Remediation of organic pollutant from the aqueous environment using in-house fabricated polyaniline-based hybrid composite (PANI-MnPBA/NiCoMnS) materials

Polyaniline-based hybrid material (PANI-MnPBA/NiCoMnS) was prepared by hydrothermal-solvothermal approach. Synthesized hybrid material was characterized through FTIR-spectroscopy, p-XRD, SEM, EDX, BET, and Zetasizer techniques. Hybrid material as adsorbent for removal of Congo red (CR) from water system showed excellent results such as 98 % removal efficiency and 254 mg/g adsorption capacity. Furthermore, various studies like adsorption isothermal, kinetic, thermodynamic, and statistical analysis were performed to understand the adsorption phenomenon. From various kinetic models, pseudo-first and second-order kinetic models, intra-particle and liquid film diffusion kinetic models, pseudo-first-order kinetic model, and liquid-film diffusion kinetic model both are most suitable for explaining the adsorption phenomenon due to the greater value of R2 (0.955) for CR. According to these kinetic models, physio-sorption and diffusion play a basic role in the adsorption of CR. Moreover, ΔG (-1779.508 kJ mol-1) and ΔH (61,760.889 kJ mol-1) values explained the spontaneous and exothermic nature of the adsorption process, respectively. Furthermore, for support of the adsorption mechanism via electrostatic attractions before and after the adsorption process FTIR results of as-synthesized adsorbent were measured (NH peaks before 3668.88, after 3541.41 cm-1). These results confirm electrostatic attraction for the adsorption process. Finally, the statistical model was added (n < 1), according to this model, adsorption follows a multi-anchorage approach and adsorbent contains enough sites for adsorption of CR.

Simultaneous removal of four aflatoxins using magnetic nanobentonite as a green and fast sorbent: kinetic, thermodynamic, and isotherm investigation

In the study, an adsorptive removal strategy as a straightforward and fast procedure was developed to remove four aflatoxins, including aflatoxin B1 (AF-B1), aflatoxin B2 (AF-B2), aflatoxin G1 (AF-G1), and aflatoxin G2 (AF-G2). A simple and green sorbent consisting of two components (activated nanobentonite and Fe3O4 nanoparticles) was synthesized based on three steps using acidic treatment, ultrasonic procedure, and chemical precipitation method. The sorbent was characterized by several techniques such as FTIR, FESEM, TEM, XRD, and VSM to determine the sorbent structure and morphology. An experimental design based on a central composite design was utilized to optimize factors in the removal of AFs. The optimum values of the factors (pH, sorbent amount, shaking rate) were 6.8, 0.076 g, and 160 rpm, respectively. Three models, including pseudo-first-order, pseudo-second-order, and intra-particle diffusion models, were used to investigate the kinetics of the removal process. The removal of AFs using magnetic nanobentonite was fitted with the pseudo-second-order model better than other models with an equilibrium time lower than 30 min. The thermodynamic data show that the adsorption of AFs on the sorbent is a spontaneous and feasible process due to negative values of the Gibbs-free energy change (ΔG) at different temperatures. Two models (Langmuir and Freundlich models) were chosen to study the isotherm of the removal procedure, indicating that the Freundlich model describes the results better than the Langmuir model. The maximum adsorption capacity of the sorbent for removing AF-B1, AF-B2, AF-G1, and AF-G2 is 357.14, 400.0, 370.37, and 400.0 mg g-1, respectively. The sorbent reusability was also evaluated to study the sorbent's ability for the removal of AFs, indicating that the sorbent was used for 5 cycles without a significant reduction in the ability to remove AFs.

Adsorptive removal of ciprofloxacin and sulfamethoxazole from aqueous matrices using sawdust and plastic waste-derived biochar: A sustainable fight against antibiotic resistance

We produced carbon-negative biochar from the pyrolysis of sawdust biomass alone (SB) and from the co-pyrolysis of sawdust and plastic waste (SPB). The co-pyrolysis approach in this study was driven by several hypothetical factors, such as increased porosity, surface chemistry, stability, as well as waste management. We applied pyrolyzed and co-pyrolyzed biochars for the removal of ciprofloxacin (CFX) and sulfamethoxazole (SMX). Due to its more alkaline and amorphous nature, SB showed better removal efficiencies compared to SPB. The maximum removals of CFX and SMX with SB were observed as ∼95% and >95%, respectively whereas with SPB were 58.8%, and 34.9%, respectively. The primary mechanisms involved in the adsorption process were H-bonding, electrostatic and π-π electron donor-acceptor interactions. Homogenously and heterogeneously driven adsorption of both antibiotics followed the pseudo-second-order kinetic model, implying electron sharing/transfer (chemisorption) mediated adsorption. The work is highly pertinent in the context of emerging concerns related to drivers that promote antimicrobial resistance.

