The role of kaolin and kaolin/ZnO nanoadsorbents in adsorption studies for tannery wastewater treatment

Modeling sustainable photocatalytic degradation of acidic dyes using Jordanian nano-Kaolin-TiO2 and solar energy: Synergetic mechanistic insights

The abstract highlights the global issue of environmental contamination caused by organic compounds and the exploration of various methods for its resolution. One such approach involves the utilization of titanium dioxide (TiO2) as a photocatalyst in conjunction with natural adsorption materials like kaolin. The study employed a modeling-based approach to investigate the sustainable photocatalytic degradation of acidic dyes using a Jordanian nano-kaolin-TiO2 composite material and solar energy. Mechanistic insights were gained through the identification of the dominant reactive oxygen species (ROS) involved in the degradation process, as well as the synergetic effect between adsorption and photocatalysis. The Jordanian nano-kaolin-TiO2 composite was synthesized using the sol-gel method and characterized. The nanocomposite photocatalyst exhibited particle sizes ranging from 27 to 41 nm, with the TiO2 nanoparticles well-dispersed within the kaolin matrix. The efficacy of this nanocomposite in removing Congo-red dye was investigated under various conditions, including pH, initial dye concentration, and photocatalyst amount. The optimal conditions for dye removal were found to be at pH 5, with an initial dye concentration of 20 ppm, and using 0.1 g of photocatalyst, resulting in a 95 % removal efficiency. The mechanistic insights gained from this study indicate that the hydroxyl radicals (•OH) generated during the photocatalytic process play a dominant role in the degradation of the acidic dye. Furthermore, the synergetic effect between the adsorption of the dye molecules onto the photocatalyst surface and the subsequent photocatalytic degradation by the ROS was found to enhance the overall removal efficiency. These findings contribute to the fundamental understanding of the photodegradation mechanisms and guide the development of more efficient photocatalytic systems for the treatment of acidic dye-containing wastewater. The use of solar power during the purification procedure also leads to cost reduction and strengthens sustainability efforts.

Bioinspired hierarchical and dual-morphology humic-acid/pectin/chitosan composite aerogels for efficient removal of pollutants from wastewater

How to solve the contradiction between the efficiency and adsorption rate of porous materials in adsorbing pollutants has always been one of the focus issues. In this study, the small landscape cypress trees structure like biomimetic of a hierarchical and dual morphology 3D porous HA-based aerogel was designed and synthesized to use humic acid (HA), pectin (PE) and chitosan (CTS) as raw materials, which it was formed by the disorderly overlapping of lamella composed of fiber networks in 3D space. Due to its special microstructure, it can be used like separation membrane, which allowing for rapid adsorption of pollutants in the water while the water flow passes through quick. In general, this work provides a new concept for owning fast adsorption rate and efficient adsorption of porous materials of preparation to use green method.

Hyphenated Fenton-column packed nMnO-modified wood biochar for tannery effluent treatment: Adsorption mechanism and reusability study

Industrial wastewater contains a wide range of pollutants that, if released directly into natural ecosystems, have the potential to pose serious risks to the environment.This study aims to investigate sustainable and efficient approaches for treating tannery wastewater, employing a combination of hyphenated Fenton oxidation and adsorption processes. Rigorous analyses were conducted on wastewater samples, evaluating parameters like COD, sulphide, NH3-N, PO43-, NO3-, and Cr(VI). The performance of this adsorbent material was gauged through column adsorption experiments. A comprehensive characterization of the adsorbent was undertaken using techniques such as SEM, EDX, BET, FTIR, XRD, and LIBS. The study delved into varying operational parameters like bed depth (ranging from 3.5 to 9.5 cm) diameter (2.5 cm) and influent flow rate (ranging from 5 to 15mLmin-1). The experimental outcomes revealed that increasing the bed depth and decreasing the influent flow rate significantly bolstered the adsorption column's effectiveness. Breakthrough curves obtained were fitted with different models, including the Thomas and Yoon-Nelson models. The most optimal column performance was achieved with a bed height of 10.5 cm and a flow rate of 5mLmin-1. The combined process achieved removal efficiencies of 94.5% for COD, 97.4% for sulphide, 96.2% for NH3-N, 83.1% for NO3-, 79.3% for PO43-, and 96.9% for Cr(VI) in tannery effluent. This research presents a notable stride toward the development of sustainable and efficient strategies for tannery wastewater treatment.

Constructing the synergistic effects of chitosan and ionic liquid on SPEEK polymer for efficient adsorption of crystal violet dye

In the study, a novel chitosan biopolymer and 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid (IL)-incorporated sulfonated poly (ether ether ketone) (SPEEK) composite (Ch-IL@SPEEK) was prepared for adsorption of cationic crystal violet (CV) dye. The proposed composite was well characterized by several techniques. CV adsorption performance was examined via batch studies by varying various variables involving adsorbent dosage, contact time pH and temperature. The isotherm results were demonstrated the adsorption characters of the processes were Langmuirian. The maximum adsorption capacity was determined as 77.66 mg g-1 for the composite which was significantly higher than SPEEK (qmax = 45.36 mg g-1). The determined equilibrium time of the operated system was 360 min and the kinetic model was assessed as Elovich. At low pHs the protonated surface groups repelled the positively charged CV and the adsorption rate increased with increasing pH. The process is spontaneous and favorable as it proceeds via endothermic interactions. Furthermore, even at the end of 5 successful adsorption cycles, 77.86 % CV removal was obtained. Remarkable efficiencies were also achieved in the removal performance of different organic pollutants. Based on the reported results, Ch-IL@SPEEK composite were exhibited as an impressive adsorbent material for adsorption processes.

