Performance study on sequestration of copper ions from contaminated water using newly synthesized high effective chitosan coated magnetic nanoparticles

Recent breakthroughs on the development of electrodeionization systems for toxic pollutants removal from water environment

Since ecosystems are becoming inherently polluted, long-term contaminant removal methods are required. Electrodeionization, in particular, has recently been demonstrated as an effective approach for eliminating ionic compounds from contaminated water sources. Being a more environmentally friendly technology is most likely the main reason for its eminence. It uses electricity to replace toxic contaminants that are conventionally used to regenerate and hence reducing the toxins associated with resin regeneration. In wastewater treatment, continuous electrodeionization system overcomes several limitations of ion exchange resins, notably ion dumping. This prospective assessment delves into the mechanism, principle, and theory of electrodeionization system. It also focused on the design and applications, particularly in the removal of toxic compounds, as well as current advances in the electrodeionization system. Recent breakthroughs in electrodeionization were comprehensively discussed. Further developments in electrodeionization systems are also projected, with improved efficiency at the time of functioning at lower costs because of reduced energy use, proving them desirable for commercial usage with a broad array of applications across the globe.

Evaluation of the synergistic effect of chitosan metal ions (Cu2+/Co2+) in combination with antibiotics to counteract the effects on antibiotic resistant bacteria

The effectiveness of antibiotics that save millions of lives is in danger due to the increasing rise of resistant bacteria around the world. We proposed chitosan-copper ions (CSNP-Cu²⁺) and chitosan-cobalt ion nanoparticles (CSNP-Co²⁺) as biodegradable nanoparticles loaded with metal ions synthesized via an ionic gelation method for treatment of antibiotic resistant bacteria. The nanoparticles were characterized using TEM, FT-IR, zeta potential and ICP-OES. The MIC was evaluated for the NPs in addition to evaluating the synergetic effect of the nanoparticles in combination with cefepime or penicillin for five different antibiotic resistant bacterial strains. In order to investigate the mode of action, MRSA, DSMZ 28766 and Escherichia coli E0157:H7 were selected for further evaluation of antibiotic resistant genes expression upon treatment with NPs. Finally, the cytotoxic activities were investigated using MCF7, HEPG2 and A549 and WI-38 cell lines. The results showed quasi spherical shape and mean particle size of 19.9 ± 5 nm, 21 ± 5 nm and 22.27 ± 5 for CSNP, CSNP-Cu²⁺ and CSNP-Co²⁺ respectively. FT-IR showed slight shifting of the hydroxyl and amine group's peaks of chitosan indicating the adsorption of metal ions. Both nanoparticles had antibacterial activity with MIC ranging between 125 and 62 μg ml^-1 for the used standard bacterial strains. Moreover, the combination of each of the synthesized NP with either cefepime or penicillin not only showed a synergetic effect as antibacterial activity of each NP or antibiotics alone, but also decreased the fold of antibiotic resistance genes expression. The NPs showed potent cytotoxic activities for MCF-7, HepG2 and A549 cancer cell lines with lower cytotoxic values for the WI-38 normal cell line. The NPs' antibacterial activity may be due to penetration and rupture of the cell membrane and the outer membrane of Gram negative and Gram positive bacteria causing bacterial cell death, in addition to, penetration into the bacterial genes and blocking gene expression that is vital to bacterial growth. The fabricated nanoparticles can be an effective, affordable and biodegradable solution to challenge antibiotic resistant bacteria.

Water-based Fe3O4 magnetic fluid-coated Aspergillus niger spores for treating liquid contaminated with Cr(VI)

The use of magnetic biosorbents for the remediation of heavy metals has attracted increasing attention due to their ease of separation and reusability. We developed a method for preparing superparamagnetic biosorbent materials using water-based magnetic fluids. Water-based magnetic fluid-spores (WMFSs) were obtained by combining water-based magnetic fluid (WMF) with Aspergillus niger spores at ratios of 0.6:1 (WMFS1), 0.8:1 (WMFS2), 1:1 (WMFS3), 1.2:1 (WMFS4), and 1.4:1 (WMFS5). A magnetic composite material was prepared from magnetic nanoparticles and spores in a ratio of 1:1 as a control. The adsorption efficiency and separation effect of WMFS3 were significantly better than those of the magnetic composite material. The morphology and structure of WMFS3 were characterized by performing transmission electron microscopy. The results showed that Fe₃O₄ magnetic particles were uniformly coated on the spore surface. The superparamagnetism of WMFS3 was tested using a vibrating sample magnetometer. At pH 2.0, the maximum adsorption capacity of WMFS3 for Cr(VI) was 105 mg/g; in the pH range of 2.0-3.0, the adsorption equilibrium time of WMFS3 was 60 min. Thus, the adsorption process conformed to the pseudo-second-order kinetic model and Freundlich isotherm. Thermodynamic studies showed that the process was spontaneous and endothermic. The adsorption mechanisms of WMF3 for Cr(VI) included electrostatic, reduction, and complexation adsorption. This biosorbent material showed excellent adsorption performance for Cr(VI) and is promising for wastewater resource applications.

Insights on synthesis and applications of graphene-based materials in wastewater treatment: A review

Graphene has excellent unique thermal, chemical, optical, and mechanical properties such as high thermal conductivity, high chemical stability, optical transmittance, high current density, higher surface area, etc. Due to their outstanding properties, the attention towards graphene-based materials and their derivatives in wastewater treatment has been increased in recent times. Different graphene-based materials such as graphene oxides, graphene quantum dots, graphene nanoplatelets, graphene nanoribbons and other graphene-based nanocomposites are synthesized through chemical vapor deposition, mechanical and electrochemical exfoliation of graphite. In this review, the specifics about the graphenes and their derivatives, the synthesis strategy of graphene-based materials are described. This review critically explained the applications of graphene-based materials in wastewater treatment. Graphene-based materials were utilized as adsorbents, electrodes, and photocatalysts for the efficient removal of toxic pollutants such as heavy metals, dyes, pharmaceutics, antibiotics, phenols, polycyclic aromatic hydrocarbons have been highlighted and discussed. Herein, the potential scope of graphene-based material in the field of wastewater treatment is critically reviewed. In addition, a brief perspective on future research directions and difficulties in the synthesis of graphene-based material are summarized.

