Adsorption of heavy metals on conventional and nanostructured materials for wastewater treatment purposes: A review

The problem of water pollution is of a great concern. Adsorption is one of the most efficient techniques for removing noxious heavy metals from the solvent phase. This paper presents a detailed information and review on the adsorption of noxious heavy metal ions from wastewater effluents using various adsorbents - i.e., conventional (activated carbons, zeolites, clays, biosorbents, and industrial by-products) and nanostructured (fullerenes, carbon nanotubes, graphenes). In addition to this, the efficiency of developed materials for adsorption of the heavy metals is discussed in detail along with the comparison of their maximum adsorption capacity in tabular form. A special focus is made on the perspectives of further wider applications of nanostructured adsorbents (especially, carbon nanotubes and graphenes) in wastewater treatment.

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

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

Health impacts of environmental contamination of micro- and nanoplastics: a review

Plastics are extensively used in our daily life. However, a significant amount of plastic waste is discharged to the environment directly or via improper reuse or recycling. Degradation of plastic waste generates micro- or nano-sized plastic particles that are defined as micro- or nanoplastics (MNPs). Microplastics (MPs) are plastic particles with a diameter less than 5 mm, while nanoplastics (NPs) range in diameter from 1 to 100 or 1000 nm. In the current review, we first briefly summarized the environmental contamination of MNPs and then discussed their health impacts based on existing MNP research. Our review indicates that MNPs can be detected in both marine and terrestrial ecosystems worldwide and be ingested and accumulated by animals along the food chain. Evidence has suggested the harmful health impacts of MNPs on marine and freshwater animals. Recent studies found MPs in human stool samples, suggesting that humans are exposed to MPs through food and/or drinking water. However, the effect of MNPs on human health is scarcely researched. In addition to the MNPs themselves, these tiny plastic particles can release plastic additives and/or adsorb other environmental chemicals, many of which have been shown to exhibit endocrine disrupting and other toxic effects. In summary, we conclude that more studies are necessary to provide a comprehensive understanding of MNP pollution hazards and also provide a basis for the subsequent pollution management and control.

A review of the mycotoxin adsorbing agents, with an emphasis on their multi-binding capacity, for animal feed decontamination

Contamination of animal feed with mycotoxins still occurs very often, despite great efforts in preventing it. Animal feeds are contaminated, at low levels, with several mycotoxins, particularly with those produced by Aspergillus and Fusarium genera (Aflatoxin B_1, Ochratoxin A, Zearalenone, Deoxynivalenol and Fumonisina B₁). In animal feed, to date, only Aflatoxin B₁ is limited through EU regulation. Consequently, mycotoxins cause serious disorders and diseases in farm animals. In 2009, the European Union (386/2009/EC) approved the use of mycotoxin-detoxifying agents, as feed additives, to prevent mycotoxicoses in farm animals. The present review gives an overview of the problem of multi-mycotoxin contamination of feed, and aims to classify mycotoxin adsorbing agents (minerals, organic, and synthetic) for feed decontamination, focusing on adsorbents with the ability to bind to multiple mycotoxins, which should have a more effective application in farms but they are still little studied in scientific literature.

Novel fungus-Fe3O4 bio-nanocomposites as high performance adsorbents for the removal of radionuclides

The bio-nanocomposites of fungus-Fe3O4 were successfully synthesized using a low-cost self-assembly technique. SEM images showed uniform decoration of nano-Fe3O4 particles on fungus surface. The FTIR analysis indicated that nano-Fe3O4 was combined to the fungus surface by chemical bonds. The sorption ability of fungus-Fe3O4 toward Sr(II), Th(IV) and U(VI) was evaluated by batch techniques. Radionuclide sorption on fungus-Fe3O4 was independent of ionic strength, indicating that inner-sphere surface complexion dominated their sorption. XPS analysis indicated that the inner-sphere radionuclide complexes were formed by mainly bonding with oxygen-containing functional groups (i.e., alcohol, acetal and carboxyl) of fungus-Fe3O4. The maximum sorption capacities of fungus-Fe3O4 calculated from Langmuir isotherm model were 100.9, 223.9 and 280.8 mg/g for Sr(II) and U(VI) at pH 5.0, and Th(IV) at pH 3.0, respectively, at 303 K. Fungus-Fe3O4 also exhibited excellent regeneration performance for the preconcentration of radionuclides. The calculated thermodynamic parameters showed that the sorption of radionuclides on fungus-Fe3O4 was a spontaneous and endothermic process. The findings herein highlight the novel synthesis method of fungus-Fe3O4 and its high sorption ability for radionuclides.