A novel approach for the facile synthesis of zinc oxide/carbon hybrid systems from corn distillers soluble: Surface modification and characterization for sustainable remediation

Sustainable, efficient, and environmentally friendly ways to tailor the carbonaceous materials from bio sources with desired functionalities remain a challenge around the world. In this study, we represent a novel approach to synthesize carbon hybrid material based on Zinc Oxide/carbon (ZnO/C) hybrid systems by catalytic hydrothermal process via crosslinking reaction through nucleation and growth of ZnO particles at the functional groups of oxidized carbon material. This research explored the volarization of Condensed Corn Distillers Soluble (CDS) as a carbon precursor to synthesize biobased carbon spheres. Surface modification of the produced carbon spheres took place using zinc chloride (ZnCl2) during hydrothermal carbonization (HTC). Zinc chloride (ZnCl2) was used to function as a catalyst during HTC and functioned as a ZnO source to synthesize (ZnO/C) hybrid systems. Design Expert software v13 was used to design the hydrothermal carbonization (HTC) experiments and response surface methodology was used to find the optimized conditions for the preparation of carbon hybrid systems. The hydrothermal synthesis process introduced 3D stone like zinc oxide particles onto the carbon matrix. These particles were self-assembled onto the carbon framework to produce carbon hybrid systems with unique physical, chemical, structural and functional properties. Herein, the obtained carbon hybrid systems (ZnO/C) were investigated and discussed in detail. ZnO/C hybrid systems were analyzed for surface morphology using scanning electron microscopy (SEM) that presented a 3D spherical interconnected phase and XRD analyses were used for phase crystallinity that showed new crystalline phases such as hopeite and zincite after the ZnCl2 incorporation. Surface functional groups were also analyzed by FTIR and results confirmed the presence of hydrophilic groups such as -OH, CC, and COOH on the surface of ZnO/C hybrid carbon systems. This study provided the insightful guidance for tailoring novel design of multifunctional carbon material as an adsorbent/catalyst for various applications of sustainable remediation.

Heavy metals immobilization and bioavailability in multi-metal contaminated soil under ryegrass cultivation as affected by ZnO and MnO2 nanoparticle-modified biochar

Pollution by heavy metals (HMs) has become a global problem for agriculture and the environment. In this study, the effects of pristine biochar and biochar modified with manganese dioxide (BC@MnO2) and zinc oxide (BC@ZnO) nanoparticles on the immobilization and bioavailability of Pb, Cd, Zn, and Ni in soil under ryegrass (Lolium perenne L.) cultivation were investigated. The results of SEM-EDX, FTIR, and XRD showed that ZnO and MnO2 nanoparticles were successfully loaded onto biochar. The results showed that BC, BC@MnO2 and BC@ZnO treatments significantly increased shoots and roots dry weight of ryegrass compared to the control. The maximum dry weight of root and shoot (1.365 g pot-1 and 4.163 g pot-1, respectively) was reached at 1% BC@MnO2. The HMs uptake by ryegrass roots and shoots decreased significantly after addition of amendments. The lowest Pb, Cd, Zn and Ni uptake in the plant shoot (13.176, 24.92, 32.407, and 53.88 µg pot-1, respectively) was obtained in the 1% BC@MnO2 treatment. Modified biochar was more successful in reducing HMs uptake by ryegrass and improving plant growth than pristine biochar and can therefore be used as an efficient and cost effective amendment for the remediation of HMs contaminated soils. The lowest HMs translocation (TF) and bioconcentration factors were related to the 1% BC@MnO2 treatment. Therefore, BC@MnO2 was the most successful treatment for HMs immobilization in soil. Also, a comparison of the TF values of plant showed that ryegrass had a good ability to accumulate all studied HMs in its roots, and it is a suitable plant for HMs phytostabilization.

Recent advances in the application of clay-containing hydrogels for hemostasis and wound healing

INTRODUCTION

Immediate control of bleeding and anti-infection play important roles in wound management. Multiple organ dysfunction syndrome and death may occur if persistent bleeding, hemodynamic instability, and hypoxemia are not addressed. The combination of clay and hydrogel provides a new outlet for wound hemostasis. In this review, the current research progress of hydrogel/clay composite hemostatic agents was reviewed.

AREAS COVERED

This paper summarizes the characteristics of several kinds of clay including kaolinite, montmorillonite, laponite, sepiolite, and palygorskite. The advantages and disadvantages of its application in hemostasis were also summarized. Future directions for the application of hydrogel/clay composite hemostatic agents are presented.