Surface treated Phoenix sylvestris for bioadsorption of oil from aqueous solution: Isotherms and kinetic studies

Biosorption is a versatile technique of removing the oil spill - one of the major toxicants that causes water pollution, which threatens the ecological balance of the aquatic ecosystem. The proposed research aims in developing a viable adsorbent from discarded agricultural waste, Phoenix sylvestris, which was surface altered, assessed and utilised as a biosorbent for the effective removal of diesel from aqueous solution in batch adsorption trials. Waste palm leaves, Phoenix sylvestris (RPS)was physically (PMPS) and chemically modified (CMPS) to adsorb diesel in the emulsion. The synthesised materials were characterised by FTIR, SEM, and EDS, confirming a well-defined microporous structure consisting of ionisable groups. The studies indicated optimised conditions of 10 g, 4.5 g and 2 g of RPS, PMPS and CMPS respectively at 303K for an optimised adsorption time of 60 min. Freundlich isotherm agreed well with experimental data, and the kinetic mechanism claimed better results with RPS, PMPS and CMPS for Pseudo first-order model. The adsorbents could be reused five times without much loss of efficiency. From the performed studies, it can be inferred that good adsorption capacities at optimised conditions followed the order of CMPS > PMPS > RPS. Thermodynamic analysis proved the feasibility of such biosorption with exothermic nature predicting spontaneous attraction of oil components to the surface of PMPS and CMPS. Moreover, the density of the CMPS layer rendered proven results for such biosorption displaying a hyperbolic dependency assuring its efficacy. Hence, it can be concluded that the prepared adsorbent from Phoenix sylvestris, an agricultural waste, possess good adsorptive properties.

Effect of magnetization on the adsorptive removal of an emerging contaminant ciprofloxacin by magnetic acid activated carbon

Magnetic acid activated carbons (MAAC) were prepared from the shells of Sterculia villosa Roxb by activating the biomass and magnetizing it using the co-precipitation technique. Characterization of MAAC prior and post adsorption was performed using various microscopic and spectroscopic analytical techniques, and they verified the formation of magnetic aggregates over porous activated carbon surface. Vibrating Sample Magnetometer (VSM) analysis confirmed the superparamagnetic behaviour of the adsorbent with saturation magnetization (Ms) value of 18.2 emu/g, causing an easy and rapid recovery from the adsorption setup in the presence of an external magnetic field. Langmuir isotherm and pseudo-second-order kinetic model best fit the experimental data with theoretical Langmuir maximum adsorption capacity as 81.97 mg/g and verifying chemisorption type of adsorption process, respectively. Thermodynamic analysis verified the interaction among adsorbate and adsorbent as endothermic, spontaneous, and thermodynamically favourable. Co-existing metal cations showed a significant reduction in ciprofloxacin removal efficiency; co-existing anions, though, showed a negligible influence on the adsorption efficiency of MAAC. Recyclability studies verified that the adsorption efficiency fell from 98% in the first cycle to 43% in the fifth cycle. The Ms value fell to 7.6 emu/g (after five adsorption cycles), affecting the adsorbent's recovery. The Phyto-toxicological assessment was performed to evaluate the environmental risk to human and aquatic life using Vigna mungo seeds. MAAC proved to be an effective and magnetically separable adsorbent for removing antibiotics.

Chitosan as a Tool for Sustainable Development: A Mini Review

New developments require innovative ecofriendly materials defined by their biocompatibility, biodegradability, and versatility. For that reason, the scientific society is focused on biopolymers such as chitosan, which is the second most abundant in the world after cellulose. These new materials should show good properties in terms of sustainability, circularity, and energy consumption during industrial applications. The idea is to replace traditional raw materials with new ecofriendly materials which contribute to keeping a high production rate but also reducing its environmental impact and the costs. The chitosan shows interesting and unique properties, thus it can be used for different purposes which contributes to the design and development of sustainable novel materials. This helps in promoting sustainability through the use of chitosan and diverse materials based on it. For example, it is a good sustainable alternative for food packaging or it can be used for sustainable agriculture. The chitosan can also reduce the pollution of other industrial processes such as paper production. This mini review collects some of the most important advances for the sustainable use of chitosan for promoting circular economy. Hence, the present review focuses on different aspects of chitosan from its synthesis to multiple applications.

Adsorption performance of activated carbon synthesis by ZnCl2, KOH, H3PO4 with different activation temperatures from mixed fruit seeds

In this study, new activated carbons (ACs) were synthesized from a mixture of lemon and orange seeds (LOS) for toxic metal removal from aqueous solutions. Adsorbents have been produced by chemical activation with different activation agents (with H₃PO₄, ZnCl₂ and KOH) and activation temperature (600°C, 700°C, 800°C). The elemental analysis, FT-IR, XRD and SEM analyses were performed to determine the characterization of the ACs. A series of batch adsorption experiments were done to research the influence of various parameters such as pH, adsorbent dosage, contact time, temperature, the complexing agents on the toxic metal ions (Cu(II), Cr(III) and Ni(II)) removal capacity of ACs. Adsorption equilibration time was 60 min, the adsorption capacity was 118.02 mg/g for Ni(II) ions, 146.03 mg/g for Cr(III) ions and 150.45 mg/g for Cu(II) ions. The adsorption of toxic metal ions was observed as a maximum at pH = 5 on AC-ZnCl₂ (600°C) produced under N₂ atmosphere. The adsorption process was fitted with a Langmuir isotherm model and a pseudo-second-order kinetic equation, showing the metal ions adsorption on AC was monolayer coverage. Thermodynamic studies show that the adsorption is endothermic and spontaneous in nature. AC produced from the LOS mixture has not been encountered in the literature. A simple, easy-to-apply method has been developed for a new adsorbent prepared from a mixture of LOS with environmentally friendly, easy to produce, reusable, cost-effective, non-toxic and with good adsorption-desorption capacity. Therefore, this study will contribute to the world economy in terms of environmental and wastewater cleaning.

