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The release of pharmaceuticals into the environment induces adverse effects on the metabolism of humans and other living species, calling for advanced remediation methods. Conventional removal methods are often non-selective and cause secondary contamination. These issues may be partly solved by the use of recently-developped adsorbents such as molecularly imprinted polymers. Here we review the synthesis and application of molecularly imprinted polymers for removing pharmaceuticals in water. Molecularly imprinted polymers are synthesized via several multiple-step polymerization methods. Molecularly imprinted polymers are potent adsorbents at the laboratory scale, yet their efficiency is limited by template leakage and polymer quality. Adsorption performance of multi-templated molecularly imprinted polymers depends on the design of wastewater treatment plants, pharmaceutical consumption patterns and the population serviced by these wastewater treatment plants.

Pure water will become a golden resource in the context of the rising pollution, climate change and the recycling economy, calling for advanced purification methods such as the use of nanostructured adsorbents. However, coming up with an ideal nanoadsorbent for micropollutant removal is a real challenge because nanoadsorbents, which demonstrate very good performances at laboratory scale, do not necessarily have suitable properties in in full-scale water purification and wastewater treatment systems. Here, magnetic nanoadsorbents appear promising because they can be easily separated from the slurry phase into a denser sludge phase by applying a magnetic field. Yet, there are only few examples of large-scale use of magnetic adsorbents for water purification and wastewater treatment. Here, we review magnetic nanoadsorbents for the removal of micropollutants, and we explain the integration of magnetic separation in the existing treatment plants. We found that the use of magnetic nanoadsorbents is an effective option in water treatment, but lacks maturity in full-scale water treatment facilities. The concentrations of magnetic nanoadsorbents in final effluents can be controlled by using magnetic separation, thus minimizing the ecotoxicicological impact. Academia and the water industry should better collaborate to integrate magnetic separation in full-scale water purification and wastewater treatment plants.

The access to clean water is a critical issue in the context of climate change and worldwide pollution, calling for advanced methods of purification. Recent advances in materials science, nanoscience, and analytical chemistry have led to the design of novel nanoadsorbents having a unique properties, structure, and adsorption performances. In particular, research has focused on all-inclusive adsorbents which can remove different contaminants simultaneously. Here, we review the adsorption dynamics of doped, ionic liquid-enhanced, bio-based, and chemically functionalized materials. We examine their characteristics, underlying principles of adsorption, and their potential limitations in adsorbing various metal ions and xenobiotics. We found that chemical functionalization with specific organic moieties is a preferred approach for enhancing the adsorption capacities and selectivity of raw materials. Moreover, doping can also modulate the morphology, electronic structure, and surface chemistry for higher performance. Ionic liquids are promising solvents for the synthesis of stable adsorbents, owing to ionic liquid ability to pull other molecules through hydrogen bonds or electrostatic forces.

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.

Endosulfan is a highly polluting and toxic pesticide which has been used in many areas globally to control pests in view to improve productivity. Concomitantly, endosulfan has also been associated with many cases of environmental pollution and various types of irreversible metabolic dysfunctions in living organisms both on lands and in waters. Subsequently, since over the last three decades, several endosulfan remediation methods have been studied and many are gradually bringing hope towards efficient clean-up. This article specifically reviews endosulfan degradation and endosulfan removal by discussing the recent findings reported and the trends observed in studies reporting bacterial and fungal bioremediation, photocatalytic degradation, adsorption and membrane separation processes. The salient observations from this review are: there are many bacterial species which degrade endosulfan isomers with relatively high efficiencies; many studies indicate the merits of plants in phytoextracting and accumulating endosulfan but the identification of endosulfan hyperaccumulators remains; photocatalytic systems involving one or two metals also bring about significant endosulfan degradation but issues related with variations in rates of reactions, catalyst deactivation due to fouling, intricacy of metal-based nanocatalyst structures and their complex fabrication methods and lack of control of morphology of the nanosized structures have to be addressed; and membrane retention systems specifically treating endosulfan-contaminated aqueous media are scanty and more analysis is also needed to optimize the shear force-membrane structural integrity-membrane stability rapport of the membranes being developed. In the end, a number of research and development avenues which need further attention and probing towards the development of suitable endosulfan-remediation routes are pointed out. Post-print / Final draft

