High ammonium concentration in groundwater represents a major public health concern in Hanoi, Vietnam. In this study, mesoporous activated carbon was prepared from corncob using H3PO4 through a ...one-stage chemical activation process. Corncob activated carbon (CCAC) was subsequently treated with NaOH to enhance its cation exchange capacity. The results showed that this NaOH-modified corncob activated carbon (M-CCAC) exhibited a large specific surface area (1097 m2/g) and high total pore and mesopore volumes (0.804 cm3/g and 0.589 cm3/g, respectively). The batch experiments indicated that the NH4+-N removal was strongly dependent on the coexisting cations and pH of the solution, while in the kinetic experiments adsorption equilibrium was quickly reached within 60 min. The activation energy was calculated to be 49.7 kJ/mol. The maximum Langmuir adsorption capacity of M-CCAC exhibited the following order: 17.03 mg/g at 20 °C > 15.4 mg/g at 35 °C > 11.99 mg/g at 50 °C. The NH4+ adsorption process was spontaneous (–ΔG°) and exothermic (–ΔH°), and it increased the randomness (+ΔS°) in the system. The column experiments were conducted using real underground water to analyze the effects of different flow rates (1–3 mL/min), influent concentrations (10–40 mg/L), and bed heights (8.07–23.9 cm) on the adsorption capacity. The maximum adsorption capacity (8.69 mg/g) was achieved at a flow rate of 2 mL/min, an initial concentration of 40 mg/L, and a column height of 15.8 cm. Ion exchange was found to be the principal mechanism that controls ammonium adsorption, while pore-filling and electrostatic attraction played minor roles in the process. This study proved that M-CCAC is an effective adsorbent to remove ammonium from real groundwater.
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•M-CCAC characterized by BET surface area, TGA, FTIR, SEM, Boehm titration, CEC, and pHPZC.•SBET and Vtoal of M-CCAC before (1097 m2/g and 0.804 cm3/g) and after adsorption (1052 and 0.792).•Approximately 45%–75% of total NH4+ concentration in solution removed within 5 min.•Langmuir maximum adsorption capacity (Qomax): M-CCAC (17.03 mg/g) > CCAC (11.99) > CC (2.051).•Qomax/CEC (0.94/0.69 = 1.35) ratio of M-CCAC greater than 1.0.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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•The fundamental aspects of wettability and surface tension phenomena are presented and discussed.•The latest etching developments and recent promising applications are discussed.•The ...advantages and drawbacks of superhydrophobic materials of preparation have been identified.•The rugosity of the surface is crucial to obtain a superhydrophobic surface.•Optically transparent and highly stable superhydrophobic coatings are needed to protect solar cells.
With the recent progress in nanotechnology and material engineering, nano-based coatings have become multifunctional, smarter, efficient, versatile and durable. Superhydrophobic coatings are an important class of the smart coating family, which has gained recognition in coating science over the last few years. The uniqueness of superhydrophobic coatings arises from the various phenomenal innovations, and its development is expected to continue in the next decades. The bioinspired superhydrophobic surfaces are commonly obtained by designing a double-scale structure by using nanotechnology, followed by the addition of water repellent compounds. It lacks an overview article describing on the recent progress in superhydrophobic coatings and surfaces. In this perspective article, various fundamental aspects of wettability and related phenomena are discussed. We present and compare the existing methods for the preparation of superhydrophobic coatings. Properties of superhydrophobic coatings such as self-cleaning, anti-icing, anti-fouling, and anti-bacterial features were also introduced. The review also discusses various superhydrophobic technological breakthroughs and future trends in the preparation and application of these materials.