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• Cetyltrimethylammonium bromides (CTAB)-functionalized silica nanoparticles (MSN) were successfully synthesized. • Physicochemical properties changed upon CTAB functionalization. • The presence of CTAB in MSN showed excellent adsorption performance towards OTC. • Q e.max of MSN (449.89 µmol g−1) was higher than FSN (57.06 µmol g−1). • MSN shows encouraging adsorption capacity compared to other adsorbents. The cetyltrimethylammonium bromide (CTAB)-functionalized silica nanoparticles (MSN) were prepared using a combined sol-gel and adsorption steps. The nitrogen adsorption-desorption surface analysis shows the MSN has a lower surface area than the unmodified (or free) silica nanoparticles (FSN). The energy dispersive X-ray (EDX) and Fourier transform infrared (FTIR) analysis confirmed the presence of CTAB in MSN with maximum CTAB coverage of (0.74 ± 0.04) mmol/g. The maximum adsorption capacity of oxytetracycline (OTC) onto MSN performed in the batch adsorption process, Q e.max is 449.89 µmol g−1, which is higher than FSN (57.06 µmol g−1). The adsorption depends on pH value, OTC concentration, temperature, and contact time. The thermodynamic parameters indicate the process as exothermic in nature and spontaneous. The isotherm data fits well with the Redlich-Peterson model, while the pseudo-second order (PSO) kinetic model is found to be suitable to describe the kinetic data with the film diffusion as the rate-limiting step. The electrostatic, hydrogen bonding and hydrophobic interactions are mainly responsible for the OTC adsorption onto the synthesized adsorbents. The reusability studies found that the adsorbent could be recycled without drastic adsorption capacity reduction. The successful decoration of the CTAB onto the surface of the silica nanoparticles provides an effective method in the development of promising adsorbents for antibiotic removal from wastewater. [ABSTRACT FROM AUTHOR]

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 (Qe, 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 [ABSTRACT FROM AUTHOR]

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 [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The mercerized coconut fiber (CF-NaOH) was prepared by treating the pristine coconut fiber (CF-Pure) with NaOH solution. The morphology and chemical composition of CF-Pure changed after mercerization process. The maximum Ag(I) adsorption capacity of the CF-Pure and CF-NaOH was 0.502 and 0.612 mmol/g, in which the equilibrium data fitted to the Freundlich and Langmuir isotherm models, respectively. The Ag(I) adsorption rate also increased by using CF-NaOH and the kinetic data of both CF-Pure and CF-NaOH obeyed the pseudo-second order kinetic model. The enhancement of Ag(I) adsorption selectivity from photographic waste solution was also observed for the CF-NaOH. [ABSTRACT FROM AUTHOR]

The modified rice husks were characterized in terms of morphology (scanning electron microscopy), functional groups (Fourier transform infrared spectroscopy), surface charge (pH), and elemental composition which indicate the treatments that led to significant changes to its surface chemistry. Batch adsorption studies showed that the highest adsorption capacity of Hg(II) was 89 and 118 mg/g obtained by sulfur-functionalized rice husk (RH-CS) and organosilane-grafted rice husk (RH-GM), respectively. The reusability of raw rice husk (RH-Raw) and alkali-treated rice husk (RH-NaOH) was superior to RH-CS and RH-GM; even though their adsorption capacities were slightly lower. However, their selectivity was comparable to that of the RH-CS and RH-GM. In addition, the results demonstrated the potential application of rice husk-based adsorbents for treating Hg(II) containing wastewaters such as produced water from oil and gas exploration activities. [ABSTRACT FROM AUTHOR]

In this study, elemental mercury (EM) adsorbents were synthesized using tetraethyl orthosilicate (TEOS) and 3-mercaptopropyl trimethoxysilane as silica precursors. The synthesized silica gel (SG)-TEOS was further functionalized through impregnation with elemental sulphur and carbon disulphide (CS2). The SG adsorbents were then characterized by using scanning electron microscope, Fourier transform infra-red spectrophotometer, nitrogen adsorption/desorption, and energy-dispersive X-ray diffractometer. The EM adsorption of the SG adsorbents was determined using fabricated fixed-bed adsorber. The EM adsorption results showed that the sulphur-functionalized SG adsorbents had a greater Hg° breakthrough adsorption capacity, confirming that the presence of sulphur in silica matrices can improve Hg° adsorption performance due to their high affinity towards mercury. The highest Hg° adsorption capacity was observed for SG-TEOS(CS2) (82.62 μg/g), which was approximately 2.9 times higher than SG-TEOS (28.47 μg/g). The rate of Hg° adsorption was observed higher for sulphur-impregnated adsorbents, and decreased with the increase in the bed temperatures. [ABSTRACT FROM AUTHOR]