An overview on human exposure, toxicity, solid-phase microextraction and adsorptive removal of perfluoroalkyl carboxylic acids (PFCAs) from water matrices

Perfluoroalkyl carboxylic acids (PFCAs) are sub-class of perfluoroalkyl substances commonly detected in water matrices. They are persistent in the environment, hence highly toxic to living organisms. Their occurrence at trace amount, complex nature and prone to matrix interference make their extraction and detection a challenge. This study consolidates current advancements in solid-phase extraction (SPE) techniques for the trace-level analysis of PFCAs from water matrices. The advantages of the methods in terms of ease of applications, low-cost, robustness, low solvents consumption, high pre-concentration factors, better extraction efficiency, good selectivity and recovery of the analytes have been emphasized. The article also demonstrated effectiveness of some porous materials for the adsorptive removal of the PFCAs from the water matrices. Mechanisms of the SPE/adsorption techniques have been discussed. The success and limitations of the processes have been elucidated.

Efficient adsorptive removal of aminoglycoside antibiotics from environmental water

Aminoglycoside antibiotics (AGs) in environmental water are emerging pollutants that must be removed to protect human health and the ecosystem. However, removing AGs from environmental water remains a technical challenge due to high polarity, stronger hydrophilicity and unique characteristics of polycation. Herein, a thermal-crosslinked polyvinyl alcohol electrospun nanofiber membrane (T-PVA NFsM) is synthesized and firstly leveraged as the adsorptive removal of AGs from environmental water. The thermal crosslinking strategy is demonstrated to enhance both the water resistance and hydrophilicity of T-PVA NFsM, thereby effectively interacting with AGs with high stability. Experimental characterizations and analog calculations indicate that T-PVA NFsM utilizes multiple adsorption mechanisms, including electrostatic and hydrogen bonding interactions with AGs. As a result, the material achieves 91.09%-100% adsorption efficiencies and a maximum adsorption capacity of 110.35 mg g^-1 in less than 30 min. Furthermore, the adsorption kinetics follow the pseudo-second-order model. After eight consecutive adsorption-desorption cycles, T-PVA NFsM with a simplified recycling process maintains a sustainable adsorption capability. Compared with other forms of adsorption materials, T-PVA NFsM has significant advantages such as less consumption of adsorbent, high adsorption efficiency and fast removal speed. Therefore, T-PVA NFsM-based adsorptive removal holds promise for eliminating AGs from environmental water.

Recent advances in luminescence and aptamer sensors based analytical determination, adsorptive removal, degradation of the tetracycline antibiotics, an overview and outlook

Tetracycline antibiotics (TCs), one of the important antibiotic groups, have been widely used in human and veterinary medicines. Their residues in foodstuff, soil and sewage have caused serious threats to food safety, ecological environment and human health. Here, we reviewed the potential harms of TCs residues to foodstuff, environment and human beings, discussed the luminescence and aptamer sensors based analytical determination, adsorptive removal, and degradation strategies of TCs residues from a recent 5-year period. The advantages and intrinsic limitations of these strategies have been compared and discussed, the potential challenges and opportunities in TCs residues degradation have also been deliberated and explored.

Fe3O4 modified chitosan based co-polymeric magnetic composite hydrogel: Synthesis, characterization and evaluation for the removal of methylene blue from aqueous solutions

The present research comprises the fabrication of magnetic Fe₃O₄ incorporated chitosan grafted acrylamide and N-vinylimidazole composite hydrogels (CANFe-1 to CANFe-7) via water mediated free radical polymerization technique using ammonium persulfate/tetramethyl ethylenediamine as initiator. The prepared magnetic composite hydrogel was characterized by FT-IR, TGA, SEM, XRD, and VSM analysis. A swelling study was performed to understand the swelling behavior and found CANFe-4 to be more efficient with maximum swelling hence entire removal studies were performed with CANFe-4. pH_PZC analysis was performed to determine pH sensitive adsorptive removal of cationic dye (methylene blue). pH dependent adsorption of methylene blue was dominant at pH = 8 with a maximum adsorption capacity of 860 mg/g. After the adsorptive removal of methylene blue from aqueous media, a composite hydrogel can conveniently be separated from the solution with the use of an external magnet. Adsorption of methylene blue is well explained with the Langmuir adsorption isotherm and Pseudo-Second-Order kinetic model that validates chemisorption. Moreover, it was found that CANFe-4 could be frequently applied for the adsorptive removal of methylene blue for 5 consecutive adsorption-desorption cycles with 92.4 % removal efficiency. Hence, CANFe-4 offers a promising recyclable, sustainable, robust, and efficient adsorbent for wastewater treatment.

Effective and stable adsorptive removal of Cadmium(II) and Lead(II) using selenium nanoparticles modified by microbial SmtA metallothionein

Metallothionein SmtA-modified selenium nanoparticles (SmtA-SeNPs), efficient adsorbents for Cd(II) and Pb(II), were synthesized in the present work. The ligand, microbial SmtA protein, was synthesized using an engineered strain Escherichia coli, posing the benefits of simplicity, safety, and high production. SmtA-SeNPs were spheres with diameters between 68.1 and 122.4 nm, containing amino, hydroxyl, and sulfhydryl functional groups with negatively charged (pH > 5). SmtA-SeNPs displayed better adsorption performance than dissociative SmtA and SeNPs. The adsorption of Cd(II) and Pb(II) mainly depends on the electrostatic attractions and the metal chelation of abundant functional groups. The maximum adsorption capacity was 506.3 mg/g for Cd(II) and 346.7 mg/g for Pb(II), which were higher than the values of most nanoparticles. In addition, SmtA-SeNPs were immobilized with a membrane filter to produce a SmtA-SeNPs filter, and the percentage removal of Cd(II) and Pb(II) increased from 26.75% to 98.13% for Cd(II) and from 9.95% to 99.20% compared with the blank filter. Moreover, the SmtA-SeNPs filter was regenerated using subacid deionized water, and the filter exhibited a stable removal ratio of Cd(II) and Pb(II) in ten continuous cycles of Cd(II)- or Pb(II)-containing wastewater treatment. The residual amounts of Cd and Pb met national standard levels of wastewater discharge.