The release of recalcitrant dyes into the biosphere is a threat because of pollution and environmental health issues. Adsorption using commercial activated carbon has been effective in industrial dye-loaded effluent remediation to some acceptable extent. However, commercial activated carbon suffers from limitations related to cost, relatively lower adsorption capacity, fewer microporous and mesoporous networks in comparison with other competing adsorbents, and reduced adsorption efficiency after regeneration. Here we review the recent developments in applying microwave irradiation, ultrasonication, ionic liquids and nanoscience for the preparation, activation, and physical, chemical and biological functionalization of novel and more potent adsorbents such as metal, mineral, carbon and polymer-based nanoparticles for dye removal. We observed that microwave and ultrasound irradiation and the use of ionic liquids are highly beneficial for the preparation of adsorbent materials; those adsorbents display enhanced porous structures and morphologies that account for much larger surface areas for faster adsorption interactions. Graphene-based, magnetic, cellulose-based and nanocomposite adsorbents are more selective and thermally more stable, faster in dye adsorption kinetics, have higher adsorption capacities for many dyes and can be regenerated for reuse without significant decrease in adsorption capacity. The scales of fabrication of green adsorbents do not go beyond the kilogram scale.

Excess consumption of energy by humans is compounded by environmental pollution, the greenhouse effect and climate change impacts. Current developments in the use of algae for bioenergy production offer several advantages. Algal biomass is hence considered a new bio-material which holds the promise to fulfil the rising demand for energy. Microalgae are used in effluents treatment, bioenergy production, high value added products synthesis and CO2 capture. This review summarizes the potential applications of algae in bioelectrochemically mediated oxidation reactions in fully biotic microbial fuel cells for power generation and removal of unwanted nutrients. In addition, this review highlights the recent developments directed towards developing different types of microalgae MFCs. The different process factors affecting the performance of microalgae MFC system and some technological bottlenecks are also addressed.

Textile effluents in natural waters pose environmental health problems if not treated to safe limits. Various bacterial species have the potential to degrade dyes. Here we studied the ability of Bacillus algicola to decolourise red, blue and yellow azo dyes. B. algicola was isolated from soil samples taken from a sanitary landfill site. Isolation and screening were performed using mineral salt medium. Dye-decolourising isolates were assessed in their capacity to decolourise dyes. Experiments were conducted at pH 6, 7 and 8, and 25, 35 and 45 °C. Phytotoxicity of the dyes and biodegradation products was assessed by seed germination tests. Results show that B. algicola gave the highest decolourisation at pH 8.0 and 25 °C in the presence of yeast extract as media supplement. B. algicola degraded the red and blue azo dyes by over 95%. The phytotoxicity results indicated that biodegradation products of the red and blue azo dyes were not toxic. Biodegradation products of the yellow dye were, however, toxic and considerably hindered germination. From these results, we infer that B. algicola has good potential for degrading and decolourising the red and blue test azo dyes.

The persistence and bioaccumulation of environmental pollutants in water bodies, soils and living tissues remain alarmingly related to environmental protection and ecosystem restoration. Adsorption-based techniques appear highly competent in sequestering several environmental pollutants. In this review, the recent research findings reported on the assessments of composts and compost-amended soils as adsorbents of heavy metal ions, dye molecules and xenobiotics have been appraised. This review demonstrates clearly the high adsorption capacities of composts for umpteen environmental pollutants at the lab-scale. The main inferences from this review are that utilization of composts for the removal of heavy metal ions, dye molecules and xenobiotics from aqueous environments and soils is particularly worthwhile and efficient at the laboratory scale, and the adsorption behaviors and effectiveness of compost-type adsorbents for agrochemicals (e.g. herbicides and insecticides) vary considerably because of variabilities in structure, topology, bond connectivity, distribution of functional groups and interactions of xenobiotics with the active humic substances in composts. Compost-based field-scale remediation of environmental pollutants is still sparse and arguably much challenging to implement if, furthermore, real-world soil and water contamination issues are to be addressed effectively. Hence, significant research and process development efforts should be promptly geared and intensified in this direction by extrapolating the lab-scale findings in a cost-effective manner.

Textile wastewaters contain refractory dyes that cause pollution and socio-economic issues, thus calling for efficient remediation techniques such as photocatalysis. We review the fabrication, functionalization, performance and limitations of doped catalysts for degrading and mineralizing dyes. We present developments in photocatalyst immobilization and photocatalytic reactor design. Methods such as microwave irradiation, sonication and use of ionic liquids are emerging for the preparation of doped photocatalysts. Whilst single-dye systems have been extensively studied, there is limited knowledge on multiple-dye systems. Immobilization of photocatalysts is gaining popularity for large-scale application, but faces issues of erosion, corrosion, mechanical strength and structure integrity. Ecotoxicological studies are required in real environments to validate the potential applications of nanostructured doped photocatalysts.