Removal of natural organic matter (NOM) and its constituents from water by adsorption - A review

Natural organic matter (NOM) is produced through metabolic reactions in water supply in drinking water sources and has been reported to cause several problems including objectionable taste and color of water, formation of disinfection by-products (DBPs) and reducing the amount of dissolved oxygen in water. The removal of NOM and its constituents from water is a challenging issue worldwide. Many technologies have been examined for this purpose. The properties and amount of NOM, however, can significantly affect the process efficiency. In the present work, an overview of the recent research studies dealing with adsorption method for the removal of NOM and related compounds from water is presented. A wide variety of conventional and non-conventional adsorbents have been reviewed for their potential in NOM removal from water. As revealed from the literature reviewed, modified adsorbents, composite materials and few nanomaterials have shown promising results for NOM removal from water. The main findings obtained for the removal of NOM using different adsorbents have been discussed in this review.

A review on agro-industrial waste (AIW) derived adsorbents for water and wastewater treatment

There is a large amount of studies surrounding the usage of agro-industrial waste (AIW) for the adsorptions of organic pollutants (dyes) and inorganic pollutants (heavy metals) in water/wastewater. This method is normally treated as an alternative approach to the conventional water/wastewater treatment. However, there are some increasing interests for investigators to identify novel adsorption materials for pollutants removal. It is particularly noteworthy that most AIW wastes are not currently used at the original state, but modified in a variety of ways to reinforce the porosity and adsorption surface area of the material. Nanostructuring, activation, carbonization, and grafting are some common modification technologies of agricultural waste adsorbents. Besides, the characteristic, preparation and application of adsorbents from various industrial wastes, including natural materials and biosorbents, were summarized. Additionally, the challenges and perspectives for future researches of waste-derived adsorbents were studied. This review provides an important insight on using AIWs as precursor materials for preparing adsorbents in water/wastewater treatment.

La(OH)3-modified magnetic pineapple biochar as novel adsorbents for efficient phosphate removal

A series of La(OH)₃-modified magnetic pineapple biochar (Lax-MC) with different contents of La(OH)₃ were prepared and used as phosphate adsorbents for the first time. With the increase of La(OH)₃ content, the adsorption capacity for phosphate increased while the magnetic property decreased. La10-MC exhibited excellent magnetic property for easy recovery and high adsorption capacity up to 101.16 mg P/g, which was 27 times that of pineapple biochar and much higher than most phosphate adsorbents. Adsorption isotherm and adsorption kinetics were better fitted by Langmuir model and pseudo second-order model, respectively. The removal efficiency >96.04% in coexisting ions indicated its high selectivity to phosphate. Little decrease in removal efficiency after three adsorption-desorption cycles suggested its excellent stability and cyclic utilization. Leaching study demonstrated the negligible risk of La³⁺ and Fe³⁺ leakage during adsorption process. Mechanism study revealed that the adsorption mechanism involved precipitation, electrostatic interaction, ligand exchange and inner-sphere complexation.

Application of polyaniline-based adsorbents for dye removal from water and wastewater-a review

Several industries release varying concentration of dye-laden effluent with substantial negative consequences for any receiving environmental compartment. The control of water pollution and tighter restriction on wastewater discharge directly into the environment to reduce the potential ecotoxicological effect of dyes is forcing processors to retreat and reuse process water and chemicals. Among the different available technologies, the adsorption process has been recognized to be one of the finest and cost-effective wastewater treatment technologies. Various adsorbents have been utilized to remove toxic dyes from water and wastewater. Here, we review the application of polyaniline-based polymeric adsorbent for the adsorption of dyes which have been received considerable attention. To date, various modifications of polyaniline have been explored to improve the adsorption properties. Review on the application of polyaniline for adsorption of dyes has not been present till date. This article provides relevant literature on the application of various polyaniline composites for removing dyes, and their adsorption capacities with their experimental conditions have been compiled. It is evident from the literature survey that polyaniline provides a better opportunity for scientists for the effective removal of various dye.