Amine-bilayer-functionalized cellulose-chitosan composite hydrogel for the efficient uptake of hazardous metal cations and catalysis in polluted water

Herein, we represent a novel ecofriendly bilayer-amine group incorporated microcrystalline cellulose (MCC)/chitosan (CS) hydrogel, fabricated via integrating polydopamine (PDA) and polyethyleneimine (PEI) for reliable and effective extraction of copper (Cu²⁺), zinc (Zn²⁺), and nickel (Ni²⁺) ions from effluents. Owing to abundant adsorptive sites, the MCC-PDA-PEI/CS-PDA-PEI hydrogel showed excellent Cu²⁺, Zn²⁺, and Ni²⁺ adsorbabilities of ~434.8, ~277.7, and ~261.8 mg/g, respectively, in a single-ion adsorption system with the adsorption kinetics and isotherm complied with pseudo-second-order and Langmuir models, respectively. In a multi-ion adsorption system, hydrogel removes mixed metal cations with slightly higher selectivity for Cu²⁺. In accordance with X-ray photoelectron and Fourier-transform-infrared spectrometric analyses, a plausible binding mechanism of metal cations on the as-prepared hydrogel was proposed by chelation between hydrogel functional groups and metal ions. In the repetitive adsorption/desorption experiments, the hydrogel retained >40% metal ion adsorption and desorption capacities after four cycles. Furthermore, the Cu²⁺-adsorbing hydrogel could serve as a support for the in situ development of Cu nanoparticles, which showed excellent catalytic performance as demonstrated by the transformation of 4-nitrophenol (4-NP) to 4-aminophenol. This work provides a novel ecofriendly, reusable, and highly-efficient adsorbent, as well as a biocatalyst for remediation of heavy metal cations and 4-NP polluted effluents.

Nanocomposites of immobilized nano-zirconia on low-cost activated carbon derived from hazelnut shell for enhanced removal of 3-Nitro-4-Hydroxy-Phenylarsonic acid from water

3-Nitro-4-hydroxy-phenylarsonic acid (NHPA) as a veterinary drug can degraded into highly toxic inorganic arsenic and will be harmful to environment and food safety. Nanocomposites for the uptake of NHPA were obtained by efficiently immobilizing the nano-sized zirconium oxide onto hazelnut shell-based activated carbon using pyrolysis method. We found that the pyrolysis temperature played a crucial role in the adsorptive performances of the nanocomposites. The prepared nanocomposite at pyrolysis temperature of 600 °C with a mass ratio of ZrOCl₂/activated carbon of 1:3 exhibited a fast adsorption equilibrium for NHPA within 5 min, excellent adsorption capacity of 825.7 mg g^-1 and the higher adsorption capacity with the increase in temperature from 20 to 45 °C across a pH range of 4-6. 90% of the NHPA uptake was sustained in the NaNO₃ solution of 0.7 mol L^-1. The adsorption data were well simulated by the Langmuir and pseudo-second order equations. Thermodynamic parameters suggested that the uptake of the NHPA occurred spontaneously (ΔG⁰<0) with an endothermic characteristic (ΔH⁰>0). A synergetic effect of electrostatic attraction, As-O-Zr surface coordination and π-π interaction is the main adsorption mechanism of the nanocomposites for the removal of the NHPA.

Characterization of bio-adsorptive removal performance of strontium through ureolysis-mediated bio-mineralization

The adsorptive removal performance of strontium (Sr) through bio-mineralization metabolism under various parameters was evaluated in this study. The primary mechanism of bio-mineralization used in this study was the urea hydrolysis process through bacterial enzymatic catalysis. Bacillus sp, which was isolated from river sediment, was used as a ureolytic bacteria. Various environmental conditions were set as different initial concentrations of Sr (10, 50, 100, 200, and 500 mg/L), and various ratios of Mg/Ca (4, 2, 1, 0.5, and 0.25). The concentrations of Sr²⁺, Ca²⁺, and Mg²⁺ in the solution of the batch experiment were measured to identify the bio-mineralization performance and the removal rate of Sr. In addition, the main Sr removal mechanism of ureolytic bacteria was identified. As a result, for Sr removal of bacteria, the bio-mineralization mechanism was more predominant than the adsorption of Sr. The rapid growth and high nucleation site production were observed when the initial concentration of Sr²⁺ increased and the Mg/Ca ratio was lowered, resulting in high biomineralization performance and Sr removal rate. The main phases of carbonate minerals formed in the presence of Sr, Ca, and Mg were SrCO₃ and SrCa(CO₃)₂. Mg²⁺ could retard the bacterial growth and participate in the formation of carbonate minerals, when a large amount of Mg²⁺ was present. Furthermore, the desorption rate of Sr²⁺ from bacterial pastes containing the carbonate minerals increased as the concentration of HCl increased, although the carbonate minerals were in a stable state.