Thispaper presents the study of the adsorption characteristicsof sulfur-functionalized silica microspheres (S-SMs), synthesizedthrough co-condensation of tetraethyl orthosilicate with 3-mercaptopropyltrimethoxysilane (MPTMS) and bis(triethoxysilylpropyl) tetrasulfide(BTESPT) as sulfur ligands, with respect to the removal of Hg(II)from aqueous solutions. The synthesized adsorbentswere characterized using a scanning electron microscope, an X-raydiffractometer, a nitrogen adsorption–desorption analyzer,a Fourier transforminfrared spectrophotometer, and an energy dispersive X-ray diffractometer.The effects of pH, concentration, temperature, stirring time, andadsorbent reusability were studied via batch adsorption experiments.It was found that the optimal adsorption pH values for all synthesizedadsorbents were between 5.8 and 8.2. The adsorption capacity of SMswas 20.0 mg/g and increased to 37.0 and 62.3 mg/g for BTESPT-SMs andMPTMS-SMs, respectively. Hg(II) adsorption was found to be exothermicin nature and followed the chemisorption mechanism. The Langmuir isothermmodel was found to be the best fitted model for describing the isothermdata, while the kinetic data obeyed the pseudo-second-order kineticmodel, in which film diffusion was found to be the rate-controllingstep. The regeneration study using potassium iodide as a regenerationagent showed high reusability, up to five-cycle activity. [ABSTRACT FROM AUTHOR]

• CTAB encapsulated silica nanocapsules (SiNC-CTAB) were synthesized. • SiNC-CTAB shows higher adsorption capacity and faster rate than SiNC-FREE. • Maximum adsorption capacity of SiNC-CTAB was 124.50 mg g−1. • SiNC-CTAB show good reusability up to 4 consecutive adsorption cycles. The silica nanocapsules (SiNC) with CTAB (SiNC-CTAB) and free CTAB (SiNC-FREE) were prepared by the microemulsion polymerization process, in which the cetyltrimethylammonium bromide (CTAB) was used as a structure directive as well as a cationic functionalized agent. The structure and properties of these adsorbents were characterized by a field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), nitrogen adsorption–desorption (NAD) analyzer, Fourier transform infrared (FTIR) spectrophotometer, thermogravimetric analyzer (TGA) and pH at point zero charges (pH pzc) determination. The adsorbents were then characterized for their adsorption behavior towards Pd(II) ions in aqueous solution performed in a batch adsorption experiment. The maximum adsorption capacity of Pd(II) ions onto SiNC-CTAB obtained from the adsorption isotherm was 124.50 mg g−1, which was over 2.4 times higher than that of the SiNC-FREE (51.28 mg g−1). The diffusion modeling analysis by the Weber Morris model indicated that the film diffusion is the controlling step, while the chemical reaction modeling obeyed the pseudo-second order kinetic model. The SiNC-CTAB was found to be reusable in which a good adsorption performance of up to 4 adsorption cycles was observed. [ABSTRACT FROM AUTHOR]

Highlights • A facile synthesis method of sulfurized-char for Hgº adsorption was demonstrated. • Coconut pith and elemental sulfur were good precursor for sulfurized- charproduction. • Physicochemical properties of sulfurized-chars determined the Hgº adsorption. • Highest Hgº adsorption capacity (q e = 26077.7 μg/g) obtained for CPS300(1:1). Abstract Facile sulfurization of char from agrowaste of coconut pith (CP) and elemental sulfur was developed towards producing cheaper adsorbents for elemental mercury (Hgº) adsorption. It was found that physicochemical properties of the sulfurized chars changed with the initial CP to elemental sulfur ratio (CPS) and sulfurization temperatures, that generally affected the Hgº adsorption. The CPS ratio of 1:1 and sulfurization temperature of 300 ºC (i.e. CPS300(1:1)) resulted in outstanding Hg° adsorption performance. Characterization of the char indicates the presence of the organic compounds, organic sulfur and elemental sulfur species onto the adsorbents were likely favoring the Hgº adsorption. The adsorption capacity of CPS300(1:1) was higher than 26077.7 μg/g, since the adsorbents still did not reach breakthrough time even after 80 d of adsorption process. The study on the effect of bed temperature found that the adsorbent was still effective in removing Hgº at any temperature (50 ºC to 200 ºC). The sulfurized-char however was non-regenerable. [ABSTRACT FROM AUTHOR]

In this study, chars from coconut pith (CP) were prepared aiming for superior adsorption towards elemental mercury (Hg o ). The yield, proximate analysis, textural characteristics, surface functional groups and elemental composition analyses of the chars produced at pyrolysis temperature of 300 °C, 500 °C, 700 °C and 900 °C were compared. The surface area, pore volume, ash and carbon content of chars increased, while the yield and moisture content decreased with increasing pyrolysis temperatures. The changing of physical and chemical properties of the chars produced at variety pyrolysis temperature was much effect on the Hg o adsorption performance and definitely provides important information on the Hg o adsorption mechanism. The highest Hg o adsorption capacity was observed for CP900 (6067.49 μg/g), followed by CP700 (2395.98 μg/g), CP500 (289.76 μg/g), CP300 (1.68 μg/g), and CP (0.73 μg/g). The equilibrium data were well described by the Freundlich adsorption isotherm model. The pseudo-second order best described the kinetic data of the Hg o adsorption onto CP and CP300. For chars produced at higher pyrolysis temperature, however, the pseudo-zero order and pseudo-second order fitted well for the adsorption and breakthrough regions, respectively. The Hg o adsorption capacity of chars obtained from high pyrolysis temperature of CP significantly outperformed the commercial activated carbon (Darco KB-B) as well as superior to chars reported in the literature indicating the CP can be used as a precursor for preparation of chars as elemental mercury adsorbents. [ABSTRACT FROM AUTHOR]