Synthesis and characterization of rhamnolipid based chitosan magnetic nanosorbents for the removal of acetaminophen from aqueous solution

Biocatalytically synthesized mono-rhamnolipids are eco-friendly surfactants that exhibit strong industrial applications owing to their low toxicity and biodegradability as well as their efficient antimicrobial and surface tension reduction potential. In this present study, novel adsorbent chitosan encapsulated magnetic nanoparticles coated with rhamnolipids (Rh-cMNP) were prepared and used for the adsorption of the micropollutant acetaminophen. The SEM, FTIR, and VSM results showed that Rh-cMNP had abundant functional groups with a mesoporous feature and easy separation of the magnetic nanosorbent from the reaction mixture. The obtained nanosorbent was effectively used to remove acetaminophen, one of the most common persistent pharmaceutical pollutants in the environment. Optimization studies revealed the maximum removal of 96.7% acetaminophen with the ability of adsorption to be 96.3 mg/g at 60 min of contact time and process parameters of pH 5.0 and 303 K temperature. Langmuir isotherm was most favourable for the optimized data; kinetic studies obeyed pseudo-second-order whose feasibility and thermodynamic studies obtained spontaneity. Regeneration of used Rh-cMNP is performed with 0.1 N HCl/NaOH and observed to be consistent for eight adsorption-desorption cycles.

Removal of metal ions using a new magnetic chitosan nano-bio-adsorbent; A powerful approach in water treatment

In this study, a magnetic chitosan/Al₂O₃/Fe₃O₄ (M-Cs) nanocomposite was developed by ethylenediaminetetraacetic acid (EDTA) functionalization to enhance its adsorption behavior for the removal of Cd(II), Cu(II) and Zn(II) metal ions from aqueous solution. The results revealed that the EDTA functionalization of M-Cs increased its adsorption capacity ~9.1, ~5.6 and ~14.3 times toward Cu, Cd and Zn ions. The maximum adsorption capacity followed the order of Cd(II) > Cu(II) > Zn(II) and the maximum adsorption efficiency was achieved at pH of 5.3 with the removal percentage of 99.98, 93.69 and 83.81 %, respectively, for the removal of Cu, Cd and Zn ions. The metal ions adsorption kinetic obeyed pseudo-second-order equation and the Langmuir isothermal was found the most fitted model for their adsorption isothermal experimental data. In addition, the thermodynamic study illustrated that the adsorption process was exothermic and spontaneous in nature.

A review on recent trends in the removal of emerging contaminants from aquatic environment using low-cost adsorbents

Emerging contaminants (ECs), a class of contaminants with low concentrations but significant harm, have received a lot of attention in recent times. ECs comprises of various chemicals that enter the environment every day. In today's modern lifestyle, we use many chemical-based products. These persist in wastewater and ultimately enter the water bodies, causing serious problems to the human and aquatic ecosystem. This is because the conventional wastewater treatment methods are inefficient in identifying and removing such contaminants. Aiming for a long-term, effective solution to this issue, Adsorption was proposed. Although several adsorbents are already present in the market, which have proved beneficial in removing such ECs, not all are affordable. This article reviews replacing costly adsorbents with agriculture-based biomass that are abundant, inexpensive, and biodegradable and possess excellent adsorption capacity. The objectives of this article is to look at adsorption as a viable treatment option for emerging pollutants, as well as sophisticated and cost-effective emerging contaminants treatment options.

Fabrication of Electrochemical Sensor for Epinine Determination Amplified with MgO/CNTs Nanocomposite and Ionic Liquid

Background:

Catecholamines are a large group of pharmacological and biological compounds that are widely used in biological systems. These compounds are prepared both naturally and synthetically with many key roles in the human body and its activities. Therefore, many researchers focused on the identification and determination of catecholamines in biological samples.

Methods:

MgO/SWCNTs were synthesized through the chemical precipitation method. In addition, cyclic voltammetry, differential pulse voltammetry, and chronoamperometric methods were used for the electro-oxidation reaction study of epinine at the surface of the modified electrode.

Results:

Carbon paste electrode (CPE) modified with MgO/SWCNTs nanocomposite and 1-butyl- 3-methylimidazolium methanesulfonate (BMMS) was used as an electrochemical sensor for the determination of epinine. The results showed a linear dynamic range of 5.0 nM-250 μM with a detection limit of 0.1 nM for epinine determination using MgO/SWCNTs/BMMS/CPE as a sensor.

Conclusion:

In the present study, a highly sensitive electrochemical sensor was designed and fabricated as an analytical tool for the determination of epinine. MgO/SWCNTs/BMMS/CPE was successfully used for the determination of epinine in water and dextrose saline with an acceptable recovery range of 98.7%-102.72%.

Genotypic diversity of 17 cacti species and application to biosynthesis of gold nanoparticles

The genotypic diversity of 17 cacti species were examined and grouped in four clusters using seven inter simple sequence repeat (ISSR) markers. Group representatives (five species) were chosen for AuNPs synthesis in the cacti syrups. To synthesize the Gold nanoparticles (AuNPs), reducing and capping potential of five species of cacti rich in the polyphenolics were explored. Based on the synthesized AuNPs traits (concentration, pH, temperature, and synthesis time), Opuntia pycnacantha with the highest absorption peak at 540 nm was chosen for further characterizations. Varieties of diffraction peaks confirmed the successful synthesis of AuNPs. AuNPs functionalization with the phenolic compounds was confirmed by Fourier transform infrared (FTIR) spectroscopy. At the optimum conditions (pH = 5.0 and T = 60 °C), both dynamic light scattering (DLS) and transmission electron microscopy (TEM) revealed more than 87% of AuNPs to be 2.5 nm in size with Zeta potential to be equal to -19.9 mV.