EXPERT OPINION

Clay can activate the endogenous hemostatic pathway by increasing blood cell concentration and promoting plasma absorption to accelerate the hemostasis. Clay is antimicrobial due to the slow release of metal ions and has a rich surface charge with a high affinity for proteins and cells to promote tissue repair. Hydrogels have some properties such as good biocompatibility, strong adhesion, high stretchability, and good self-healing. Despite promising advances, hydrogel/clay composite hemostasis remains a limitation. Therefore, more evidence is needed to further elucidate the risk factors and therapeutic effects of hydrogel/clay in hemostasis and wound healing.

Preparation of novel clay/chitosan/ZnO bio-composite as an efficient adsorbent for tannery wastewater treatment

This study focuses on the preparation of an activated clay/chitosan/ZnO bio-composite using solvent casting method. Clay was activated through microwave radiation using 1 M H2SO4 at a minimum liquid to solid ratio (L/S). Chitosan was extracted from waste prawn shell and ZnO nanoparticles (ZnO-NPs) were synthesized from zinc acetate di-hydrate (Zn (CH3CO2)2·2H2O) using the sol-gel method. The produced bio-composite were characterized using FT-IR, TGA, XRD and SEM. Response surface methodology (RSM) was used for experimental design to find out the optimum conditions, e.g., pH of the solution, dosage of adsorbent and contact time for the removal of methylene blue (MB) and Cr (VI) using MINITAB 18.1 software. The optimum conditions obtained for the highest removal of MB were pH 9.57, dosage 55.44 mg and contact time 114.09 min. Similarly, for the highest removal of Cr (VI) the optimum conditions were pH 3.75, dosage 67.42 mg and contact time 111.27 min. Applying these optimum conditions, the highest removal efficiency for MB and Cr (VI) was obtained at 84.21 % and 82.67 % with 9.57 mg g-1 and 10.45 mg g-1 of adsorption capacity respectively. The adsorption data were studied for both Langmuir and Freundlich isotherm. The value of maximum Langmuir sorption was (qm) 17.346 mg g-1 and 17.621 mg g-1 for MB and Cr (VI) respectively.

Efficient photodegradation of methyl red dye by kaolin clay supported zinc oxide nanoparticles with their antibacterial and antioxidant activities

Kaolin clay-supported Zinc oxide (ZnO/KC) and ZnO NPs nanoparticles (NPs) were prepared by a chemical reduction process and used for the photodegradation of methyl red (MR) dye as a photocatalyst. Due to the interlayered porous structure of the KC, we achieved an extremely good association between ZnO NPs and KC. The product confirmation was conducted by Scanning electron microscopy (SEM), X-Ray diffraction (XRD), energy dispersive X-Ray (EDX), and Fourier transforms infrared (FTIR). SEM showed the irregular morphology of ZnO NPs, while ZnO/KC NCs were predominately round-shaped. Moreover, in both cases, NPs were present in both dispersed as well as agglomerated forms with an average particle size below 100 nm. The results acquired from photodegradation analyses show that ZnO NPs and ZnO/KC NCs degraded about 90 and 99% of MR dye respectively, under UV light in a short irradiation time of 10 min. The recovered and re-recovered ZnO NPs and ZnO/KC NCs also considerably photodegraded MR dye in an aqueous medium. The same NPs also exhibit promising bioactivities against two pathogenic bacteria, i.e., Citrobacter and Providencia. The antioxidant activity of ZnO/KC NCs reached to reasonable 70% compared to the 88% activity of the standard ascorbic acid.

Cocoyam powder extracted from Colocasia antiquorum as a novel plant-based bioflocculant for industrial wastewater treatment: Flocculation performance and mechanism

In the current investigation, the comparative study of cocoyam bioflocculant (CYBF) and chemical flocculant for the removal of heavy metals, COD, BOD, TDS, TSS, sulphate and nitrate from tannery effluent, and dyes from synthetic dye wastewater were examined. Different analytical techniques, including Fourier transforms infrared (FTIR), X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDX), were used to characterise the extracted bioflocculant. FTIR spectral measurement of the bioflocculant demonstrated the presence of hydroxyl, carboxyl, and amino groups. By using bioflocculant, the highest removal of TSS (85.5%), TDS (76.2%), BOD (74%), COD (50.5%), sulphate (54.4%), nitrate (52%), Lead (65%), Chromium (60%), Nickel (57.9%), from tannery effluent was achieved at pH 6 and bioflocculant dosage of 8 mg/L. While, 80% congo red, 79% methyl orange, 73% safranin, and 72% methylene blue were removed from synthetic dye wastewater by cocoyam bioflocculant. Two flocculation mechanisms were found for dye removal, electrostatic force of attraction, and hydrogen bonding. In the case of metal adsorption, only electrostatic interactions were observed between metal ions and functional groups of bioflocculant. The cocoyam bioflocculant exhibited excellent flocculation efficacy and thus can be used in wastewater treatment to remove heavy metals and other pollutants.

