkali (M‐BT) and finally coating with cetyltrimethylammonium bromide (M‐CTAB‐BT). The characterization was done using an energy dispersive X‐ray spectrophotometer, a Fourier transform infrared spectrophotometer and a field emission scanning electron microscope. The Brunauer, Emmett, and Teller analysis was also conducted. The benzene adsorption performance of BT agrosorbents was improved by mercerization and surfactant coating according to the following order: Raw‐BT (340.25 × 10⁻ mmol/g) < CTAB‐BT (382.41 × 10⁻³ mmol/g) < M‐CTAB‐BT (535.62 × 10⁻³ mmol/g). The adsorption data obeyed the Langmuir and pseudo‐second order (PSO) kinetic models with film diffusion as the rate‐limiting step. The agrosorbent regeneration as well as comparison to literature data indicated the modified BT and thus the agrowaste biomass could be alternative agrosorbent precursors for removing benzene from aqueous solutions. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 305–317, 2018