Cetylpyridinium bromide assisted micellar-enhanced ultrafiltration for treating enrofloxacin-laden water

Construction of attapulgite decorated cetylpyridinium bromide/cellulose acetate composite beads for removal of Cr (VI) ions with emphasis on mechanistic insights

Eco-friendly and renewable composite beads were constructed for efficient adsorptive removal of Cr (VI) ions. Attapulgite (ATP) clay decorated with cetylpyridinium bromide (CPBr) was impregnated into cellulose acetate (CA) beads, which were formulated through a simple and cost-effective solvent-exchange approach. FTIR, XRD, SEM, Zeta potential, and XPS characterization tools verified the successful formation of ATP-CPBr@CA beads. The composite beads displayed a spherical and porous shape with a positively charged surface (26.6 mV) at pH 2. In addition, higher adsorption performance was accomplished by ATP-CPBr@CA composite beads with ease of separation compared to their components. Meanwhile, equilibrium isotherms pointed out that the Langmuir model was optimal for describing the adsorption process of Cr (VI) with a maximal adsorption capacity of 302 mg/g. Moreover, the D-R isotherm model verified the physical adsorption process, while adsorption data obeyed the pseudo-second-order kinetic model. Further, XPS results hypothesized that the removal mechanism involves adsorption via electrostatic interactions, redox reaction, and co-precipitation. Interestingly, the ATP-CPBr@CA composite beads reserved tolerable adsorption characteristics with a maximum removal present exceeding 70% after reuse for seven successive cycles, proposing its feasible applicability as a reusable and easy-separable candidate for removing heavy metals from aquatic bodies.

Understanding the coordination behavior of antibiotics: Take tetracycline as an example

Gaining insight into the occurrence states of residual antibiotics is crucial to demystify their environmental behavior. However, the complexation of heteroatoms functioned on antibiotic molecules to metal ions in the water environment is not fully understood. This study reports that a fluorescence response was unexpectedly triggered by tetracycline (TC) and Al3+, serving as solid evidence to visualize the Al3+-TC coordination reaction. Differential electron absorption spectroscopy shows a quantifiable signal of the redshifted n-π* transition with a coordination reaction, which is also proportional to the fluorescence. The occurrence of Al3+-complexed TC also caused a split in retention time in liquid chromatogram. The TC ligands were re-released in the presence of stronger ligands competing for central Al3+. The complex ratio of Al3+-TC is confirmed to be 1:1 using Job's plot with a stability constant of 1.01 × 106. Quantum chemical computations coupled with Gibbs free energy analysis simulated the formation of octahedral Al3+-TC configuration through a spontaneous bidentate chelation. This study helps convey a broad consensus and opens a new door in the mechanistic study of metal-involved antibiotic transformation process, leading to a better understanding that can ultimately be essential to reach the final goal of alleviating the antibiotic crisis.

Ganzoury M, Zhang N, de Lannoy CF. Nanocomposite Polymeric Membranes for Organic Micropollutant Removal: A Critical Review

The prevalence of organic micropollutants (OMPs) and their persistence in water supplies have raised serious concerns for drinking water safety and public health. Conventional water treatment technologies, including adsorption and biological treatment, are known to be insufficient in treating OMPs and have demonstrated poor selectivity toward a wide range of OMPs. Pressure-driven membrane filtration has the potential to remove many OMPs detected in water with high selectivity as a membrane's molecular weight cutoff (MWCO), surface charge, and hydrophilicity can be easily tailored to a targeted OMP's size, charge and octanol-water partition coefficient (Kow). Over the past 10 years, polymeric (nano)composite microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) membranes have been extensively synthesized and studied for their ability to remove OMPs. This review discusses the fate and transport of emerging OMPs in water, an assessment of conventional membrane-based technologies (NF, reverse osmosis (RO), forward osmosis (FO), membrane distillation (MD) and UF membrane-based hybrid processes) for their removal, and a comparison to the state-of-the-art nanoenabled membranes with enhanced selectivity toward specific OMPs in water. Nanoenabled membranes for OMP treatment are further discussed with respect to their permeabilities, enhanced properties, limitations, and future improvements.