A detailed insight on fabricated porous chitosan in eliminating synthetic anionic dyes from single and multi-adsorptive systems with related studies

Chitosan was fabricated via gelation method using CaBr₂.xH₂O/methanol solution and was studied as a potential adsorbent (MCh) in adsorbing anionic synthetic dyes like Bromophenol blue (BB), Direct blue 6 (DB) and Congo red (CR) from single (one dye species at a time) and multi (having two dyes; binary and all three dyes; tertiary) adsorptive systems. Physico-chemical modifications of MCh surface prior and post modification and dye adsorption were evaluated using scanning electron microscopy, Energy-dispersive X-ray spectroscopy, powder X-ray diffraction analysis, surface area analysis and Fourier-transformed infrared spectroscopy. Influential parameters influencing the adsorption process viz. initial pH of dye solution, MCh dosage, adsorption temperature and initial concentration of dye species were optimised. Adsorptive studies involving single adsorptive setups verified formation of sorbate's (dye species) monolayer over the sorbent's (MCh) surface via chemisorption; as established by Langmuir isotherm and pseudo-second order kinetics model analysis. Theoretical maximum adsorption capacities of MCh for BB, DB and CR was found to be 81.301 mg/g, 163.934 mg/g and 75.758 mg/g, respectively. Meanwhile, for all multi-adsorptive systems, competitive Langmuir isotherm model verified antagonistic behaviour of an individual dye over other dye adsorption over MCh surface in their respective adsorptive systems. Thermodynamics of the sorbate-sorbent interaction was exothermic, spontaneous, with elevated degree of disorderedness; concluding the interaction as thermodynamically favourable. Co-existing metal cations and anionic salts had minimal effect on MCh's adsorption efficiency. Phytotoxicity assay via germination of Vigna mungo seeds verified the efficacy of the adsorbent in eliminating the dye species from single and multi-adsorptive systems.

Heterogeneous UV-Switchable Au nanoparticles decorated tungstophosphoric acid/TiO2 for efficient photocatalytic degradation process

In the present study, gold nanoparticles were locally well-decorated on the surface of TiO₂ using the tungstophosphoric acid (HPW), as UV-switchable reducing intermediate linkers. The prepared Au NPs/HPW/TiO₂ nanostructure was characterized using FTIR, XRD, EDS, SEM and TEM, which confirmed the successful attachment of quasi-spherical Au NPs in the range of 20-30 nm on the surface of HPW modified TiO₂. Also, the FTIR results show that the Au NPs were binded to TiO₂ through the terminal the oxygen atoms HPW. The photocatalytic performance of prepared nanostructures was assessed in degradation of nitrobenzene. The nitrobenzene photodegradation kinetic study revealed that it well followed the Langmuir-Hinshelwood kinetic model with the apparent rate constant of 0.001 min^-1 using anatase TiO₂, 0.0004 min^-1 using HPW, 0.0014 using HPW/TiO₂, while it was obtained 0.0065 min^-1 using Au NPs@HPW/TiO₂ nanostructure. It shows that the photocatalytic rate of the prepared nanocomposites increased by 6.5- and 4.6-fold compared to photoactivity of anatase TiO₂ and HPW/TiO₂ respectively. Also, the photocatalytic mechanism of process was proposed. Moreover, the reusability study confirmed that its photocatalytic activity still remained high after three cycles.

Recent technologies for nutrient removal and recovery from wastewaters: A review

Water scarcity and its pollution has become a concern in recent times. The disposal of nutrient-rich (nitrogen and phosphorous) wastewater is also one of the main cause of water pollution through eutrophication, reduced dissolved oxygen that poses threat to aquatic ecosystems. As a result, nutrient removal has become a mandate apart from the removal of organics. However, the removal of nutrients from sewage is a challenging task. Conversely, conventional biological treatment processes provide little relief in nutrient removal. The treated effluents from conventional biological processes do not achieve the stringent nutrient removal disposal standard limits and become primary cause of pollution in the receiving water bodies. This has stressed upon the need for eco-friendly, low-energy and cost-efficient nutrient removal treatment technologies. Various biological treatment combinations or variants are in use for the efficient removal of nutrients. The biological processes in itself or in combination with chemical processes are preferred over technologies based solely on physico-chemical processes for its treatment performance at lower cost. This review summarizes the existing treatment processes and their possible up-gradation with the aim to accomplish the marked effluent standards for the nutrients. The concept of conventional systems and advanced systems for nutrients (nitrogen and phosphorous) removal which are already developed or under development are deeply discussed. Further, the challenges of each treatment systems are abridged. Finally, the possible suggestions for the modification/retrofitting of existing treatment systems for achieving stringent disposal standards are pointed out.

Effects of silver nanoparticles added into polyurea coating on sulfate-reducing bacteria activity and electrochemical properties; an environmental nano-biotechnology investigation

In the present work, Ag nanoparticles were added to polyurea coating in order to improve its antibacterial and electrochemical properties in sulfide-reducing bacteria-containing media. To this end, Ag nano-powder was mixed with two component polyuria, and then the antibacterial behavior of the nanocomposite coating was studied in sulfate-reducing bacteria (SRB)-containing medium. The results revealed the inhibitory effects of nanocomposite coating on the formation of SRB biofilms on the samples. Moreover, the SRB population decreased in contact with the Ag nanoparticles-mixed coating over 7 days. Investigation of the growth and activity of the bacteria represented the effective antibacterial properties of Ag nanoparticles in the polyurea matrix. Furthermore, EIS (electrochemical impedance spectroscopy) measurements indicated that the corrosion properties of the nanocomposite coating improved considerably over 7 days. The coating resistance increased 2 times by adding Ag nanoparticles after 1 day and 3.3 times after 7 days. In accordance with the same results, the charge transfer resistance increased 1.5 times and 1.1 times by adding Ag nanoparticles after 1 day and 7 days, respectively. The improvement in the protective properties of the nanocomposite coating are reflected in the increase in both film and charge transfer resistance.