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in water and wastewater has recently been reported. According to the updated literature, the stools and masks of the ...patients diagnosed with coronavirus disease (COVID-19) were considered as the primary route of coronavirus transmission into water and wastewater. Most coronavirus types which attack human (possible for SARS-CoV-2) are often inactivated rapidly in water (i.e., the survival of human coronavirus 229E in water being 7 day at 23 °C). However, the survival period of coronavirus in water environments strongly depends on temperature, property of water, concentration of suspended solids and organic matter, solution pH, and dose of disinfectant used. The World Health Organization has stated that the current disinfection process of drinking water could effectively inactivate most of the bacterial and viral communities present in water, especially SARS-CoV-2 (more sensitive to disinfectant like free chlorine). A recent study confirmed that SARS-CoV-2 RNA was detected in inflow wastewater (but not detected in outflow one). Although the existence of SARS-CoV-2 in water influents has been confirmed, an important question is whether it can survive or infect after the disinfection process of drinking water. To date, only one study confirmed that the infectivity of SARS-CoV-2 in water for people was null based on the absence of cytopathic effect (CPE) in infectivity tests. Therefore, further studies should focus on the survival of SARS-CoV-2 in water and wastewater under different operational conditions (i.e., temperature and water matrix) and whether the transmission from COVID-19-contaminated water to human is an emerging concern. Although paper-based devices have been suggested for detecting the traces of SARS-CoV-2 in water, the protocols and appropriate devices should be developed soon. Wastewater and sewage workers should follow the procedures for safety precaution against SARS-CoV-2 exposure.
•SARS-CoV-2 coronavirus detected in water and wastewater.•Transmission route of SARS-CoV-2 into water through stool and mask of infected patient.•Coronavirus often inactivated rapidly in water.•Paper-based devices suggested for detecting traces of SARS-CoV-2 in water.•Existing disinfection processes possibly sufficient to kill SARS-CoV-2 in water.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study used three types of agricultural waste, Citrus maxima peel, passion fruit shell, and sugarcane bagasse, to produce biosorbents for copper(II), cadmium(II), nickel(II), and lead(II) metal ...ion removal in a fixed-bed column. The biosorbent properties were characterized using scanning electron microscopy, zeta potential analysis, Fourier transform infrared spectroscopy, and cation exchange capacity. The adsorption capacities were determined using the Thomas model for various pH values and flow rates. The results indicated that biosorbents possess carboxylic acid groups, which function as exchangeable cation and complexation sites for removing heavy metals. The biosorbents exhibited great adsorption capacity. KCI Citation Count: 71
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The mechanism and capacity of adsorption of cadmium (Cd) on orange peel (OP)-derived biochar at various pyrolysis temperatures (400, 500, 600, 700 and 800°C) and heating times (2 and 6 h) were ...investigated. Biochar was characterized using proximate analysis, point of zero charge (PZC) analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. Equilibrium and kinetic experiments of Cd adsorption on biochar were performed. The results indicated that the pH value at PZC of biochar approached 9.5. Equilibrium can be reached rapidly (within 1 min) in kinetic experiments and a removal rate of 80.6-96.9% can be generated. The results fitted the pseudo-second-order model closely. The adsorption capacity was estimated using the Langmuir model. The adsorption capacity of Cd on biochar was independent of the pyrolysis temperature and heating time (p>0.01). The maximum adsorption capacity of Cd was 114.69 (mg g(-1)). The adsorption of Cd on biochar was regarded as chemisorption. The primary adsorption mechanisms were regarded as Cπ-cation interactions and surface precipitation. Cadmium can react with calcite to form the precipitation of (Ca,Cd)CO3 on the surface of biochar. The OP-derived biochar can be considered a favourable alternative and a new green adsorbent for removing Cd(2+) ions from an aqueous solution.