Environmental applications of chitosan and cellulosic biopolymers: A comprehensive outlook

Biopolymers are substances naturally produced by living organisms and are hence considered to be eco-friendly and sustainable. Chitosan and cellulose are of specific significance owing to their abundant availability, ease of modification, and application potential. On the environmental front, their coagulating and flocculating effects have helped in wastewater clarification, while minimizing the dependability on synthetic polyelectrolytes. Biopolymer based hydrogels and nanocomposite films have functioned as effective biosorbents in removing an array of organic and inorganic pollutants, including xenobiotics, from wastewater. Specifically, they have been vastly harnessed for heavy metal and dye adsorption. They have also played a pivotal part in other environmental applications including anti-desertification, natural bio-sealants for preventing concrete leaks and proton conducting membranes in electrochemical devices. Such recent research on the environmental applications of biopolymers has been comprehensively analysed, thus providing a fresh insight into the future prospects of research in this domain.

Porous carriers for controlled/modulated drug delivery

Considerable research efforts have been directed in recent years towards the development of porous carriers as controlled drug delivery matrices because of possessing several features such as stable uniform porous structure, high surface area, tunable pore size and well-defined surface properties. Owing to wide range of useful properties porous carriers have been used in pharmaceuticals for many purposes including development of floating drug delivery systems, sustained drug delivery systems. Various types of pores like open, closed, transport and blind pores in the porous solid allow them to adsorb drugs and release them in a more reproducible and predictable manner. Pharmaceutically exploited porous adsorbents includes, silica (mesoporous), ethylene vinyl acetate (macroporous), polypropylene foam powder (microporous), titanium dioxide (nanoporous). When porous polymeric drug delivery system is placed in contact with appropriate dissolution medium, release of drug to medium must be preceded by the drug dissolution in the water filled pores or from surface and by diffusion through the water filled channels. The porous carriers are used to improve the oral bioavailability of poorly water soluble drugs, to increase the dissolution of relatively insoluble powders and conversion of crystalline state to amorphous state.

Recovery, regeneration and sustainable management of spent adsorbents from wastewater treatment streams: A review

Adsorption is the most widely adopted, effective, and reliable treatment process for the removal of inorganic and organic contaminants from wastewater. One of the major issues with the adsorption-treatment process for the removal of contaminants from wastewater streams is the recovery and sustainable management of spent adsorbents. This review focuses on the effectiveness of emerging adsorbents and how the spent adsorbents could be recovered, regenerated, and further managed through reuse or safe disposal. The critical analysis of both conventional and emerging adsorbents on organic and inorganic contaminants in wastewater systems are evaluated. The various recovery and regeneration techniques of spent adsorbents including magnetic separation, filtration, thermal desorption and decomposition, chemical desorption, supercritical fluid desorption, advanced oxidation process and microbial assisted adsorbent regeneration are discussed in detail. The current challenges for the recovery and regeneration of adsorbents and the methodologies used for solving those problems are covered. The spent adsorbents are managed through regeneration for reuse (such as soil amendment, capacitor, catalyst/catalyst support) or safe disposal involving incineration and landfilling. Sustainable management of spent adsorbents, including processes involved in the recovery and regeneration of adsorbents for reuse, is examined in the context of resource recovery and circular economy. Finally, the review ends with the current drawbacks in the recovery and management of the spent adsorbents and the future directions for the economic and environmental feasibility of the system for industrial-scale application.

Supported and unsupported nanomaterials for water and soil remediation: are they a useful solution for worldwide pollution?