Application of adsorption process for effective removal of emerging contaminants from water and wastewater

Emerging pollutants in the marine ecosystem, as well as their possible impact on live species, have become a rising cause of worry. A traditional wastewater treatment plants alone are not successful in eliminating such massive contaminant groups and therefore additional water treatment is required which is to be cost effective. Since standard primary and secondary treatment plants are unsuccessful at eliminating or degrading these harmful chemicals, a cost-effective tertiary treatment approach is proposed. Adsorption is a successful approach for Contaminants removal globally, because it is low installation expense, high performance and has easy operational design. Emerging pollutants have been removed from wastewaters using various adsorbents like activated carbons, improved bio chars, Nano adsorbents, hybrid adsorbents, and others. The purpose of this paper is to review the source of contaminants and the concept of adsorption when separating emerging contaminants. The present study aims to examine the adsorption mechanism as an effective approach for treating emerging contaminants. Then, the analysis of natural and man-made adsorbents for the separation of contaminants is examined along with its comparison. Also, future view on emerging contaminants and adsorbents in modern generation has been discussed.

Performance study on adsorptive removal of acetaminophen from wastewater using silica microspheres: Kinetic and isotherm studies

Owing to the global industrialization, a new generation of pharmaceutical pollutants with high toxicity and persistency have been detected. In the present study, silica microspheres, a promising adsorbent has been employed to investigate the extent of removal of prevalent therapeutic acetaminophen, an emerging micropollutant, from wastewater in isolated batch experiments. The BET surface area of the adsorbent was 105.46 m²/g with a pore size of 15 nm. Characterization of adsorbent by scanning electron microscopy analysis revealed the microparticulate nature with a 15 ± 5 μm particle size. Optimization of reaction parameters for enhanced assimilative removal of pollutants was performed and the highest adsorption of 96.7% of acetaminophen with an adsorption capacity of 89.0 mg/g was observed upon contact time of only 30 min. Mild process conditions of pH 5.0, 20 ppm of acetaminophen, temperature of 303 K, and 100 ppm sorbent concentration further aided in the removal process. Obtained data were best corresponded with the Freundlich isotherm (n = 2.685), indicating highly favorable adsorption. Acetaminophen adsorption kinetics obeyed the pseudo second order and feasible energetic changes were yielded through the thermodynamic analysis. Silica microspheres recovery carried out through a single-step desorption process had a 99.14% retrieval ability.

A review on effective removal of emerging contaminants from aquatic systems: Current trends and scope for further research

Wastewater is water that has already been contaminated by domestic, industrial and commercial activity that needs to be treated before it could be discharged into some other water bodies to avoid even more groundwater contamination supplies. It consists of various contaminants like heavy metals, organic pollutants, inorganic pollutants and Emerging contaminants. Research has been doing on all types of contaminates more than a decade, but this emerging contaminants is the contaminants which arises mostly from pharmaceuticals, personal care products, hormones and fertilizer industries. The majority of emerging contaminants did not have standardized guidelines, but may have adverse effects on human and marine organisms, even at smaller concentrations. Typically, extremely low doses of emerging contaminants are found in the marine environment and cause a potential risk to the aquatic animals living there. When contaminants emerge in the marine world, they are potentially toxic and pose many risks to the health of both man and livestock. The aim of this article is to review the Emerging contaminate sources, detection methods and treatment methods. The purpose of this study is to consider the adsorption as a beneficial treatment of emerging contaminants also advanced and cost effective emerging contaminates treatment methods.

A review on cleaner strategies for extraction of chitosan and its application in toxic pollutant removal

Existence of human beings in this world require a cleaner environment, in which, water is the main requirement for living. Owing to the considerable development in civilisation and considerable population explosion, an increase in the contamination of natural water resources by means of non-biodegradable contaminants like heavy metals is observed thereby increasing the need for treatment of water before usage. Despite the existence of specific limits for disposal of heavy metals in water resources, studies still show high contamination of heavy metals in all these water resources. This review provides a brief note on sources and toxicity of different heavy metals in various oxidation states, their effects as well as highlights the numerous available and advanced techniques for heavy metals removal. Of all techniques adsorption is found to be beneficial as it doesn't inculcate any secondary pollutants to the environment. Additionally, this article has investigated the advantages of polymer nanocomposites in adsorption and mainly focused on biopolymer chitosan owing to its abundance in natural environment. The cleaner techniques for the extraction of chitosan and its functionalisation using different types of nanofillers are comprehensively discussed in this review. This article suggests a better alternative for conventional adsorbents as well as aids in remediation of wastes.

Biodegradable gelatin composite hydrogels filled with cellulose for chromium (VI) adsorption from contaminated water

Biopolymers are promising materials for water treatment applications due to their abundance, low cost, expandability, and chemical structure. In this work, gelatin hydrogels filled with cellulose in the form of pristine eucalyptus residues (PER) or treated eucalyptus residues (TER) were prepared for adsorption and chromium removal in contaminated water. PER is a lignocellulosic compound, with cellulose, hemicellulose, and lignin, while TER has cellulose as a major component. FT-Raman Spectroscopy and FTIR analysis confirmed the crosslink reaction with glutaraldehyde and indicated that fillers altered the gelatin molecular vibrations and formed new hydrogen bonds, impacting the hydrogels' crystalline structure. The hydrogen bond energy was altered by the cellulosic fillers' addition and resulted in higher thermal stability (~10 °C). Hydrogels presented a Fickian diffusion, where gelatin hydrogel showed the highest swelling ability (466%), and composites showed lower values with the filler content increase. The chromium adsorption capacity presented values between 12 and 13 mg/g, i.e., featuring an excellent removal capacity which is related with hydrogel crosslinked structure and fibers surface hydroxyl groups, highlighting gelatin hydrogel TER 5% with better removal capacity. The developed hydrogels were produced from biomacromolecules with low-cost and potential application in contaminated water.