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Contaminants in water bodies cause potential health risks for humans and great environmental threats. Therefore, the development and exploration of low-cost, promising adsorbents to remove ...contaminants from water resources as a sustainable option is one focus of the scientific community. Here, we conducted a critical review regarding the application of pristine and modified/treated biosorbents derived from leaves for the removal of various contaminants. These include potentially toxic cationic and oxyanionic metal ions, radioactive metal ions, rare earth elements, organic cationic and anionic dyes, phosphate, ammonium, and fluoride from water media. Similar to lignocellulose-based biosorbents, leaf-based biosorbents exhibit a low specific surface area and total pore volume but have abundant surface functional groups, high concentrations of light metals, and a high net surface charge density. The maximum adsorption capacity of biosorbents strongly depends on the operation conditions, experiment types, and adsorbate nature. The absorption mechanism of contaminants onto biosorbents is complex; therefore, typical experiments used to identify the primary mechanism of the adsorption of contaminants onto biosorbents were thoroughly discussed. It was concluded that byproduct leaves are renewable, biodegradable, and promising biosorbents which have the potential to be used as a low-cost green alternative to commercial activated carbon for effective removal of various contaminants from the water environment in the real-scale plants.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
The capacity and underlying mechanism of hydrochars derived from commercial D-glucose and wasted orange peels (designated as pristine-hydrochars) and further modified with nitric acid (designated as ...oxidized-hydrochars) to adsorb methylene blue were investigated. Both pristine- and oxidized-hydrochars were characterized by scanning electron microscopy, Brunauer–Emmet–Teller-specific surface area, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and mass titration. The maximum methylene blue adsorption capacity at 30°C estimated by the Langmuir model was found to follow the order: mGH (246 mg/g) > mOPH (107 mg/g) > OPH (59.6 mg/g) > GH (54.8 mg/g). Six adsorption mechanisms were elucidated, in which the electrostatic interaction and hydrogen bonding were identified as the primary methylene blue-hydrochar adsorptive interaction; furthermore, because the nitric acid modification process enhanced oxygen- and nitrogen-containing functional groups and unsaturated bonds on the surface of oxidized-hydrochars, the π–π and n–π interaction became minor pathways for methylene blue adsorption onto oxidized-hydrochars. Our results suggest that modified hydrochars could be used as environmentally friendly adsorbents alternative to activated carbon in dealing with methylene blue contamination in aqueous solutions.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
•New grafting copolymerization using acrylic acid and ammonium cerium nitrate developed.•Hydrochar, biochar, and activated carbon used as carbonaceous feedstocks for grafting.•Grafting materials ...exhibiting excellent adsorption capacity than their feedstocks.•The order for maximum adsorptive amounts (mol/kg): Cu > Cd > Pb.•Grafted hydrochar possessing the highest adsorption capacity.
Oxygen-containing groups on the surfaces of materials (i.e., –COOH and –OH) are vital to the adsorption of toxic metals. Acrylic acid is used as a green grafter to enhance the density of these groups in carbonaceous materials, whereas ammonium cerium nitrate is used as an initiator. Hydrochar (prepared via hydrothermal carbonization at 190 °C), biochar (generated via pyrolysis at 800 °C), and activated carbon (AC; generated via chemical activation with K2CO3 at 800 °C) derived from ginger residues are used as feedstock materials for the grafting process. Carbonaceous materials are characterized using scanning electron microscopy, X-ray photoelectron spectrometry, Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy, and zeta potential measurements. Cu2+, Cd2+, and Pb2+ are selected as adsorbates. Equilibrium adsorption experiments for the three metal ions on ungrafted and grafted carbonaceous materials are conducted at 25 °C and pH 5.0. Results indicated that the oxygen content in the grafted material is higher than that in the ungrafted material. Grafting can increase the number of OH and COOH functional groups on the carbonaceous materials, thus resulting in more metal ions being absorbed. The Langmuir maximum adsorption capacity (Qmax) of the carbonaceous materials for the toxic metal ions (mol/kg) is ranked in the order Cu2+ > Cd2+ > Pb2+. The amount of potentially toxic metal ions adsorbed on the ungrafted and grafted (abbreviated as G) materials are in the order hydrochar > AC > biochar. The Qmax values of hydrochar (72.8, 74.7, and 109.3 mg/g), biochar (53.6, 69.1, and 53.9 mg/g), AC (54.4, 73.1, and 101.8 mg/g), G-hydrochar (130.9, 146.0, and 271.4 mg/g), G-biochar (92.6, 143.6, and 153.6 mg/g), and G-AC (96.3, 146.1, and 259.1 mg/g) for the adsorbing metals (Cu2+, Cd2+, and Pb2+) are higher than that of commercial activated carbon (21.83, 22.13, and 25.15 mg/g, respectively). The adsorption capacity of the grafted hydrochar is restored after five adsorption–desorption cycles. The primary adsorption mechanisms are complexation and ion exchange.