This paper reports the potential of chemically treated wood chips to remove copper (II) ions from aqueous solution a function of pH, adsorbent dose, initial copper (II) concentration and contact time by batch technique. The wood chips were treated with (a) boiling, (b) formaldehyde and (c) concentrated sulphuric acid and characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive analysis X-ray. pH 5.0 was optimum with 86.1, 88.5 and 93.9 % copper (II) removal by boiled, formaldehyde-treated and concentrated sulphuric acid-treated wood chips, respectively, for dilute solutions at 20 g L−1 adsorbent dose. The experimental data were analysed using Freundlich, Langmuir, Dubinin–Radushkevich and Temkin isotherm models. It was found that Freundlich and Langmuir models fitted better the equilibrium adsorption data and the adsorption process followed pseudo-second-order reaction kinetics. The results showed that the copper (II) is considerably adsorbed on wood chips and it could be an economical option for the removal of copper from aqueous systems.

Heavy metals affect the biochemical reactions that take place during anaerobic digestion processes of organic matter. In this review, the different effects observed in anaerobic digestion processes and during the production of biomethane and biohydrogen from several substrates contaminated with and/or inheriting heavy metals from the substrates themselves were discussed. It has been found that heavy metals exert important roles in biochemical reactions. Heavy metals like copper, nickel, zinc, cadmium, chromium and lead have been overwhelmingly reported to be inhibitory and under certain conditions toxic in biochemical reactions depending on their concentrations. Heavy metals like iron may also exhibit stimulatory effects, but these effects have been scantily observed. This review also concludes that the severity of heavy metal inhibition depends upon factors like metal concentration in a soluble, ionic form in the solution, type of metal species, and amount and distribution of biomass in the digester or chain of biochemical reactions which constitute the anaerobic digestion process. A majority of studies have demonstrated that the toxic effect of heavy metals like chromium, cadmium and nickel is attributable to a disruption of enzyme function and structure by binding of the metal ions with thiol and other groups on protein molecules or by replacing naturally occurring metals in enzyme prosthetic groups. This review has not found published data on the effects of heavy metals on the hydrolysis stage of anaerobic digestion process chemistry, and hence further studies are required to depict any changes.

Industrialization and urbanization have resulted in increased releases of toxic heavy metals into the natural environment comprising soils, lakes, rivers, groundwaters and oceans. Research on biosorption of heavy metals has led to the identification of a number of microbial biomass types that are extremely effective in bioconcentrating metals. Biosorption is the binding and concentration of adsorbate from aqueous solutions by certain types of inactive and dead microbial biomass. The novel types of biosorbents presently reviewed are grouped under fungal biomass, biomass of non-living, dried brown marine algae, agricultural wastes and residues, composite chitosan biosorbent prepared by coating chitosan, cellulose-based sorbents and bacterial strains. The reports discussed in this review collectively suggest the promise of biosorption as a novel and green bioremediation technique for heavy metal pollutants from contaminated natural waters and wastewaters.

Atrazine is a widely used herbicide for controlling weeds on both agricultural and nonagricultural land, which is equally detected in water supplies beyond safe concentrations. Although the presence of atrazine metabolites is an indication of herbicide degradation, some of them still exhibit toxicity, greater water solubility and weaker interaction with soil components than atrazine. Hence, studies with atrazine in the environment are of interest because of its potential to contaminate drinking water sources. Data on atrazine availability for transport, plant uptake, and microbial degradation and mineralization are therefore required to perform more comprehensive and realistic environmental risk assessments of its environmental fate. This review presents an account of the sorption-desorption phenomenon of atrazine on soil and other sorbents by revisiting the several mechanisms of atrazine-sorbent binding reported in the literature. The retention and transport of atrazine in soils; the influence of organic matter on atrazine sorption; the interactions of atrazine with humic substances, atrazine uptake by plants, atrazine bioccumulation and microbial degradation; atrazine transformation in composting environments; and finally atrazine removal by biosorption are discussed.