A review on biosynthesis of metal nanoparticles and its environmental applications

Nanotechnology has become one of the emerging multi-disciplinary fields receiving universal attention and playing a substantial role in agriculture, environment and pharmacology. In spite of various techniques employed for nanoparticle synthesis such as laser ablation, mechanical milling, spinning and chemical deposition, usage of hazardous chemicals and expensiveness of the process makes it unsuitable for the continuous production. Hence the necessity of sustainable, economic and environment friendly approach development have increased in recent years. Microbial synthesis of nanoparticles connecting microbiology and nanotechnology is one of the green techniques employed for sustainable production. Gold, silver and other metal nanoparticles like platinum, palladium, molybdenum nanoparticles biosynthesis by bacteria, fungi, yeast and algae have been reported in the present review. On account of microbial rich community, several microbes have been explored for the production of nanoparticles. Nanoparticles are also employed for environmental remediation processes such as pollutant removal and detection of contaminants. Lack of monodispersity and prolonged duration of synthesis are the limitations of bio-synthesis process which can be overcome by optimization of methods of microbial cultivation and its extraction techniques. The current review describes the different microbes involved in the synthesis of nanoparticles and its environmental applications.

Asparagine modified downconversion NaGdF4:Dy3+/Tb3+ nanophosphor for selective and sensitive detection of Cu(ii) ion

Pure NaGdF4, NaGdF4:Dy3+, and Dy3+/Tb3+ co-doped NaGdF4 nanoparticles with different concentrations of Tb3+ (ranging from 3 to 20 mol%) were prepared via hydrothermal method.

A critical review on the biochar production techniques, characterization, stability and applications for circular bioeconomy

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Recent research on remediation of toxic pollutants by biochar has been summarized.

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The production techniques of the biochar have been narrated.

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Biochar properties, stability and its environmental issues have been analysed.

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Applications of biochar in soil fertility and removing pollutants have been reported.

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The major stumbling block in biochar production is cost of production.

There is an upsurge enthusiasm for utilizing biochar produced from waste-biomass in different fields, to address the most important ecological issues. This review is focused on an overview of remediating harmful contaminants utilizing biochar. Production of biochar utilizing various systems has been discussed. Biochar has received the consideration of numerous analysts in building up their proficiency to remediate contaminants. Process parameters are fundamentally answerable for deciding the yield of biomass. Biochar derived from biomass is an exceptionally rich wellspring of carbon produced from biomass utilizing thermal combustion. Activating biochar is another particular region for the growing utilization of biochar for expelling specific contaminations. Closed-loop systems to produce biochar creates more opportunities. Decentralized biochar production techniques serve as an effective way of providing employment opportunities, managing wastes, increasing resource proficiency in circular bioeconomy. This paper also covers knowledge gaps and perspectives in the field of remediation of toxic pollutants using biochar.

Adsorption, degradation, and mineralization of emerging pollutants (pharmaceuticals and agrochemicals) by nanostructures: a comprehensive review

This review discusses a fresh pool of research findings reported on the multiple roles played by metal-based, magnetic, graphene-type, chitosan-derived, and sonicated nanoparticles in the treatment of pharmaceutical- and agrochemical-contaminated waters. Some main points from this review are as follows: (i) there is an extensive number of nanoparticles with diverse physicochemical and morphological properties which have been synthesized and then assessed in their respective roles in the degradation and mineralization of many pharmaceuticals and agrochemicals, (ii) the exceptional removal efficiencies of graphene-based nanomaterials for different pharmaceuticals and agrochemicals molecules support arguably well a high potential of these nanomaterials for futuristic applications in remediating water pollution issues, (iii) the need for specific surface modifications and functionalization of parent nanostructures and the design of economically feasible production methods of such tunable nanomaterials tend to hinder their widespread applicability at this stage, (iv) supplementary research is also required to comprehensively elucidate the life cycle ecotoxicity characteristics and behaviors of each type of engineered nanostructures seeded for remediation of pharmaceuticals and agrochemicals in real contaminated media, and last but not the least, (v) real wastewaters are extremely complex in composition due to the mix of inorganic and organic species in different concentrations, and the presence of such mixed species have different radical scavenging effects on the sonocatalytic degradation and mineralization of pharmaceuticals and agrochemicals. Moreover, the formulation of viable full-scale implementation strategies and reactor configurations which can use multifunctional nanostructures for the effective remediation of pharmaceuticals and agrochemicals remains a major area of further research.

Fabrication of novel amine-functionalized magnetic silica nanoparticles for toxic metals: kinetic and isotherm modeling

In this research, an amine-functionalized magnetic silica nanosorbent was prepared using the co-precipitation technique, and this nanosorbent can be effortlessly detached using an external magnetic field. FTIR and SEM analyses identified that the nanosorbent holds extraordinary adsorption characteristics for toxic metals' (copper, cadmium, zinc, and nickel) removal. The adsorption-affecting parameters were optimized, and the thermodynamic studies assessed that the adsorption process seemed to be spontaneous, feasible, and exothermic. The pseudo-first-order and Freundlich models perfectly fit the kinetic and equilibrium data, respectively. Langmuir monolayer capacity of the nanosorbent was analyzed using nonlinear evaluation methods such as 419.9 mg/g for copper, 321.9 mg/g for nickel, 217.3 mg/g for cadmium, and 137.6 mg/g for zinc. The used adsorbent was simply rejuvenated using the 0.2 N HCl solution subsequently with intense agitation. The result of the present research confirms that the produced nanosorbent can be effectively utilized for industrial wastewater management.

Microwave-assisted urea modified crop residue in Cu2+ scavenging

Raphia hookeri fruit epicarp (RHFE) was used in a novel adsorbent preparation via a combination of urea modification and microwave irradiation. The prepared adsorbent (URHFE) was characterized physicochemically, spectroscopically and microscopically characterized. URHFE efficiency in Cu²⁺ scavenging was tested with focus on operational parameters such as pH, dosage, concentration, contact time, ionic strength and temperature. Adsorption data were tested with isotherms and kinetics models. Optimum adsorption occurred at pH of 5.5. The presence of competing ion decreased Cu²⁺ removal and this varied with competing ion concentration. Cu²⁺ uptake decreased with increase in temperature. Percentage desorption was found generally low. The Langmuir monolayer adsorption capacity (q_max) was obtained to be 144.93 mg/g, this compared well in effectiveness with other adsorbent previously reported. Dubinin Radushkevich (D-R) isotherm model suggests that adsorption mechanism was chemical in nature. Pseudo second order kinetics best described the adsorption kinetics while multilinear adsorption was observed from the intraparticle diffusion model.