Mathematical modeling and statistical approach in tannery wastewater treatment

The present work investigated the feasibility of photo-oxidation process for the removal of oil and chemical oxygen demand (COD) in Indian tannery wastewater with the support of mathematical modeling and statistical approach. The influence of process variables such as nano-catalyst dose and reaction time was analyzed on the removal of oil/grease and COD. The obtained results are discussed using the response surface methodology (RSM) design in detail. Zinc oxide nanoparticles prepared from Eclipta prostrata plant leaves and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX), and transmission electron microscopy (TEM). COD removal of 93.6% and oil and grease removal of 90% in 35 min using 3 mg/L nanoparticle dosage were recommended as an optimum condition in photo-oxidation process. PRACTITIONER POINTS: The structure and surface morphology of zinc oxide nanoparticles in spherical shape was confirmed by the SEM with EDX and XRD analysis. Response surface methodology (RSM) with Box-Behnken design (BBD) combination was explained the effect of different parameters on COD and oil and grease removal. The treatment of photo-oxidation process showed chemical oxygen demand (COD) removal of 93.6% and coil and grease removal of 90% in 35 min using mg/L nanoparticle dosage. The obtained result showed that photo oxidation of green synthesized zinc oxide nanocatalyst was found to be an effective method for tannery wastewater.

Bioinspired Interfacial Spontaneous Growth of ZnO Nanocatalysts onto Recycled Textiles as a Sustainable Approach for Water Purification

Zinc oxide, as a commonly used photocatalytic degradation of organic pollutants, typically shows limitations in wastewater treatment, such as aggregation and recycling problems caused by nanoscale dimensions and inappropriate substrates. Anchoring ZnO on substrates is a strategy to obtain stable catalytic performance. Particularly, natural fibers with hollow structures are an attractive alternative for ecological and economical ZnO loading templates, but depositing ZnO onto hollowed fiber surfaces presents a challenge. Here, a straightforward in situ growth method for producing nanostructured zinc oxide on cotton fibers from recycled garments is reported. The modified polydopamine on the fiber surface captures the catalyst required for in situ growth of ZnO and serves as a platform for spontaneous catalytic crystal growth on the fiber surface. The ZnO nanocrystals are uniformly dispersed on the outer and inner walls of cotton fibers, demonstrating excellent durability in wastewater treatments. Moreover, the photocatalytic performance of functional fibers is optimized by doping Ag nanoparticles to improve degradation efficiency. This can extend the prospect of further applications of developed ZnO/fibers in optoelectronics, spintronics, and provide inspiration for recycling and upgrading of used garments.

Synthesis of copper-silver-zinc oxide nanocomposites for 4-nitrophenol reduction: doping and heterojunction

The charge transfer and visible-light absorption capacities of stable materials are crucial in several applications, such as catalysis, absorption, sensors, and bioremediation. Copper-silver-zinc oxide nanocomposites (NCs) were synthesized using PVA as a capping agent and urea as a stabilizing agent. DTG analysis confirmed 500 °C was the optimum temperature for the total decomposition of PVA after capping the nanoparticles (NPs) to yield a pure composite. The XRD analysis showed the presence of copper inclusions in the ZnO lattice and the formation of Ag and CuO heterojunctions with ZnO. The photoluminescence (PL) analysis confirmed the more significant visible light absorption and charge transfer properties of the composite compared to those of single ZnO NPs. Foam-type porosity occurred during gas evolution at many of the points shown in the SEM/TEM images. Slight lattice fringe differences between the composite and ZnO NPs due to copper inclusion were confirmed from the HRTEM image and XRD pattern analysis. The crystallinity of the NPs and NCs was confirmed by the XRD pattern and SAED analysis. The diffusion-controlled charge transfer process was witnessed through CV electrochemical analysis. Thus, the energy- and time-efficient solution combustion synthesis (SCS) approach has a crucial future outlook, specifically for an industrial, scalable application. The NCs demonstrated more potential than ZnO NPs in an organic catalytic reduction reaction of 4-nitrophenol to 4-aminophenol.

Optimization and Modeling of Cr (VI) Removal from Tannery Wastewater onto Activated Carbon Prepared from Coffee Husk and Sulfuric Acid (H2SO4) as Activating Agent by Using Central Composite Design (CCD)

The primary goal of this research is to lower the hexavalent chromium (Cr (VI)) concentration that has occurred from the growth of the tannery industry. As a result, the potential for heavy metal concentration is increasing day by day. Industrial effluent containing Cr (VI) contributes significantly to water pollution. Chromium hexavalent ion (Cr (VI)) in wastewater is extremely hazardous to the environment. It is critical to address such a condition using activated carbon derived from biomass. Adsorption is one of the most successful methods for removing hexavalent chromium from wastewater. Treated wastewater has no substantial environmental contamination consequences. The ash content, moisture content, volatile matter content, and fixed carbon content of wet coffee husk were 3.51, 10.85, 68.33, and 17.31, respectively. The physicochemical properties of coffee husk-based activated carbon (CHBAC) obtained during experimentation were pH, porosity, the yield of CHBAC, bulk density, point of zero charges, and specific surface area of 5.2, 58.4 percent, 60.1 percent, 0.71 g/mL, 4.19, and 1396 m2/g, respectively, indicating that CHBAC has a higher capacity as an adsorbent medium. For optimization purposes, the parameters ranged from pH (0.3–3.7), dose (2.3–5.7) $g$ , and contact time (0.3–3.7) hr. The quadratic models were chosen for optimization, and the $p$ value for the model was significant since it was less than 0.05, but the lack of fit model was inconsequential because it was more than 0.05. The optimum adsorption obtained with numerical optimization of Cr (VI) was 97.65 percent. This was obtained at a pH of 1.926, a dose of 4.209 g/L, and a contact time of 2.101 hours. This result was observed at a pH of 1.93, a dosage of 4.2 g/L, and a contact duration of 2.1 hours. The desirability obtained during numerical optimization was 1. Coffee husk-based activated carbon has a bigger surface area, and it has a stronger ability to absorb hexavalent chromium from tannery wastewater effluents.