Treatment technologies to mitigate the harmful effects of recalcitrant fluoroquinolone antibiotics on the environ- ment and human health

Antibiotic proliferation in the environment and their persistent nature is an issue of global concern as they induce antibiotic resistance threatening both human health and the ecosystem. Antibiotics have therefore been categorized as emerging pollutants. Fluoroquinolone (FQs) antibiotics are an emerging class of contaminants that are used extensively in human and veterinary medicine. The recalcitrant nature of fluoroquinolones has led to their presence in wastewater, effluents and water bodies. Even at a low concentration, FQs can stimulate antibacterial resistance. The main sources of FQ contamination include waste from pharmaceutical manufacturing industries, hospitals and households that ultimately reaches the wastewater treatment plants (WWTPs). The conventional WWTPs are unable to completely remove FQs due to their chemical stability. Therefore, the development and implementation of more efficient, economical, convenient treatment and removal technologies are needed to adequately address the issue. This review provides an overview of the technologies available for the removal of fluoroquinolone antibiotics from wastewater including adsorptive removal, advanced oxidation processes, removal using non-carbon based nanomaterials, microbial degradation and enzymatic degradation. Each treatment technology is discussed on its merits and limitations and a comparative view is presented on the choice of an advanced treatment process for future studies and implementation. A discussion on the commercialization potential and eco-friendliness of each technology is also included in the review. The importance of metabolite identification and their residual toxicity determination has been emphasized. The last section of the review provides an overview of the policy interventions and regulatory frameworks that aid in retrofitting antibiotics as a central key focus contaminant and thereby defining the discharge limits for antibiotics and establishing safe manufacturing practices.

Aluminum-based metal-organic frameworks for adsorptive removal of anti-cancer (methotrexate) drug from aqueous solutions

A series of metal-organic frameworks (MOFs) based on aluminum-benzene dicarboxylates (MIL-53, NH₂-MIL-53, and NH₂-MIL-101) at different ratios have been synthesized, and their adsorption performances for methotrexate (MTX), an anti-cancer drug, have been investigated in terms of adsorption kinetics, isotherms, solution pH, thermodynamics, mechanism, and recyclability. Maximum adsorption values of 374.97, 387.82, and 457.69 mg/g were observed for MIL-53, NH₂-MIL-53, and NH₂-MIL-101 , respectively. Our study shows that adsorption capacity of MTX depends not only on surface area and pore volume but also on the zeta potential and the presence of suitable functional groups. Higher adsorption of NH₂-MIL-101 observed for MTX than the other synthesized MOFs may be attributed to its large surface area, large total pore volume, high positive zeta potential, and polar amino functional groups located on its surface, which are responsible for its increased interactions with MTX molecules. Adsorption isotherms and kinetics of MTX onto NH₂-MIL-101 followed the Langmuir and pseudo-second-order kinetic equations. Thermodynamic data suggest that adsorption of MTX onto NH₂-MIL-101 is spontaneous and exothermic, while the adsorption mechanism is governed by electrostatic interactions, π-π stacking interactions, and H-bonding. Regeneration and recyclability of NH₂-MIL-101 were also investigated by washing with ethanol to observe its decreased adsorption performance towards MTX. It was slightly decreased after seven adsorption-desorption cycles, indicating excellent regeneration and good structural stability under the chosen experimental conditions.

Adsorptive removal of pharmaceuticals from water using metal-organic frameworks: A review

Pharmaceutical pollution has emerged as a highly concerned issue due to its adverse effects. Elevated concentrations of pharmaceuticals in water should be regulated to satisfy the requirement for the provision of clean water. Metal-organic frameworks (MOFs) with high specific surface area, controllable porous structure, and facile modification can serve as promising adsorbents for the removal of pharmaceutical contaminants from water. In this review, a selected collection illustrating the reliable strategies and concepts to prepare the MOFs-based materials with superior water stability is described. In addition, recent progress on the adsorptive removal of pharmaceutical pollutant using burgeoning and functional MOFs is also summarized in terms of maximum capacity, equilibrium time, and regenerate ability. Meanwhile, to understand the adsorption mechanism, related interactions including coordination with unsaturated site, pore-filling effect, hydrogen bonding, electrostatic, and π-π stacking are further discussed. Finally, critical perspectives/assessment of future research emphasising on fabricating desirable MOFs and establishing structure-property relationships to facilitate capture performance are identified.