Metals and PFAS in stormwater and surface runoff in a semi-arid Canadian city subject to large variations in temperature among seasons

Because compounds accumulate through dry periods and enter aquatic systems in just a few seasonal events such as snowmelt and summer storms, surface waters in semi-arid, cold regions, such as the Canadian Prairies, are particularly vulnerable to loading of contaminant from runoff events from surfaces. This study assessed concentrations of metals and selected trace organics entering a river via surface runoff from an urban region and how these semi-arid regions with large seasonal variations in temperature might differ from more temperate regions. Selected potentially harmful elements (PHEs) including, Mn with Cr, Cu, Zn, Ba and U all exceeded guideline discharge values set by the Canadian Council of the Ministers of the Environment (CCME) by as much as 16-fold. Variation among discharges during spring, summer and winter was observed. For example, across the whole city, an estimated 6 kg of zinc was discharged in a spring storm, 36 kg in a summer storm and 17 tonnes in snowmelt. The mass of Zn discharged is similar to the annual loading estimated for Stockholm, Sweden, but in Saskatoon, Saskatchewan, Canada, the bulk of runoff was during snowmelt. The mean sum of poly- and per-fluoroalkyl substances (PFAS) in stormwater was 9.0 ng L^-1, which is consistent with concentrations observed in other Canadian cities (6.5-16 ng L^-1). These concentrations of PFAS are likely due to dispersed sources and orders of magnitude less than thresholds for toxicity to fish and aquatic invertebrates.

Processing and modification of hydrogel and its application in emerging contaminant adsorption and in catalyst immobilization: a review

Due to the wonderful property of hydrogels, they can provide a platform for a wide range of applications. Recently, there is a growing research interest in the development of potential hydrogel adsorbents in wastewater treatment due to their adsorption ability toward aqueous pollutants. It is important to prepare such a hydrogel that possesses appropriate robustness, adsorption capacity, and adsorption efficiency to meet the need of water treatment. In order to improve the property of hydrogels, much effort has been made by researchers to modify hydrogels, among which incorporating inorganic components into the polymeric networks is the most common method, which can reduce the product cost and simplify the preparation procedure. Not only can hydrogel be applied as adsorbent, but it also can be used as matrix for catalyst immobilization. In this review, the key advancement on the preparation and modification of hydrogels is discussed, with special emphasis on the introduction of inorganic materials into polymeric networks and consequential changes in the properties of mechanical strength, swelling, and adsorption. Besides, hydrogels used as adsorbents for removal of dyes and inorganic pollutants have been widely explored, but their use for adsorbing emerging contaminants from aqueous solution has not received much attention. Thus, this review is mainly focused on hydrogels' application in removing emerging contaminants by adsorption. Furthermore, hydrogels can be also applied in immobilizing catalysts, such as enzyme and photocatalyst, to remove pollutants completely and avoid secondary pollution, so their progress as catalyst matrix is overviewed.

Effects of fillers combined with biosorbents on nutrient and heavy metal removal from biogas slurry in constructed wetlands

The performance of fillers (biochar and zeolite) and their combinations with biosorbents (compound microbial agent and chlorella) in nutrients and heavy metals removal from biogas slurry in constructed wetlands (CWs) planted water spinach (Ipomoea aquatica) and plant uptake of heavy metals was investigated. The results demonstrated that the removal rate of nutrients in CWs was all above 60%. COD removal efficiencies were not significantly affected by fillers and biosorbents, all above 80%. The removal rates of TN and NH₄⁺-N were the highest when the two fillers and two biosorbents were added, and the combination of biochar and chlorella presented the optimal removal effect on TP. The efficiency of removing heavy metals from biogas slurry in CWs was As > Zn > Cu, and their removal rates were 35.38%-83.89%, 8.15%-23.69% and 0.32%-0.88%, respectively. The removal efficiency of As by the combination of biochar and composite microbial agent was high. The combination of the two fillers and two biosorbents had the best effect on reducing Cu and Zn enrichment in the aboveground part of water spinach in each treatment, while biochar alone had the best effect on reducing As enrichment in the aboveground and underground parts of water spinach. This study can provide a basis for the application of fillers and biosorbents in the treatment of biogas slurry in livestock and poultry farms in wetlands.

Evaluation of phosphate adsorption on zirconium/magnesium-modified bentonite

In this work, a zirconium/magnesium-modified bentonite (ZrMgBT) was prepared and characterized by SEM, EDS, XRD and pH_PZC. The performance and mechanism of phosphate adsorption onto ZrMgBT was evaluated in detail using batch experiments and ³¹P NMR. Results showed the adsorption isotherm data were well described by the Langmuir, Freundlich and Dubinin-Radushkevich models, and the kinetic data fitted better to the pseudo-second-order kinetic model than the pseudo-first-order kinetic model. The phosphate adsorption capacity of ZrMgBT was slightly affected by the presence of Na⁺, K⁺, Cl^-, [Formula: see text] and [Formula: see text], but it was enhanced by coexisting Mg²⁺ and [Formula: see text]. The mechanism for phosphate adsorption onto ZrMgBT at pH 7 was mainly the complexation reaction between phosphate and zirconium. In addition, ZrMgBT exhibited more excellent adherence to phosphate than zirconium-modified bentonite (ZrBT). Especially, the maximum monolayer phosphate adsorption capacity for ZrMgBT at pH 7 and 0.5 g/L of adsorbent dosage calculated based on the Langmuir isotherm model (13.0 mg P/g) was 67.5% higher than that for ZrBT. The higher phosphate adsorption capacity for ZrMgBT than ZrBT could be attributed to the higher specific surface area as well as higher Mg²⁺ releasing ability of the former. The enhancement of phosphate adsorption by the release of Mg²⁺ from ZrMgBT could be mainly due to the formation of [Formula: see text] in the solution firstly and then the adsorption of [Formula: see text] on ZrMgBT forming ≡Zr(OPO₃H)Mg on the ZrMgBT surface. In general, we conclude that ZrMgBT is a more promising adsorbent for phosphate removal from aqueous solution than ZrBT.