Remediation technologies for wastes generated by industrial processes include coagulation, reverse osmosis, electrochemistry, photoelectrochemistry, advanced oxidation processes, and biological methods, among others. Adsorption onto activated carbon, sewage sludge, zeolites, chitosan, silica, and agricultural wastes has shown potential for pollutants' removal from aqueous media. Recently, nanoscale systems [nanoparticles (NPs) supported on different inorganic adsorbents] have shown additional benefits for the removal/degradation of several contaminants. According to the literature, NPs enhance the adsorption capacity of adsorbent materials and facilitate degradation of pollutants through redox reactions. In this review we analyzed relevant literature from 2011 to 2013, dealing with water and soil remediation by nanomaterials (NMs), either unsupported or supported upon inorganic adsorbents. Despite the outstanding reported results for some NMs, the analysis of the literature makes clear the necessity of more studies. There is lack of information about NMs regeneration and reusability, their large-scale application, and their efficiency in actual industrial wastewaters and contaminated soils. Additionally, little is known about NMs' life cycle, release of metal ions, disposal of pollutant loaded NMs, and their impacts on different ecosystems.

Metal-organic frameworks for aquatic arsenic removal

Effective remediation of arsenic contaminated water remains a critical task from the environmental perspective, owing to the harmful effects of arsenic on human health and the environment. Recently, highly porous metal-organic frameworks (MOFs) with excellent chemical stability and abundant functional groups represent a significant new addition to the area of capturing aquatic arsenic pollutants. This review focuses on the development of MOF-based materials for the efficient removal of toxic arsenic species from aqueous solutions. Aspects related to the materials' characteristics, application performance and interaction mechanisms are systematically studied, referencing the macroscopic experimental behaviors and microscopic spectroscopy analyses. The properties of various MOF-based materials are assessed and compared with those of other conventionally used materials. At last, insights and perspectives are suggested in terms of future research directions and development challenges. Overall, this class of materials demonstrates a promising potential for aquatic arsenic removal, and with a proper up-scaling development might it be used for practical applications in the near future.

Heavy metal removal by biomass-derived carbon nanotubes as a greener environmental remediation: A comprehensive review

The concentrations of heavy metal ions found in waterways near industrial zones are often exceed the prescribed limits, posing a continued danger to the environment and public health. Therefore, greater attention has been devoted into finding the efficient solutions for adsorbing heavy metal ions. This review paper focuses on the synthesis of carbon nanotubes (CNTs) from biomass and their application in the removal of heavy metals from aqueous solutions. Techniques to produce CNTs, benefits of modification with various functional groups to enhance sorption uptake, effects of operating parameters, and adsorption mechanisms are reviewed. Adsorption occurs via physical adsorption, electrostatic interaction, surface complexation, and interaction between functional groups and heavy metal ions. Moreover, factors such as pH level, CNTs dosage, duration, temperature, ionic strength, and surface property of adsorbents have been identified as the common factors influencing the adsorption of heavy metals. The oxygenated functional groups initially present on the surface of the modified CNTs are responsible towards the adsorption enhancement of commonly-encountered heavy metals such as Pb²⁺, Cu²⁺, Cd²⁺, Co²⁺, Zn²⁺, Ni²⁺, Hg²⁺, and Cr⁶⁺. Despite the recent advances in the application of CNTs in environmental clean-up and pollution treatment have been demonstrated, major obstacles of CNTs such as high synthesis cost, the agglomeration in the post-treated solutions and the secondary pollution from chemicals in the surface modification, should be critically addressed in the future studies for successful large-scale applications of CNTs.