The role of freshwater sludge and its carbonaceous derivatives in the removal of lead, phosphorus and antibiotic enrofloxacin: Sorption characteristics and performance

Freshwater sludge (FS) produced from drinking water treatment plants is generally filter pressed and disposed in the landfill. However, FS could be potentially reused. In this study, FS were processed into biochar and hydrochar via pyrolysis and hydrothermal carbonization, respectively. The sorption characteristics/mechanisms of FS and its derivatives (biochar-B300, B500 and B700 and hydrochar-H140, H160, H180 and H200) for the removal of three typical pollutants (i.e., lead (Pb), phosphorus (P) and enrofloxacin (ENR)) found in swine wastewater were investigated using batch adsorption tests and microstructural analyses. It was found that Pb sorption was relatively enhanced due to the increased electrostatic attraction and surface precipitation of Pb(OH)₂ while the anionic phosphate adsorption relatively decreased as a result of enhanced electrostatic repulsion at higher solution pHs. Comparatively, ENR adsorption was less affected by solution pH probably due to dominance of physical adsorption evidenced by the good fitting of the BET isotherm model (R² = 0.95). The maximum sorption capacities of Pb were in the order of B700≈B500 (71 mg/g)>B300 ~ FS(37 mg/g)>H140 ~ H160 (13 mg/g)>H180 ~ H200 (6 mg/g). The adsorption capacities for P were relatively lower: FS (47 mg/g)>B300 (38 mg/g)>H140 (27 mg/g)>B700 (37 mg/g)≈B500 (24 mg/g)≈H160 (23 mg/g)>H180 (16 mg/g)>H200 (14 mg/g). This study provides an understanding of the sorption characteristics and mechanisms of FS and its carbonaceous products for common cationic, anionic and organic pollutants and elucidates new insights into the reuse of FS for pollutant removal to achieve the waste-to-resource concept and enhance water quality, soil health and food safety.

Modeling and multi-objective optimization of commercial ethylene oxide reactor to strike a delicate balance between profit and negative environmental impact

The present work emphasizes the development of a generic methodology that addresses the core issue of any running chemical plant, i.e., how to maintain a delicate balance between profit and environmental impact. Here, ethylene oxide (EO) production plant has been taken as a case study. The production of EO takes place in a multiphase catalytic reactor, the reliable first principle-based model of which is still not available in the literature. Artificial neural network (ANN) was therefore applied to develop a data-driven model of the complex reactor with the help of actual industrial data. The model successfully built up a correlation between the catalyst selectivity and other operational parameters. This model was used to establish two objective functions, profit and environmental impact. In this paper, the negative environmental impact has been designated by Eco-indicator 99, which considers all the negative health and environmental impacts of a certain product. A recently developed metaheuristic optimization technique, namely multi-objective firefly (MOF) algorithm, was used to develop Pareto diagram of profit vs. Eco-99. The Pareto diagram will help the plant engineers to make strategy on what operating conditions to be maintained to make a delicate balance between profit and environmental impact. It was also found that by applying this modeling and optimization technique, for a 130 kTA EO plant, approximately 7048 t/year of carbon dioxide can be saved from emission into the atmosphere.

Performance enhancement of commercial ethylene oxide reactor by artificial intelligence approach

The present work emphasizes the development of a generic methodology that addresses the core issue of any running chemical plant, i.e., how to maintain a delicate balance between profit and environmental impact. Here, an ethylene oxide (EO) production plant has been taken as a case study. The production of EO takes place in a multiphase catalytic reactor, the reliable first principle-based model of which is still not available in the literature. Artificial neural network (ANN) was therefore applied to develop a data-driven model of the complex reactor with the help of actual industrial data. The model successfully built up a correlation between the catalyst selectivity and temperature with other operational parameters. A hybrid multi-objective metaheuristic optimization technique, namely ANN-multi-objective genetic algorithm (MOGA) algorithm was used to develop a Pareto diagram of selectivity versus reactor temperature. The Pareto diagram will help the plant engineers to make a strategy on what operating conditions to be maintained to make a delicate balance between profit and environmental impact. It was also found that by applying this hybrid ANN-MOGA modeling and optimization technique, for a 720 KTA ethylene glycol plant, approximately 32,345 ton/year of carbon-di-oxide emission into the atmosphere can be reduced. Along with the reduction of environmental impact, this hybrid approach enables the plant to reduce raw material cost of nine million USD per annum simultaneously.