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study investigated the phenomenon and mechanism of adsorption of methylene green 5 (MG5) on three pristine biosorbents: golden shower pod (GS), coconut shell (CC), and orange peel (OP). The ...results showed that the biosorbents possessed low specific surface areas, but abundant functional groups. Adsorption was strongly affected by the solution's pH and ionic strength. As revealed in the kinetic study, equilibrium was rapidly established, requiring low activation energies; a removal rate of 30%-87% was achieved within 1 min. The maximum Langmuir adsorption capacities at 30°C exhibited the following order: GS (106 mg/g) > OP (92 mg/g) > CC (59 mg/g). Thermodynamic experiments suggested that the adsorption occurred spontaneously (−ΔG°) and exothermically (−ΔH°). The primary adsorption mechanisms involved electrostatic attraction, hydrogen bonding formations, and n-π interaction. Thermogravimetric analysis (TGA) revealed that three biopolymer components (i.e., hemicellulose, cellulose, and lignin) played controlling roles in the adsorption process. Thus, these three agricultural residues can be considered potential low-cost adsorbents for efficient dye adsorption applications.
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BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
•Properties and mechanisms of Cr(VI) adsorption onto LDH-based materials reviewed.•Such materials: high anion exchange capacity and positively charged external surface.•Identified mechanism: anion ...exchange, adsorption-coupled reduction, electrostatic attraction.•Adsorption-coupled reduction: identified by some advanced techniques from 2016.•Thermodynamic parameters: ΔG° <0, ΔH° >0, and ΔS° >0 in the most observation cases.
An attempt has been made in this review to provide some insights into the possible adsorption mechanisms of hexavalent chromium onto layered double hydroxides-based adsorbents by critically examining the past and present literature. Layered double hydroxides (LDH) nanomaterials are typical dual-electronic adsorbents because they exhibit positively charged external surfaces and abundant interlayer anions. A high positive zeta potential value indicates that LDH has a high affinity to Cr(VI) anions in solution through electrostatic attraction. The host interlayer anions (i.e., Cl−, NO3−, SO42−, and CO32−) provide a high anion exchange capacity (53–520 meq/100 g) which is expected to have an excellent exchangeable capacity to Cr(VI) oxyanions in water. Regarding the adsorption-coupled reduction mechanism, when Cr(VI) anions make contact with the electron-donor groups in the LDH, they are partly reduced to Cr(III) cations. The reduced Cr(III) cations are then adsorbed by LDH via numerous interactions, such as isomorphic substitution and complexation. Nonetheless, the adsorption-coupled reduction mechanism is greatly dependent on: (1) the nature of divalent and trivalent salts utilized in LDH preparation, and the types of interlayer anions (i.e., guest intercalated organic anions), and (3) the adsorption experiment conditions. The low Brunauer–Emmett–Teller specific surface area of LDH (1.80–179 m2/g) suggests that pore filling played an insignificant role in Cr(VI) adsorption. The Langmuir maximum adsorption capacity of LDH (Qomax) toward Cr(VI) was significantly affected by the natures of used inorganic salts and synthetic methods of LDH. The Qomax values range from 16.3 mg/g to 726 mg/g. Almost all adsorption processes of Cr(VI) by LDH-based adsorbent occur spontaneously (ΔG° <0) and endothermically (ΔH° >0) and increase the randomness (ΔS° >0) in the system. Thus, LDH has much potential as a promising material that can effectively remove anion pollutants, especially Cr(VI) anions in industrial wastewater.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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