Superior removal of inorganic and organic arsenic pollutants from water with MIL-88A(Fe) decorated on cotton fibers

Arsenic contamination has attracted worldwide concerns, owing to its toxicity and severe threat to human and environment. It is urgent to develop efficient adsorbents to remove arsenic pollutants. Within this paper, both pristine MIL-88A(Fe) and MIL-88A(Fe) decorated on cotton fibers were successfully fabricated using an eco-friendly method. The pristine MIL-88A(Fe) displayed outstanding adsorption performances towards four selected arsenic pollutants, in which the adsorption capacities toward As(III), As(V), ROX and ASA were 126.5, 164.0, 261.4 and 427.5 mg g^-1, respectively. Additionally, MIL-88A(Fe) exhibited excellent removal efficiencies in a wide pH range and with the presence of different co-existing ions. It was proposed that the coordinative interactions of As-O-Fe between arsenic pollutants and MIL-88A(Fe) contributed to the superior adsorption performances. Furthermore, two MIL-88A(Fe)/cotton fibers composites were synthesized by both post synthesis (MC-1) and in-situ synthesis (MC-2), which demonstrated identically outstanding adsorption activities toward four selected arsenic pollutants. MC-1 and MC-2 enhanced the stability and reusability of MIL-88A(Fe), which was challenging issues of pristine MIL-88A(Fe) powder. Additionally, the fixed-bed column packed by MC-1 or MC-2 can continuously eliminate arsenic pollutants from the water flow. This work provided a new possibility of metal-organic frameworks to accomplish potentially large-scale application to purify the arsenic-contaminated water.

Nanocomposites of zero-valent Iron@Activated carbon derived from corn stalk for adsorptive removal of tetracycline antibiotics

The hybrid nanocomposites of zero-valent iron loaded the activated carbon derived from the corn stalk (ZVI@ACCS) was prepared and used to remove the antibiotics of tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) from aqueous solution. The adsorption amounts of three antibiotics (103.1 mg g^-1 for CTC, 72.9 mg g^-1 for OTC and 81.5 mg g^-1 for TC) were sensitive to the temperature and independent of pH in the range of 4.2-7.1 at 298 K through the synergistic interactions of the electrostatic attraction, the bridging complexation and the surface complexation. The equilibrium was performed within 20 min at 298 K. The spontaneous (ΔG^o<0) and endothermic (ΔH^o>0) adsorption of three antibiotics onto the ZVI@ACCS nanocomposites gave a better matching (r² > 0.99) with Langmuir and pseudo-second-order models.

Cationic metal-organic frameworks as an efficient adsorbent for the removal of 2,4-dichlorophenoxyacetic acid from aqueous solutions

Metal-organic frameworks (MOFs) material with high surface area, good chemical stability and multi-functionality, has become an emerging adsorbent for water treatment. A novel kind of quaternary amine anionic-exchange MOFs UiO-66 namely UiO-66-NMe₃⁺ was firstly synthesized for adsorptive removal of a widely used toxic herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solutions. The well-prepared UiO-66-NMe₃⁺ MOFs were fully characterized, and then the main parameters affecting the adsorption process including solution pH, adsorbent dosage and coexisting anions were systematically investigated. The maximum adsorption capacity of UiO-66-NMe₃⁺ toward 2,4-D reached as high as 279 mg g^-1, much higher than that of pristine UiO-66 and aminated UiO-66. The adsorption mechanism could be attributed to the electrostatic interactions efficiently enhanced by the functionalization of quaternary amine groups, combining with the π-π conjugations between the linkers in MOFs and 2,4-D molecules, leading to the better adsorption performance of UiO-66-NMe₃⁺. Additionally, the UiO-66-NMe₃⁺ could be well regenerated by simple solvent washing and exhibited a slight decline of adsorption capacity after seven successive recycle. Furthermore, satisfactory adsorption capacity and reusability of the MOFs in environmental water samples were attained. Comparing with reported activated carbon and resin materials, the UiO-66-NMe₃⁺ MOFs possessed higher adsorption capacity and shorter equilibrium time, as well as good reusability and practicality. The developed ion-exchange functionalized MOFs provided an ideal alternative for efficient adsorptive-removal of 2,4-D from complicated aqueous environment.

CuO-modified activated carbon for the improvement of toluene removal in air

We used an impregnation method to prepare CuO/AC (activated carbon) composite materials of different CuO content and characterized them via scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), and Fourier transform infrared spectroscopy (FT-IR). The effect of CuO content on toluene adsorption/desorption was evaluated. We explored the reusability of AC and AC03 (CuO modified AC with CuO loading 0.3 wt.%) adsorbents via toluene adsorption/desorption cycle testing. We used quasi-first- and quasi-second-order models, the Bangham model, and the Weber-Morris model to fit the toluene adsorption data. The introduction of CuO species evidently improved the adsorption performance of activated carbon toward toluene. The CuO content markedly affected the specific surface area, CuO dispersal, the numbers of oxygen-containing functional groups on the surface, and adsorption performance of the prepared composite adsorbents. Low CuO content was not favorable for the formation of active adsorption sites, while high content greatly reduced the specific surface area, and even covered active adsorption sites. The toluene adsorption performance varied in the order AC03 > AC02 > AC05 > AC08 > AC01 (AC03, AC02, AC05, AC08 and AC01 are CuO modifying AC with CuO loading 0.3, 0.2, 0.5 0.8 and 0.1 wt.%, respectively). The breakthrough time and toluene adsorption capacity of the AC03 composite adsorbent were 94 min and 701.8 mg/g, respectively, and the recycling efficiency was 92.8% after thermal desorption at 200°C. The adsorption process was best described by the Bangham model and adsorption could be divided into three stages.