Cerium-Bismuth Oxides/Oxynitrates with Low Toxicity for the Removal and Degradation of Organophosphates and Bisphenols

Nanoscale cerium-bismuth oxides/oxynitrates were prepared by a scalable low-temperature method at ambient pressure using water as the sole solvent. Solid solutions were formed up to a 1:1 Ce/Bi molar ratio, while at higher doping levels, bismuth oxynitrate photocatalysts with a pronounced layered structure were formed. Bismuth caused significant changes in the structure and surface properties of nanoceria, such as the formation of defects, oxygen-containing surface groups, and Lewis and Brønsted acid sites. The prepared bifunctional adsorbents/photocatalysts were efficient in the removal of toxic organophosphate (methyl paraoxon) from water by reactive adsorption followed by photocatalytic decomposition of the parent compound and its degradation product (p-nitrophenol). Bi-doped ceria also effectively adsorbed and photodegraded the endocrine disruptors bisphenols A and S and outperformed pure ceria and the P25 photocatalyst in terms of efficiency, durability, and long-term stability. The very low toxicity of Bi-nanoceria to mammalian cells, aquatic organisms, and bacteria has been demonstrated by comprehensive in vivo/in vitro testing, which, in addition to its simple "green" synthesis, high activity, and durability, makes Bi-doped ceria promising for safe use in abatement of toxic chemicals.

Quantitative Analysis of the Research Development Status and Trends of Tannery Wastewater Treatment Technology

In order to better grasp the development and trends of tannery wastewater (TWW) treatment research, this paper provides a review of the TWW treatment research dynamics based on the Web of Science (WoS) database and using CiteSpace software. The research dynamics, hot topics, evolutionary history and research trends in this field are revealed. The results showed that research related to TWW treatment has shown a high growth trend in the number of articles in recent years, and India was outstanding in terms of influence in this area. The keyword clustering analysis showed that the main research hotspots in the field of TWW treatment were biological treatment processes (phytoremediation, constructed wetlands, anaerobic treatment and biofilm reactors) and chemical treatment processes (coagulation and flocculation, and advanced oxidation processes). The analysis of new research frontiers showed that the bioremediation and the application of biofuel cells in TWW will become important research directions in the future.

Fe3O4/Mn3O4/ZnO-rGO hybrid quaternary nano-catalyst for effective treatment of tannery wastewater with the heterogeneous electro-Fenton process: Process optimization

This study investigated chemical oxygen demand (COD) removal from tannery wastewater (TWW) with a novel Fe₃O₄/Mn₃O₄/ZnO-rGO heterogeneous electro Fenton (HEF) hybrid magnetically-separable nano-catalyst. The graphite cathode and Ti/IrO₂/RuO₂ anode were used in the HEF process. With aeration (2 L/min), in-situ H₂O₂ generation occurred. The nano-catalyst was characterized by XRD, XPS, DLS, FT-IR, ζ potential, SEM, TEM, and BET techniques in detail. The system was modelled with a central composite design and optimized numerically. The established model was adequate, valid, reliable, and reproducible to predict the COD removal efficiency. OH and O₂^- were the oxidative species responsible for organic matter degradation. The effect of different processes was investigated, and efficiency was ranked from high to low as; HEF > anodic oxidation-H₂O₂ > anodic oxidation > adsorption. Under the optimum conditions; pH: 3.5, current density: 7.37 mA/cm², reaction time: 79.43 min, and catalyst dose: 0.06 g/L, COD removal efficiency reached a maximum of 97.08%. The energy consumption and cost to remove 1 kg COD were 10.87 kWh and $1.41. The degradation of COD fitted the pseudo-first-order model. The nano-catalyst was stable and reusable with a minimum yield of 78.12% after 5 cycles.