3D-Printed metal-organic frameworks within biocompatible polymers as excellent adsorbents for organic dyes removal

Three-dimensional (3D) printing technique has received exceptional global attention as it can create a myriad of high-resolution architectures from digital models. In the present study, 3D-printed metal-organic frameworks (MOFs) were shaped into several geometries via direct ink writing, which overcomes the instability and high-pressure drop of powdery MOF during the flow of gas or liquid streams. The inclusion of a blend of calcium alginate and gelatin (CA-GE) as biocompatible binder allowed for easy writing and an enhanced mechanical property. Besides, it was found that the printing geometry (square, hexagon, and circle), MOF loading amount, and MOF size also greatly influenced the adsorptive performance. For instance, the methylene blue adsorption efficiency of CA-GE scaffolds without MOF was only 43.6%, while the printed MOF/CA-GE sample exhibited 99.8% adsorption efficiency at 20 min. Both the inherent microporous structure of MOFs and meso/macroporous structures of the 3D matrix contributed to the excellent adsorption properties towards a variety of organic dyes and their mixtures. Furthermore, the 3D-printed adsorbents can be easily regenerated in dilute acid solution and reused for at least 7 times without performance loss. In contrast, the powdery MOF can only be repeatedly used for at most 2 times.

Polyaniline-based adsorbents for removal of hexavalent chromium from aqueous solution: a mini review

Hexavalent chromium (Cr(VI)) is a common hazardous contaminant in the environment and carcinogenic or mutagenic to aquatic animals and human beings. Therefore, the removal and detoxification of Cr(VI) have been attracting increasing attention of researchers. Among various conducting polymers, polyaniline (PANI)-based adsorbents have shown an excellent performance on the removal of Cr(VI) because of their redox properties, eased synthesis, and favorable biocompatibility. In this review, the characteristics of various PANI-based adsorbents were described, including PANI-modified nanofiber mats and membranes, PANI/bio-adsorbents, PANI/magnetic adsorbents, PANI/carbon adsorbents, PANI-modified clay composites, and PANI-inorganic hybrid composites. The mechanisms for the detoxification and adsorption of Cr(VI) were also discussed. The results indicated the potential applications of PANI-based adsorbents for the removal of Cr(VI). Graphical abstract ᅟ.

Sources, toxicity, and remediation of mercury: an essence review

Mercury (Hg) is a pollutant that poses a global threat, and it was listed as one of the ten leading 'chemicals of concern' by the World Health Organization in 2017. The review aims to summarize the sources of Hg, its combined effects on the ecosystem, and its remediation in the environment. The flow of Hg from coal to fly ash (FA), soil, and plants has become a serious concern. Hg chemically binds to sulphur-containing components in coal during coal formation. Coal combustion in thermal power plants is the major anthropogenic source of Hg in the environment. Hg is taken up by plant roots from contaminated soil and transferred to the stem and aerial parts. Through bioaccumulation in the plant system, Hg moves into the food chain, resulting in potential health and ecological risks. The world average Hg concentrations reported in coal and FA are 0.01-1 and 0.62 mg/kg, respectively. The mass of Hg accumulated globally in the soil is estimated to be 250-1000 Gg. Several techniques have been applied to remove or minimize elevated levels of Hg from FA, soil, and water (soil washing, selective catalytic reduction, wet flue gas desulphurization, stabilization, adsorption, thermal treatment, electro-remediation, and phytoremediation). Adsorbents such as activated carbon and carbon nanotubes have been used for Hg removal. The application of phytoremediation techniques has been proven as a promising approach in the removal of Hg from contaminated soil. Plant species such as Brassica juncea are potential candidates for Hg removal from soil.

Potential utility of graphene-based nano spinel ferrites as adsorbent and photocatalyst for removing organic/inorganic contaminants from aqueous solutions: A mini review

Toxic substances such as heavy metals or persistent organic pollutants raise global environmental concerns. Thus, diverse water decontamination approaches using nano-adsorbents and/or photocatalysts based on nanotechnology are being developed. Particularly, many studies have examined the removal of organic and inorganic contaminants with novel graphene-based nano spinel ferrites (GNSFs) as potential cost-effective alternatives to traditionally used materials, owing to their enhanced physical and chemical properties. The introduction of magnetic spinel ferrites into 2-D graphene-family nanomaterials to form GNSFs brings various benefits such as inhibited particle agglomeration, enhanced active surface area, and easier magnetic separation for reuse, making the GNSFs highly efficient and eco-friendly materials. Here, we present a short review on the state-of-the-art progresses on developments of GNSFs, as well as their potential application for removing several recalcitrant contaminants including organic dyes, antibiotics, and heavy metal ions. Particularly, the mechanisms involved in the adsorptive and photocatalytic degradation are thoroughly reviewed, and the reusability of the GNSFs is also highlighted. This review concludes that the GNSFs hold great potential in remediating contaminated aquatic environments. Further studies are needed for their practical and large-scale applications.