Adsorptive nanocomposite membranes for heavy metal remediation: Recent progresses and challenges

Heavy metal contamination in aqueous system has attracted global attention due to the toxicity and carcinogenicity effects towards living bodies. Among available removal techniques, adsorptive removal by nanosized materials such as metal oxide, metal organic frameworks, zeolite and carbon-based materials has attracted much attention due to the large active surface area, large number of functional groups, high chemical and thermal stability which led to outstanding adsorption performance. However, the usage of nanosized materials is restricted by the difficulty in separating the spent adsorbent from aqueous solution. The shift towards the use of adsorptive composite membrane for heavy metal ions removal has attracted much attention due to the synergistic properties of adsorption and filtration approaches in a same chamber. Thus, this review critically discusses the development of nanoadsorbents and adsorptive nanocomposite membranes for heavy metal removal over the last decade. The adsorption mechanism of heavy metal ions by the advanced nanoadsorbents is also discussed using kinetic and isotherm models. The challenges and future prospect of adsorptive membrane technology for heavy metal removal is presented at the end of this review.

Adsorptive removal of polycyclic aromatic hydrocarbons by detritus of green tide algae deposited in coastal sediment

Rare information is available on the adsorptive removal of polycyclic aromatic hydrocarbons (PAHs) in the presence of algal detritus deposited in the coastal sediment during the outbreak of the green tide. The adsorptive removal of typical PAHs by Ulva prolifera (U. prolifera) detritus was firstly investigated since the algal detritus was of great importance for the biogeochemical cycle of coastal contaminants. The results showed that equilibrium adsorptive capacities of naphthalene, phenanthrene and benzo[a] pyrene on the U. prolifera detritus were 1.27, 1.97, and 2.49 mg kg^-1, respectively, at the initial concentration of 10 μg L^-1. The in situ monitoring using laser confocal scanning microscopy confirmed the adsorptive removal of PAHs by U. prolifera detritus. The adsorption of these PAHs was highly pH-dependent. The increase in salinity led to the increase in naphthalene removal rate, while the salinity showed scarce influence on the removal of phenanthrene and benzo[a] pyrene. There was a good linear relationship (R² ≥ 0.9892) between the removal efficiency of PAHs and the initial concentration of PAHs. Slow desorption kinetics and low desorption rate (<16%) indicated that the adsorptive removal of PAHs could be benign to the environment. These findings demonstrated that the occurrence of green tide could provide a new natural remediation approach for contamination of PAHs through the adsorptive removal by the detritus of green tidal algae deposited in the coastal sediment.

Recent advances on porous organic frameworks for the adsorptive removal of hazardous materials

Environmental pollution is one of the most serious problems facing mankind today, and has attracted widespread attention worldwide. The burgeoning class of crystalline porous organic framework materials, metal-organic frameworks and covalent organic frameworks present promising application potential in areas related to pollution control due to their interesting surface properties. In this review, the literature of the past five years on the adsorptive removal of various hazardous materials, mainly including heavy metal ions, harmful gases, organic dyes, pharmaceutical and personal care products, and radionuclides from the environment by using COFs and MOFs, is summarized. The adsorption mechanisms are also discussed to help understand their adsorption performance and selectivity. Additionally, some insightful suggestions are given to enhance the performance of MOFs and COFs in the adsorptive removal of various hazardous materials.

Functionalized magnetic nanomaterials for rapid and effective adsorptive removal of fluoroquinolones: Comprehensive experimental cum computational investigations

Alarming growth of pharmaceutical residues in aquatic environment has elevated concerns about their potential impact on human health. Taking cognizance of this, the present study is focussed on the coating of cobalt ferrite nanoparticles with different functionalities and to use them as adsorbents for pharmaceutical waste. The thickness of the coating was analysed using Small angle X-ray scattering technique. Thorough study of the isotherms and kinetics were performed suggesting monolayer adsorption and pseudo kinetic order model, respectively. To get an insight of the interactions liable for adsorption of fluoroquinolones over the functionalized magnetic nanoparticles computational studies were undertaken. The results demonstrated substantial evidence proposing remarkable potential of these nanostructures as adsorbents for different pollutants with an additional advantage of stability and facile recoverability with a view to treat wastewater.