Experimental and modeling studies of the effects of nanoclay on the oil behaviors in a water-sand system

When oil is released into the oceans, spilled oil may get to the shoreline driven by wind and wave. This study comprehensively explored the effects of bentonite nanoclay on the oil behaviors in a water-sand system from both experimental and modeling perspectives. Four factors including nanoclay concentration, temperature, salinity, and pH have been studied. The increasing nanoclay concentration resulted in the decrease in remaining oil on sand. Higher temperature and salinity were associated with less residual oil on sand in the presence of nanoclay. The lower residual oil on sand with coexisting nanoclay was found to be at pH 7. The factorial analysis results indicated that the nanoclay concentration showed the most significant impact among these factors. Miscibility modeling results showed an increasing temperature was favorable to the nanoclay miscibility. Moreover, the effect of nanoclay on oil behavior was further revealed through the dynamic simulation, in which it can be seen the nanoclay could penetrate into oil droplets and promote the oil detachment from solid substrate. The results of this study can help understand the role of fine particles in the fate and transport of oil on shoreline and support the risk assessment and response planning after oil spill.

Adsorptive behavior of thallium using Fe3O4-kaolin composite synthesized by a room temperature ferrite process

Thallium (Tl) contaminants pose serious threats to the ecological environment and human health due to its acute/chronic poisoning on the health of most organisms even at low concentrations. To find a rapid and efficient technology in removing Tl from waters thus becomes a crucial issue. A magnetic Fe₃O₄-kaolin composite (denoted by FKC) with high specific surface area (133.7 m²/g) was successfully synthesized via a simple and low-cost technique for Tl(I) removing from various water media. The HRTEM images confirmed the existence of lattice fingers Fe₃O₄ and displayed that a large number of Fe₃O₄ nanoparticles dispersed on the surface of kaolin sheets. Compared with kaolin or Fe₃O₄ alone, FKC enhanced obviously the adsorption rate and capacity of Tl(I) over a wide pH range (4.5-9.0). The maximum adsorption capacity of FKC for Tl(I) was 19,347 mg/kg (calculated by Langmuir model), which was almost one hundred times and two times higher than those of kaolin and Fe₃O₄, respectively. Importantly, FKC was observed to have a great potential in removing Tl(I) from surface water, groundwater, and tap water in more alkaline conditions. By applying the external magnetic field, FKC could be recovered efficiently (99%) and rapidly (20 s). Moreover, Tl L₃-edge XANES spectra revealed that Tl(I) was adsorbed on the FKC and would not be converted to more toxic Tl(III). The cations (CaCl₂, NaCl, and KCl) and the ionic strength with concentrations of 0.001-1.0 mol/L showed a great influence on the adsorption of Tl(I) by FKC, implying that this adsorption was dominated by outer-sphere surface complexation at investigated pH values. The information provided is essential for designing a rapid and effective scavenger for removing Tl in various natural waters.

A critical review on the role of abiotic factors on the transformation, environmental identity and toxicity of engineered nanomaterials in aquatic environment

Engineered nanomaterials (ENMs) are at the forefront of many technological breakthroughs in science and engineering. The extensive use of ENMs in several consumer products has resulted in their release to the aquatic environment. ENMs entering the aquatic ecosystem undergo a dynamic transformation as they interact with organic and inorganic constituents present in aquatic environment, specifically abiotic factors such as NOM and clay minerals, and attain an environmental identity. Thus, a greater understanding of ENM-abiotic factors interactions is required for an improved risk assessment and sustainable management of ENMs contamination in the aquatic environment. This review integrates fundamental aspects of ENMs transformation in aquatic environment as impacted by abiotic factors, and delineates the recent advances in bioavailability and ecotoxicity of ENMs in relation to risk assessment for ENMs-contaminated aquatic ecosystem. It specifically discusses the mechanism of transformation of different ENMs (metals, metal oxides and carbon based nanomaterials) following their interaction with the two most common abiotic factors NOM and clay minerals present within the aquatic ecosystem. The review critically discusses the impact of these mechanisms on the altered ecotoxicity of ENMs including the impact of such transformation at the genomic level. Finally, it identifies the gaps in our current understanding of the role of abiotic factors on the transformation of ENMs and paves the way for the future research areas.

Adsorption of CO2 on In Situ Functionalized Straw Burning Ashes. An Innovative, Circular Economy-Based Concept for Limitation of Industrial-Scale Greenhouse Gas Emission