Poly(acryloyl hydrazide)-grafted cellulose nanocrystal adsorbents with an excellent Cr(VI) adsorption capacity

In this study, we prepared poly(acryloyl hydrazide) (PAH)-grafted cellulose nanocrystal (CNC-PAH) particles via the atom transfer radical polymerization method for application to Cr(VI) adsorption. The closely-packed PAH chains grafted on the cellulose nanocrystal (CNC) surface provide a high density of amine groups that can adsorb Cr(VI) through strong electrostatic, hydrogen bonding and chelating interactions. CNC-PAH exhibited the optimum Cr(VI) adsorption capacity at the solution pH = 3, where its electrostatic attraction with Cr(VI) was maximized. Cr(VI) was chemisorbed in CNC-PAH by following the Langmuir isotherm mechanism (homogeneous monolayer adsorption). The Cr(VI) adsorption kinetics of CNC-PAH was controlled predominantly by intra-particle diffusion resistance imparted by the PAH shell layer. Thermodynamic analysis revealed that Cr(VI) adsorption of CNC-PAH is a spontaneous and endothermic process. Importantly, CNC-PAH grafted with the higher M_w (∼50 kg mol^-1) PAH exhibited a rapid Cr(VI) adsorption rate and remarkably high Cr(VI) adsorption capacity (∼457.6 mg g^-1 at 298.15 K), exceeding those of previously reported adsorbents owing to its numerous Cr(VI)-adsorptive amine groups provided by the closely-packed grafted PAH polymers. Furthermore, CNC-PAH showed excellent reusability to maintain its high adsorption ability during repeated adsorption-desorption cycles owing to the covalently binding nature of the PAH polymers.

Cyclodextrin-based adsorbents for the removal of pollutants from wastewater: a review

Water is a vital substance that constitutes biological structures and sustains life. However, water pollution is currently among the major environmental challenges and has attracted increasing study attention. How to handle contaminated water now mainly focuses on removing or reducing the pollutants from the wastewater. Cyclodextrin derivatives, possessing external hydrophilic and internal hydrophobic properties, have been recognized as new-generation adsorbents to exert positive effects on water pollution treatment. This article outlines recent contributions of cyclodextrin-based adsorbents on wastewater treatment, highlighting different adsorption mechanisms of cyclodextrin-based adsorbents under different influencing factors. The crosslinked and immobilized cyclodextrin-based adsorbents all displayed outstanding adsorption capacities. Particularly, according to specific pollutants including metal ions, organic chemicals, pesticides, and drugs in wastewater, this article has classified and organized various cyclodextrin-based adsorbents into tables, which could pave an intuitive shortcut for designing and developing efficient cyclodextrin-based adsorbents for targeted wastewater pollutants. Besides, this article specially discusses cost-effectiveness and regeneration performance of current cyclodextrin-based adsorbents. Finally, the challenges and future directions of cyclodextrin-based adsorbents are prospected in this article, which may shed substantial light on practical industrial applications of cyclodextrin-based adsorbents.

Removal of mercury by adsorption: a review

Due to natural and production activities, mercury contamination has become one of the major environmental problems over the world. Mercury contamination is a serious threat to human health. Among the existing technologies available for mercury pollution control, the adsorption process can get excellent separation effects and has been further studied. This review is attempted to cover a wide range of adsorbents that were developed for the removal of mercury from the year 2011. Various adsorbents, including the latest adsorbents, are presented along with highlighting and discussing the key advancements on their preparation, modification technologies, and strategies. By comparing their adsorption capacities, it is evident from the literature survey that some adsorbents have shown excellent potential for the removal of mercury. However, there is still a need to develop novel, efficient adsorbents with low cost, high stability, and easy production and manufacture for practical utility.