Co-precipitative Preparation of a Sulfonated Cellulose-magnetite Hybrid Sorbent for the Removal of Cu2+ Ions

A novel sulfonated cellulose-magnetite (Fe3O4) composite sorbent was prepared and applied for the removal of Cu2+ ions from an aqueous solution. It was characterized by infrared spectroscopy, X-ray fluorescence, elemental analysis, SEM, VSM and X-ray photoelectron spectroscopy. The effect of the sorbent dose, initial solution pH, and temperature on Cu2+ removal were studied. The removal of the Cu2+ was completed in 15 min, and the sorption kinetics of Cu2+ was found to follow a pseudo-second-order kinetic model. An equilibrium test demonstrated that sorption of Cu2+ onto a hybrid sorbent agreed well with the Langmuir adsorption model for a maximum adsorption capacity of 4.2 mg/g. Moreover, the optimum pH for Cu2+ removal was found to be ≥4. Furthermore, the thermodynamic parameters reveal the feasibility, spontaneity and endothermic nature of the sorption process. In addition, Cu2+ ions can be desorbed from the sorbent with a 0.5 M H2SO4 solution.

Enhanced interlayer trapping of Pb(II) ions within kaolinite layers: intercalation, characterization, and sorption studies

Lead (Pb(II)) pollution in water poses a serious threat to human health in many parts of the world. In the past decades, research has been aimed at developing efficient and cost-effective methods to address the problem. In this study, dimethyl sulfoxide (DMSO) and potassium acetate (K-Ac) intercalated kaolinite complexes were synthesized and subsequently utilized for Pb(II) removal from water. The intercalation of kaolinite with DMSO was found to be useful for expanding the interlayer space of the clay mineral from 0.72 to 1.12 nm. Kaolinite intercalation with K-Ac (KDK) increased the interlayer space from 1.12 to 1.43 nm. The surface area of KDK was found to be more than threefold higher as compared to natural kaolinite (NK). Batch experimental results revealed that the maximum Pb(II) uptake capacity of KDK was 46.45 mg g^-1 which was higher than the capacity of NK (15.52 mg g^-1). Reusability studies showed that KDK could be reused for 5 cycles without substantially losing its adsorption capacity. Furthermore, fixed-bed column tests confirmed the suitability of KDK in continuous mode for Pb(II) removal. Successful application of intercalated kaolinite for Pb(II) adsorption in batch and column modes suggests its application in water treatment (especially removal of divalent metals).

Synthesis, Characterization, Kinetics, and Thermodynamics of EDTA-Modified Chitosan-Carboxymethyl Cellulose as Cu(II) Ion Adsorbent

A new adsorbent derived from the naturally occurring biopolymers, chitosan (CS) and carboxymethyl cellulose (CMC) was prepared by cross-linking them using EDTA. EDTA having high affinity for metal ions can be used to enhance the chelation properties of the adsorbent enormously. The product obtained (chitosan-EDTA-CMC, CSECM) was characterized by different techniques: FTIR, XRD, SEM/EDAX, TGA, and XPS. The parameters for evaluation of the adsorption properties for removal of Cu(II) ions from the aqueous solution were determined using the batch adsorption method by studying the effect of pH, contact time, initial ion concentration, and temperature on adsorption. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic models were applied to study the kinetics of the adsorption process, whereas Langmuir, Freundlich, Temkin, and D-R models were applied to evaluate the thermodynamics of the adsorption process. The kinetic adsorption parameters were in best agreement with the pseudo-second-order model, while thermodynamic parameters best fitted to the Langmuir isotherm at different temperatures for adsorption of Cu(II) ions from aqueous solution with a maximum adsorption capacity of 142.95 mg/g at pH 5.5. CSECM showed excellent regeneration capability and recovery of the Cu(II) ion up to five cycles without the loss of the adsorption efficiency, which is the best characteristic to select the appropriate choice of the adsorbent. The adsorbent was also employed in batch experiments to evaluate the adsorption of hardness, producing common metal ions in single and real wastewater solutions.

Technologies applicable to the removal of heavy metals from landfill leachate

This article presents a review of the main physical, chemical, electrochemical, and biological technologies used for treating heavy metals in the wastewater of industrial processes and in synthetic aqueous solutions which could be applied to leachate from landfills. This paper outlines the generalities, operating principles, and modifications made to the technologies described. It discusses and assesses which of these have better removal rates and higher levels of efficiency in minimizing the heavy metal concentrations contained in leachates, such as mercury, chromium, lead, nickel, and copper among others. The first part of the document presents the so-called conventional technologies, such as chemical, physical, and electrochemical treatment. These have been used to treat different wastewater, especially industrial waste, operating adequately from the technical topic, but with high costs and the secondary products' production. The second part exposes biological treatments tend to be most widely used due to their versatility, effectiveness, and low cost, when compared with traditional technologies. It is important to note that there is no single treatment and that each of the technologies reviewed has different heavy metal decontamination rates. All technologies search to reduce concentrations of heavy metals to values that are safe for the natural resources where they are discharged or disposed, thereby complying with the regulatory limits regulated in each of the regions.

Environmental remediation of heavy metal ions by novel-nanomaterials: A review

Recently, novel-nanomaterials with excellent sorption capacities, mild stability, and environmental-friendly performance, have enabled massive developments in capturing heavy metal ions. This review firstly introduces the preparation and modification of novel-nanomaterials (e.g., MOFs, nZVI, MXenes, and g-C₃N₄). Then, the heavy metal ions' sorption properties and the impact of environmental conditions have been discussed. Subsequently, the sorption mechanisms are verified through batch experiments, spectral analysis, surface complexation models, and theoretical calculations. Finally, the applications prospects of novel-nanomaterials in removing heavy metal ion polluted water have also been discussed, which provide perspective for future in-depth research and practical applications.