A new, innovative approach in the search for an effective and cheap carbon dioxide sorbent, in line with the circular economy and sustainable development principles, directs the attention of researchers to various types of waste ashes generated as a result of biomass combustion. In addition to the use of environmentally safe materials that have been experimentally identified, and that, in some way, have adjustable sorption capacity, it is also possible to rationally develop a widely applicable, simple, and inexpensive technology based on large amounts of this type of post-industrial waste, which is also an equally important issue for the natural environment (reducing the need for ash storage and accumulation). Even the lower sorption capacity can be successfully compensated for by their common availability and very low cost. Thus, the CO2 adsorption capability of the ashes from the combustion of straw biomass was experimentally investigated with the use of a high-pressure adsorption stand. The presented original technological concept has been positively verified on a laboratory scale, thus a functionalization-based approach to the combustion of substrate mixtures with nano-structural additives (raw, dried, calcined halloysite, kaolinite), introduced to improve the performance of straw biomass combustion and bottom ash formation in power boilers, clearly increased the CO2 adsorption capacity of the modified ashes. This allows for an advantageous synergy effect in the extra side-production of useful adsorbents in the closed-loop “cascade” scheme of the CE process. The addition of 4 wt.% kaolinite to straw biomass caused an over 2.5-fold increase in the CO2 adsorption capacity in relation to ash from the combustion of pure straw biomass (with a CO2 adsorption capacity of 0.132 mmol/g). In the case of addition of 4 wt.% nano-structured species to the straw combustion process, the best effects (ash adsorption capacity) were obtained in the following order: kaolinite (0.321 mmol/g), raw halloysite (0.310 mmol/g), calcined halloysite (0.298 mmol/g), and dried halloysite (0.288 mmol/g). Increasing the dose (in relation to all four tested substances) of the straw biomass additive from 2 to 4 wt.%, not only increase the adsorption capacity of the obtained ash, thus enriched with nano-structural additives, but also a showed a significant reduction in the differences between the maximum adsorption capacity of each ash is observed. The experimental results were analyzed using five models of adsorption isotherms: Freundlich, Langmuir, Jovanović, Temkin, and Hill. Moreover, selected samples of each ash were subjected to porosimetry tests and identification of the surface morphology (SEM). The obtained results can be used in the design of PSA processes or as permanent CO2 adsorbents, based on the environmentally beneficial option of using ashes from biomass combustion with appropriately selected additives.

In-Depth Study of Heavy Metal Removal by an Etidronic Acid-Functionalized Layered Double Hydroxide

Sorption methodologies play a pivotal role in heavy metal removal to meet the global requirements for uninterrupted access to drinkable water. Standard sorption technologies lack efficiency due to weak adsorbent-metal interaction. To this end, a layered cationic framework material loaded with phosphonate was first fabricated by a facile intercalation method to capture hazardous metals from an aqueous solution. To inquire the removal mechanisms, batch experiments, detection technologies, and simulation calculations were employed to study the interactions at the interface of clay/water. Specifically, the functionalized layered double hydroxide possessed excellent chelation adsorption properties with Zn²⁺ (281.36 mg/g) and Fe³⁺ (206.03 mg/g), in which model fitting results revealed that the adsorption process was chemisorption and monolayer interaction. Further, the interfacial interaction between the phosphonate and clay surface was evaluated by molecular dynamics simulation, and a new concept named the interaction region indicator was used to characterize weak interaction and coordinate bonds. The deep insight into the chelation mechanism was visually presented via the orbital interaction diagram. In addition, the regeneration of the spent adsorbent, adsorption column test, and acute toxicity analysis demonstrated that the synthesized material has immense potential in terms of practical usage for the treatment of toxic pollutants. These results provide a novel path for researchers to properly understand the adsorption behavior.

An In Situ Incorporation of Acrylic Acid and ZnO Nanoparticles into Polyamide Thin Film Composite Membranes for Their Effect on Membrane pH Responsive Behavior

This paper focuses on an in situ interfacial polymerization modification of polyamide thin film composite membranes with acrylic acid (AA) and zinc oxide (ZnO) nanoparticles. Consequent to this modification, the modified polyamide thin film composite (PA–TFC) membranes exhibited enhanced water permeability and Pb (II) heavy metal rejection. For example, the 0.50:1.50% ZnO/AA modified membranes showed water permeability of 29.85 ± 0.06 L·m⁻²·h⁻¹·kPa⁻¹ (pH 3), 4.16 ± 0.39 L·m⁻²·h⁻¹·kPa⁻¹ (pH 7), and 2.80 ± 0.21 L·m⁻²·h⁻¹·kPa^−1 1 (pH 11). This demonstrated enhanced pH responsive properties, and improved water permeability properties against unmodified membranes (2.29 ± 0.59 L·m⁻²·h⁻¹·kPa⁻¹, 1.79 ± 0.27 L·m⁻²·h⁻¹·kPa⁻¹, and 0.90 ± 0.21 L·m⁻²·h⁻¹·kPa⁻¹, respectively). Furthermore, the rejection of Pb (II) ions by the modified PA–TFC membranes was found to be 16.11 ± 0.12% (pH 3), 30.58 ± 0.33% (pH 7), and 96.67 ± 0.09% (pH 11). Additionally, the membranes modified with AA and ZnO/AA demonstrated a significant pH responsiveness compared to membranes modified with only ZnO nanoparticles and unmodified membranes. As such, this demonstrated the swelling behavior due to the inherent “gate effect” of the modified membranes. This was illustrated by the rejection and water permeation behavior, hydrophilic properties, and ion exchange capacity of the modified membranes. The pH responsiveness for the modified membranes was due to the –COOH and –OH functional groups introduced by the AA hydrogel and ZnO nanoparticles.