Progress and prospect of adsorptive removal of heavy metal ions from aqueous solution using metal-organic frameworks: A review of studies from the last decade

The efficient removal of heavy metals (HMs) from the environment has become an important issue from both biological and environmental perspectives. Recently, porous metal-organic frameworks (MOFs), combining central metals and organic ligands, have been proposed as promising materials in the capture of various toxic substances, including HMs, due to their unique characteristics. Here we review recent progress in the field of water remediation from the perspective of primary HMs (including divalent metals and variable-valent metals) in water pollution and the corresponding MOFs (including virgin and modified MOFs, magnetic MOFs composites and so on) that can remove these metals from water. The reported values of various MOFs for adsorption of heavy metal ions were 8.40-313 mg Pb(II) g^-1, 0.65-2173 mg Hg(II) g^-1, 3.63-145 mg Cd(II) g^-1, 14.0-127 mg Cr(III) g^-1, 15.4-145 mg Cr(VI) g^-1, 49.5-123 mg As(III) g^-1, and 12.3-303 mg As(V) g^-1. The main adsorption mechanisms associated with these processes are chemical (including coordination interaction, chemical bonding and acid-base interactions) and physical (including electrostatic interaction, diffusion and van der Waals force) adsorption, which were discussed in detailed. Further efforts should be made towards expanding the repertoire of MOFs that effectively remove multiple targeted HMs, as well as exploring possible applications of MOFs in the removal of HMs from non-aqueous environments.

A Ti-doped γ-Fe2O3/SDS nano-photocatalyst as an efficient adsorbent for removal of methylene blue from aqueous solutions

Synthetic dyes are among the most important environmental pollutants in wastewaters. Consequently, elimination of the synthetic dyes from wastewaters using non-toxic materials and eco-friendly technologies has been of considerable interests. In this study, magnetically separable Ti-doped γ-Fe₂O₃ photocatalysts were synthesized for the removal of methylene blue (MB) from a dye-contaminated aqueous solution (as a model of dye-polluted wastewaters). Compared to the pristine γ-Fe₂O₃, the 1.78 v% Ti-doped γ-Fe₂O₃ significantly increased the adsorption of MB by 57% in the dark condition as a result of the improved BET surface area in this photocatalyst. Moreover, the contact time required for the photocatalytic degradation of MB by the 1.78 v% Ti-doped γ-Fe₂O₃ decreased due to the higher concentration of charge carriers in this photocatalyst than that of the pristine γ-Fe₂O₃. The effect of different experimental parameters on the adsorption property and photocatalytic activity of the 1.78 v% Ti-doped γ-Fe₂O₃ photocatalyst showed that the solution pH had a remarkable influence on the removal performance of this photocatalyst. Surface treatment of the 1.78 v% Ti-doped γ-Fe₂O₃ with sodium dodecyl sulfate (SDS) resulted in the formation of a negatively charged Ti-doped γ-Fe₂O₃/SDS photocatalyst, which showed a higher tendency for the adsorption and removal of MB than the untreated photocatalyst. Moreover, the MB removal efficiency of this photocatalyst was among the best performances that have been reported for the γ-Fe₂O₃-based photocatalysts. The synthesized photocatalysts were characterized by various techniques, and a plausible mechanism for the removal of MB from aqueous solutions by the Ti-doped γ-Fe₂O₃/SDS photocatalyst was purposed.

Adsorptive removal of microcystin-LR from surface and wastewater using tyre-based powdered activated carbon: Kinetics and isotherms

Microcystin LR (MC-LR) is a highly toxic compound and it is known for its adverse health effect on both humans and animals. Due to the ineffectiveness of conventional water treatments methods, for the past decades, researchers have been developing cost-effective ways of removing MC-LR from water bodies. This study reports the application of powdered activated carbon (PAC) obtained from the waste tyre for the removal of MC-LR. The choice of the adsorbent was chosen due to its attractive properties. The prepared tyre-based PAC was found to have the large surface area (1111 m² g^-1). The detection of MC-LR was achieved using high performance liquid chromatography (HPLC) coupled with a PDA detector. The experimental parameters (such as optimum pH, dosage and contact time) affecting the removal of MC-LR using tyre based-powdered activated carbon were optimized using response surface methodology (RSM). Maximum removal of MC-LR was achieved under the following optimum conditions; sample pH 4, carbon dosage concentration 10,000 mg L^-1 and contact time of 34 min. Under optimum conditions, kinetic studies and adsorption isotherms reflected better fit for pseudo-second-order rate and Langmuir isotherm model, respectively. The optimized method was applied for the removal of MC-LR in wastewater sample. The effluent and influent sample contained initial concentrations ranging from 0.52 to 8.54 μg L^-1 and the removal efficiency was 100%.

Layer-by-layer assembly and functionalization of nanobentonite with nanopolyaniline and oleic acid to remove divalent Zn, Co,65Zn, and 60Co from water and radioactive wastewater