Arsenic is a toxic element and has been responsible for many accidental, occupational, deliberate, and therapeutic poisonings since its discovery in 1250. It occurs in natural waters as the arsenite (As3+) and arsenate (As5+) ions. The solubility of arsenite and arsenate compounds is relatively high so that these ions are readily transported through aqueous routes into the environment. Arsenic can be transferred from soils to crops and accumulates in various food crops and aquatic plants. The fascinating chemistry and toxicity potential make arsenic and its compounds of particular scientific interest and environmental concern. The conventional removal of heavy metals from wastewater, natural waters, and drinking water has only limited effects on arsenic removal. In this review, the main engineering and medical applications, salient health and environmental concerns, novel research on treatment for arsenic poisoning, and removal technologies for arsenic and their derivatives are discussed and enumerated wi...

The corrosion inhibition and adsorption properties of Neem (Azadirachta indica – AZI) mature leaves extract as a green inhibitor of mild steel (MS) corrosion in nitric acid (HNO3) solutions have been studied using a gravimetric technique for experiments conducted at 30 and 60°C. The results disclose that the different concentrations of the AZI extract inhibit MS corrosion and that inhibition efficiency of the extract varies with concentration and temperature. For extract concentrations studied and ranging from 9.09 to 28.57 mg/L, the maximum inhibition efficiency was 80.5 and 80.07% both at 28.57 mg/L AZI at 30 and 60°C, respectively, in 2.0 N HNO3. The adsorption of the inhibitor on the MS surface was exothermic and consistent with the physical adsorption mechanism, best described by the Frumkin adsorption isotherm.

The corrosion inhibition of Neem (Azadirachta indica (AZI)) leaves extract as a green inhibitor of zinc corrosion in H2SO4 has been studied using the gravimetric method. The results of the study reveal that the different concentrations of the AZI extract inhibit zinc corrosion and that inhibition efficiency of the extract varies with concentration and temperature.

Dioxins and furans are persistent, highly hazardous and ubiquitous compounds that have become the focus of many investigations due to the contamination of food and the ecosystem. Dioxins and furans refer to a class of polyhalogenated aromatic hydrocarbons generated by various chemical processes occurring often at high temperature. The main sources of dioxins and furans have been classified into four categories, namely: incineration, combustion, industrial processes and natural processes such as volcanic eruptions. Dioxins and furans are present in flue gas and fly ash from combustion, in contaminated soils, sediments and water bodies. The expression toxic equivalency (TEQ) factor has been defined to assess their toxicity. Dioxins and furans have adverse effects on human health because they are bioaccumulated in tissues and cells. They are carcinogenic and cause reproductive alterations. They are a threat to the ecosystem because they persist in nature, affecting marine and terrestrial living organisms, and subsequently ending up in the food chain. We review remediation techniques of dioxins and furans. The most common techniques are landfill cap system and deep well injections, high temperature incineration and cement kilns. This chapter focuses on the principal destruction, removal and remediation techniques based on flue gas, fly ash and soil treatment. Basic techniques are selective catalyst reduction technologies, adsorption by means of activated carbon, base catalysed reactions, photolytic degradation processes, thermal desorption processes, alkaline polyethylene glycolate (APEG) process, bioslurry treatment and vitrification.

Industrialization, urbanization and various anthropogenic activities such as mining and agriculture have increased releases of toxic heavy metals into the natural environment such as soils, lakes, rivers, groundwaters and oceans. The release of heavy metals in biologically available forms alter both natural and man–made ecosystems. Although some heavy metal ions are essential micronutrients for plant metabolism, they become highly toxic when they occur at high concentrations in soils, groundwaters and waste streams. Moreover, heavy metals are not biodegradable and persist in the environment. Conventional methods for the removal of the heavy metals ions from contaminated wasters and wastewaters include chemical precipitation, electroflotation, ion exchange, reverse osmosis and adsorption onto activated carbon. Recently, pioneering research on biosorption of heavy metals has led to the identification of microbes that are extremely effective in bioconcentrating metals. Biosorption is the binding and concentration of an element from aqueous solutions by organic materials such as microbial biomass. The major advantages of biosorption over conventional treatment methods include low cost, high efficiency, minimization of chemical or biological sludge, regeneration of biosorbents and possible metal recovery. Due to their humic acid content, vermicomposts are a novel and effective variety of biosorbent for removing metallic ions such as Pb, Ni, Cr, Cd and V from wastewaters. The types of biosorbents surveyed in this chapter are fungal biomass, biomass of nonliving, dried brown marine algae, agricultural wastes and residues, composite chitosan biosorbent prepared by coating chitosan, cellulose based sorbents, and bacterial strains.