Treatment of model and galvanic waste solutions of copper(II) ions using a lignin/inorganic oxide hybrid as an effective sorbent

A study was made concerning the removal of copper(II) ions from model and galvanic waste solutions using a new sorption material consisting of lignin in combination with an inorganic oxide system. Specific physicochemical properties of the material resulted from combining the activity of the functional groups present in the structure of lignin with the high surface area of the synthesized oxide system (585m²/g). Analysis of the porous structure parameters, particle size and morphology, elemental composition and characteristic functional groups confirmed the effective synthesis of the new type of sorbent. A key element of the study was a series of tests of adsorption of copper(II) ions from model solutions. It was determined how the efficiency of the adsorption process was affected by the process time, mass of sorbent, concentration of adsorbate, pH and temperature. Potential regeneration of adsorbent, which provides the possibility of its reusing and recovering the adsorbed copper, was also analyzed. The sorption capacity of the material was measured (83.98mg/g), and the entire process was described using appropriate kinetic models. The results were applied to the design of a further series of adsorption tests, carried out on solutions of real sewage from a galvanizing plant.

Remediation of emerging environmental pollutants: A review based on advances in the uses of eco-friendly biofabricated nanomaterials

The increased environmental pollutants due to anthropogenic activities are posing an adverse effects and threat on various biotic forms on the planet. Heavy metals and certain organic pollutants by their toxic persistence in the environment are regarded as significant pollutants worldwide. In recent years, pollutants exist in various forms in the environment are difficult to eliminate by traditional technologies due to various drawbacks. This has lead to shifting of research for the development of cost-effective and efficient technologies for the remediation of environmental pollutants. The adaption of adsorption phenomenon from the traditional technologies with the modification of adsorbents at nanoscale is the trended research for mitigating the environmental pollutants with petite environmental concerns. Over the past decade, the hidden potentials of biological sources for the biofabrication of nanomaterials as bequeathed rapid research for remediating the environmental pollution in a sustainable manner. The biofabricated nanomaterials possess an inimitable phenomenon such as photo and enzymatic catalysis, electrostatic interaction, surface active site interactions, etc., contributing for the detoxification of various pollutants. With this background, the current review highlights the emerging biofabricated nano-based adsorbent materials and their underlying mechanisms addressing the environmental remediation of persistent organic pollutants, heavy metal (loid)s, phytopathogens, special attention to the reduction of pathogen-derived toxins and air pollutants. Each category is illustrated with suitable examples, fundamental mechanism, and graphical representations, along with societal applications. Finally, the future and sustainable development of eco-friendly biofabricated nanomaterial-based adsorbents is discussed.

A review of PFAS adsorption from aqueous solutions: Current approaches, engineering applications, challenges, and opportunities

Per- and polyfluoroalkyl substances (PFAS) have drawn great attention due to their wide distribution in water bodies and toxicity to human beings. Adsorption is considered as an efficient treatment technique for meeting the increasingly stringent environmental and health standards for PFAS. This paper systematically reviewed the current approaches of PFAS adsorption using different adsorbents from drinking water as well as synthetic and real wastewater. Adsorbents with large mesopores and high specific surface area adsorb PFAS faster, their adsorption capacities are higher, and the adsorption process are usually more effective under low pH conditions. PFAS adsorption mechanisms mainly include electrostatic attraction, hydrophobic interaction, anion exchange, and ligand exchange. Various adsorbents show promising performances but challenges such as requirements of organic solvents in regeneration, low adsorption selectivity, and complicated adsorbent preparations should be addressed before large scale implementation. Moreover, the aid of decision-making tools including response surface methodology (RSM), techno-economic assessment (TEA), life cycle assessment (LCA), and multi criteria decision analysis (MCDA) were discussed for engineering applications. The use of these tools is highly recommended prior to scale-up to determine if the specific adsorption process is economically feasible and sustainable. This critical review presented insights into the most fundamental aspects of PFAS adsorption that would be helpful to the development of effective adsorbents for the removal of PFAS in future studies and provide opportunities for large-scale engineering applications.