Advances in micro interfacial phenomena of adsorptive micellar flocculation: Principles and application for water treatment

Among various aqua remediation technologies, separation aims at cleaning pollutants by isolating them despite their destruction; solutes can also be recovered after the process. Adsorptive micellar flocculation (AMF) has been known as an important surfactant-based technique to separate poorly water-soluble hazardous pollutants from aqua media as an efficient and energy-intensive replacement for other surfactant-based techniques, as such AMF should be known. AMF is based on the partitioning of solutes gradient from bulk solution into the nanosized smart anionic surfactant micelle followed by flocculation. However, unlike coagulation/flocculation or adsorption, AMF is not viable for the production of drinking water in water utilities due to the loss of surfactant monomers. Unfortunately, it can be used as a reservoir or for the recycling/recovery of organic pollutants (intermediates) (ions, organics/bioactive, dyes, etc.), even at high concentrations. The performance of AMF depends on various parameters, and this review briefly summarizes the existing researches on different pollutants removal by AMF and material recovery/recycling. This includes operating condition factors (surfactants, flocculants, surfactant-flocculant or surfactant-pollutant concentration ratio, and water conditions chemistry). Because varieties of micro interfacial phenomena other than physical interactions occur in a versatile micellar environment in the AMF process, emphases are given to adsorptive oxidation, micellar catalysis, selectivity. Furthermore, for the first time, this review gives an overview of understanding the state-of-the-art multifunctional nano amphiphile-based AMF that behaves mimetic to aquatic organisms in the process of pollutant removal. The efficiency of AMF, including recycling concentrated solution without noticeable deterioration, as an auxiliary resource/income for the next cycle, signifies economic viability, versatility, and manifold applications in aqua remediation. Significance, ways to achieve enhanced process efficiency, as well as challenges and future opportunities in wastewater treatment, are also highlighted.

Theoretical study on charge distribution in cetylpyridinium cationic surfactant

Here, we report the electrostatic potential maxima and partial atomic charges evaluated on cetylpyridinium cation. The Hartree-Fock method and six DFT functionals (namely, PBE, TPSS, B3LYP, PBE0, M06, and wB97) were used to calculate partial atomic charges via CHELPG, Mulliken, Löwdin, Hirshfeld, and natural population schemes. Calculations were performed for the gas phase and for the CPCM water solvated cation, resulting in a set of 70 types of partial atomic charges. The main tendencies in charge deviations were discussed. In comparison with the electrostatic potential-based CHELPG partial charges, Hirshfeld, Mulliken, Löwdin, and NPA partitioning schema lead to an almost steady decrease in the partial charges in the cetyl chain. This agreed closely with the redistribution of electrostatic potential mapped onto the 0.002 e/Bohr³ isodensity surface.

Removal of cadmium from wastewater by magnetic zeolite synthesized from natural, low-grade molybdenum

Zeolite has a high adsorption capacity for heavy metals, but it is difficult to separate from the medium because of its small particle size. In this study, magnetic zeolite was synthesized from natural, low-grade molybdenum ore by adding nano ferroferric oxide (saturation magnetization 83.43 emu/g) directly in the hydrothermal synthesis process, which was used to adsorb cadmium from wastewater. The results of scanning electron microscopy showed that the nano ferroferric oxide was adhered to the surface of the zeolite to make it magnetic. The vibrating sample magnetometer showed that the larger the amount of nano ferroferric oxide added, the higher the saturation magnetization of the magnetic zeolite. The saturation magnetization of the magnetic zeolite with a loading proportion of 25% was 18.18 emu/g with a specific surface area of 459.8 m²/g. The adsorption experiments showed that when the pH value is greater than 4, the adsorption capacity of magnetic zeolite is high and stable, and the theoretical maximum adsorption capacity is 204.2 mg Cd/g. Na⁺ and Ca²⁺ have different inhibitory functions on the adsorption capacity. The mapping graphs showed that cadmium is captured by the magnetic zeolite after contact with cadmium, and XRD confirmed the presence of cadmium oxide in the magnetic zeolite after adsorption, XPS and EDS results indicated that ion exchange is one of the main mechanisms of cadmium adsorption by magnetic zeolites, and electrostatic adsorption may also have a contribution.

The biosorptive uptake of enrofloxacin from synthetically produced contaminated water by tamarind seed derived activated carbon

The veterinary antibiotic enrofloxacin (ENR), an emerging contaminant, poses great concern due to its ubiquitous nature.