Separation of pollutants from aqueous solution using nanoclay and its nanocomposites: A review

Wastewater is always composed of different pollutants, most of which are toxic to the living being. It is very tough to separate all those diverse groups of contaminants using a single process or single material. Rather a sustainable and environment friendly processes should be adapted to restrict the secondary pollution generation. Nanoclay and its nanocomposites are one of the most used adsorbents that have been modified and used for the separation of almost all types of pollutants, including dyes, heavy metals, fluoride, nitrate, ammonia, emerging pollutants and bacteria. They are relatively inexpensive, easy to exploit and relatively maintenance-free. Thus, recent research bloomed for developing suitable adsorbents, including clay nanocomposites. The advantages and drawbacks of all the clay nanocomposites-based processes have been discussed critically in this article. Nano-clays or other nanoparticles incorporated synthetic and natural polymers-based clay nanocomposites were synthesized, and it was found that they can remove dyes in the range between 48 mg/g and 1994 mg/g. Similarly, they separate a diverse group of heavy metal ions, including As, Cu, Co, Pd, Zn, Cr, Ni, Cd, and Hg, in the range of 0.073-1667 mg/g. The clay nanocomposites also showed fluoride removal efficacy in the range of 0.134-23 mg/g. They are also useful for the separation of emerging pollutants like pesticides, pharmaceuticals, personal care products, trace elements, and particulate matters in the range of 0.1-651 mg/g the clay nanocomposites showed considerable nitrate, ammonia and bacteria removal efficacy too. Though it seems promising, more investigations with real wastewater and pilot-scale studies are recommended to explore large-scale wastewater treatment capabilities.

Synthesis and Characterization of Antibacterial Carbopol/ZnO Hybrid Nanoparticles Gel

This study recommends Carbopol/zinc oxide (ZnO) hybrid nanoparticles gel as an efficient antibacterial agent against different bacterial species. To this end, ZnO nanoparticles were synthesized using chemical precipitation derived from a zinc acetate solution with ammonium hydroxide as its precipitating agent under the effect of ultrasonic radiation. The synthesized ZnO nanoparticles were stabilized simultaneously in a freshly prepared Carbopol gel at a pH of 7. The chemical composition, phase identification, particle size and shape, surface charge, pore size distribution, and the BET surface area of the ZnO nanoparticles, as well as the Carbopol/ZnO hybrid Nanoparticles gel, were by XRD, SEM, TEM, AFM, DLS, Zeta potential and BET instruments. The results revealed that the synthesized ZnO nanoparticles were well-dispersed in the Carbopol gel network, and have a wurtzite-crystalline phase of spherical shape. Moreover, the Carbopol/ZnO hybrid nanoparticles gel exhibited a particle size distribution between ~9 and ~93 nm, and a surface area of 54.26 m2/g. The synthesized Carbopol/ZnO hybrid nanoparticles gel underwent an antibacterial sensitivity test against gram-negative K. pneumonia (ATCC 13883), Bacillus subtilis (ATCC 6633), and gram-positive Staphylococcus aureus (ATCC 6538) bacterial strains, and were compared with ampicillin as a reference antibiotic agent. The obtained results demonstrated that the synthesized Carbopol/ZnO hybrid nanoparticles gel exhibited a compatible bioactivity against the different strains of bacteria.

Adsorption of Cr(VI), Ni(II), Fe(II) and Cd(II) ions by KIAgNPs decorated MWCNTs in a batch and fixed bed process

The efficient removal of toxic metals ions from chemical industry wastewater is considered problematic due to the existence of pollutants as mixtures in the aqueous matrix, thus development of advanced and effective treatment method has been identified as a panacea to the lingering problems of heavy metal pollution. In this study, KIAgNPs decorated MWCNTs nano adsorbent was developed using combination of green chemistry protocol and chemical vapor deposition techniques and subsequently characterized using UV-Vis, HRTEM, HRSEM, XRD, FTIR and XPS. The adsorptive efficiency of MWCNTs-KIAgNPs for the removal of Cr(VI), Ni(II), Fe(II), Cd(II) and physico-chemical parameters like pH, TDS, COD, BOD, nitrates, sulphates, chlorides and phosphates from chemical industrial wastewater was examined in both batch and fixed bed systems. The result exhibited successful deposition of KIAgNPs on the surface of MWCNTs as confirmed by the microstructures, morphology, crystalline nature, functional groups and elemental characteristics of the MWCNTs-KIAgNPs. Optimum batch adsorption parameters include; pH (3 for Cr(VI) and 6 for Ni(II), Fe(II) and Cd(II) ions), contact time (60 min), adsorbent dosage (40 mg) and temperature (318 K). The binding capacities were obtained as follows; Cr⁶⁺ (229.540 mg/g), Ni²⁺ (174.784 mg/g), Fe²⁺ (149.552) and Cd²⁺ (121.026 mg/g), respectively. Langmuir isotherm and pseudo-second order kinetic model best described the experimental data in batch adsorption, while the thermodynamic parameters validated the chemisorption and endothermic nature of the adsorption process. In continuous adsorption, the metal ions were effectively removed at low metal influent concentration, low flow rate and high bed depth, whereby the experimental data were designated by Thomas model. The high physico-chemical parameters in the wastewater were successfully treated in both batch and fixed bed systems to fall within WHO permissible concentrations. The adsorption/desorption study illustrated over 80% metal removal by MWCNTs-KIAgNPs even after 8th adsorption cycle. This study demonstrated excellent performance of MWCNTs-KIAgNPs for chemical industry wastewater treatment.