A novel material was designed using layer-by-layer functionalization of nanobentonite with nanopolyaniline and oleic acid to produce an efficient NBent-NPA-OA nanosorbent to adsorb the divalent ionic Zn/Co and their radioisotopes ⁶⁵Zn/⁶⁰Co from tap water and radioactive wastewater. The new nanosorbent was characterized by Fourier-transform-infrared (FT-IR), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and determination of surface area. The NBent-NPA-OA particle size was ranged between 9.45 and 33.60nm according to HR-TEM analysis. The FT-IR exhibited several characteristic absorption peaks due to the existence of deposited layers of nanopolyaniline and oleic acid on the surface of nanobentonite surface. Different experimental parameters including, initial pH, contact time, nanosorbent, initial concentration of the target metals and interfering ions were varied, investigated and optimized to evaluate the removal efficiency of the divalent ionic Zn/Co from their solutions by the action of NBent-NPA-OA nanosorbent. The collected batch equilibrium results confirmed the efficiency of newly functionalized NBent-NPA-OA nanosorbent to uptake the divalent ionic Zn/Co from their solutions (10.0mL of 0.01mol/L) with maximum capacity values 2.916 and 1.960mmolg^-1, respectively using 5.0mg nanosorbent, pH 6.0 and 20min contact reaction time. The multistage microcolumn system was successfully implemented to remove the divalent ionic Zn/Co from tap water in addition to their radioisotopes ⁶⁵Zn/⁶⁰Co from radioactive wastewater. The current study refers to an excellent recovery and the removal percent of the radioisotopes ⁶⁵Zn (96.4) and ⁶⁰Co (92.7%) using NBent-NPA-OA nanosorbent.

Sonochemical synthesis of magnetic responsive Fe3O4@TMU-17-NH2 composite as sorbent for highly efficient ultrasonic-assisted denitrogenation of fossil fuel

In this work, a novel magnetic responsive composite was fabricated by encapsulation of Fe₃O₄ nanoparticles into an amino-functionalized MOF (TMU-17-NH₂) under ultrasound irradiation. The prepared materials were characterized by several techniques such as elemental analyses, PXRD, FT-IR, N₂ adsorption, TGA and ICP. This composite has been applied to the adsorptive removal of nitrogen-contain compounds in model liquid fuel. The prepared composite demonstrates very good performance for the removal of NCCs. The maximum adsorption capacity of IND and QUI over prepared composite calculated 375.93 and 310.18mg·g^-1 at 25°C, respectively. The composite material is magnetically separable and reusable for several times.

Adsorptive removal of bisphenol A (BPA) from aqueous solution: A review

Endocrine-disrupting compounds (EDCs) are an important class of emerging contaminants that have been detected (and are still being detected) in aquatic environments such as surface waters, groundwater, wastewater, runoff, and landfill leachates. Bisphenol A (BPA) is a known endocrine disruptor that is acutely toxic to the living organisms. BPA has been widely used in the manufacture of sunscreen lotions, nail polish, body wash/lotions, bar soaps, shampoo, conditioners, shaving creams, and face lotions/cleanser, besides its other industrial applications. In the present review, an overview of the recent research studies dealing with the BPA removal from water by adsorption method is presented. We have reviewed various conventional and non-conventional adsorbents which have been used for BPA removal from water. It is evident from the literature reviewed that modified adsorbents and composite materials have shown promising results for BPA removal from water. Literature has been extensively discussed in terms of adsorption capacities, fitted isotherm and kinetic models and thermodynamic aspects.

Adsorptive desulfurization and denitrogenation using metal-organic frameworks

With the increasing worldwide demand for energy, utilization of fossil fuels is increasing proportionally. Additionally, new and unconventional energy sources are also being utilized at an increasing rate day-by-day. These sources, along with some industrial processes, result in the exposal of several sulfur- and nitrogen-containing compounds (SCCs and NCCs, respectively) to the environment, and the exposure is one of the greatest environmental threats in the recent years. Although, several methods were established for the removal of these pollutants during the last few decades, recent advancements in adsorptive desulfurization and denitrogenation (ADS and ADN, respectively) with metal-organic frameworks (MOFs) make this the most promising and remarkable method. Therefore, many research groups are currently involved with ADS and ADN with MOFs, and the results are improving gradually by modifying the MOF adsorbents according to several specific adsorption mechanisms. In this review, ADS and ADN studies are thoroughly discussed for both liquid-phase and gas-phase adsorption. The MOF modification procedures, which are important for improved adsorption, are also described. To improve the knowledge among the scientific community, it is very important to understand the detailed chemistry and mechanism involved in a chemical process, which also creates the possibility and pathway for further developments in research and applications. Therefore, the mechanisms related to the adsorption procedures are also discussed in detail. From this review, it can be expected that the scientific community will obtain an understanding of the current state of ADS and ADN, their importance, and some encouragement and insight to take the research knowledge base to a higher level.

Adsorptive removal of fluoride from aqueous medium using a fixed bed column packed with Zr(IV) loaded dried orange juice residue

The potential of the adsorbent prepared from DOJR marketed as cattle food in Japan was identified as an efficient and low cost adsorbent for fluoride using fixed bed column. DOJR was loaded with Zr(IV) ions to develop active adsorption sites for fluoride. Fluoride adsorption performance of column packed with Zr(IV) loaded DOJR was assessed under variable operating conditions such as Zr(IV) loading temperature, initial fluoride concentration, bed depth, initial pH, and flow rate. Breakthrough curve modeling showed that Thomas and bed depth service time (BDST) models were in good agreement with the experimental data. Application of adsorbent investigated in this study to the treatment of actual waste plating solution containing fluoride ion showed successful removal below acceptable standard in Japan using a fixed bed column, hence, Zr(IV)-DOJR can be expected to be a promising candidate for the treatment waste water containing trace amount of fluoride ion in fixed bed column.