Coconut husk (CH), consisting of coconut pith (CP) and coconut fiber (CF) is abundant and cheap, and has the potential to be used as adsorbent for elemental mercury (Hg 0 ) removal. CP and CF surfaces were modified by mercerization and bleaching methods and characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and analysis of moisture and ash. The elemental mercury adsorption measurements were carried out at the following conditions: initial Hg 0 concentration, 200 ± 20 μg/m 3 ; bed temperature, 50 ± 1 °C; N 2 flow rate, 0.05 L/min; mass of adsorbent, 50 mg; and adsorbent particle size of between 75 and 100 μm. The surface morphology and surface functional groups of adsorbents significantly changed after treatments and resulted in different Hg 0 adsorption performances. The highest Hg 0 adsorption capacity was observed for CP-NaOH (956.282 ng/g), followed by CP-Pristine (730.250 ng/g), CF-NaOCl (639.948 ng/g), CF-H 2 O 2 (634.347 ng/g), CF-NaOH (611.678 ng/g), CF-H 2 O 2 (531.277 ng/g), CP-NaOCl (501.126 ng/g), and CF (431.773 ng/g). The experimental breakthrough data for all the adsorbents produced a good fit to the pseudo-second order kinetic model. [ABSTRACT FROM AUTHOR]

Adsorptive efficacy of lignocellulosic waste char (LW-CHAR) and activated carbon (LW-AC) toward inorganic (Hg2+) and organic (MeHg+) mercury ions was studied. The LW-CHAR and LW-AC were, respectively, prepared by carbonization and KOH activation processes of lignocellulosic waste (LW) carried out at 700 °C. The Hg2+ adsorption onto the LW-CHAR was lower than LW-AC, however, an opposite result was observed for the MeHg+ indicating the nature of the surface interactions of both mercury ions to respective adsorbent surfaces was significantly different. The adsorption data analysis of both mercury ions was found however to only follow the Langmuir isotherm and pseudo-second order kinetic models whereby a combination of chemisorption and diffusional process was the governing mercury ions adsorption mechanism. [ABSTRACT FROM AUTHOR]

A novelmercapto-grafted rice straw (RS-GM) was synthesized and characterizedagainst raw rice straw (RS-Raw). The RS-GM yielded a better Hg(II)biosorption performance compared to RS-Raw as the incorporated-mercaptanfunctional group presented a strong affinity toward Hg(II). The isothermdata correlated well with the Langmuir isotherm model having maximumbiosorption capacity, qmaxof 103.10 mg/gand 161.30 mg/g for RS-Raw and RS-GM, respectively. The Hg(II) biosorptionis thermodynamically feasible, endothermic, and spontaneous in nature.The biosorption kinetic data were best-fitted into the pseudo-second-orderkinetic model. Further analysis suggested that the Hg(II) biosorptionprocess is governed by the intraparticle and external mass transferin which the film diffusion was the rate limiting step. The adsorption–desorptioncycle was repeated four times by using diluted HCI as desorbing agent,and the results were comparable to the unused biosorbent. The removalof Hg(II), which was also done in the produced water, was found tobe 96% by using RS-GM. [ABSTRACT FROM AUTHOR]

The char desiccated coconut adsorbent (DCWC) is prepared through a facile carbonization method in an open-air muffle furnace. The characterization analyses of the adsorbents show that the carbonized adsorbent has more significant pore structure, higher surface area and higher composition of elemental carbon all while retaining the same functional group as the pristine adsorbent. Among the carbonized adsorbent, surface area of DCWC500 is 134.640 m2/g, the highest among the carbonized adsorbent i.e. DCWC400 and DCWC300. The carbonization of the desiccated coconut waste materials resulted in higher adsorption capacity of the adsorbent where the recorded maximum monolayer capacity was 2.65 and 3.51 mmol/g for DCWP and DCWC500, respectively. The adsorptive uptake of Pb(II) by the adsorbents follows Langmuir isotherm and pseudo-second order kinetic model which indicates the process follows favourable monolayer adsorption process governed by chemical adsorption. Both DCWP and DCWC500 adsorbents are regenerable up to five (5) adsorption-desorption cycles of Pb(II) with the ability to retain Pb(II) removal above 85%. In respect to its application for Pb(II) removal in wastewater, both DCWP and DCWC performed a highly effective Pb(II) removal which indicate that the adsorbents are potential as an efficient and cost-friendly adsorbent alternatives for industrial application. • Higher pyrolysis temperature produces char with higher surface area, porosity and better surface chemistry. • Char adsorbent produced at higher temperature performed better adsorption capacity towards heavy metals ions. • Maximum monolayer capacity of the char adsorbent is 3.51 mmol/g while its pristine, 2.65 mmol/g. [ABSTRACT FROM AUTHOR]