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The presence of organic pollutants in the environment is of major concern because of their toxicity, bio-accumulating tendency, threat to human life and the environment. It is a well-known fact that, these pollutants can damage nerves, liver, and bones and could also block functional groups of essential enzymes. Conventional methods for removing dissolved pollutants include chemical precipitation, chemical oxidation or reduction, filtration, ion-exchange, electrochemical treatment, application of membrane technology, evaporation recovery and biological treatment. Although all the pollutant treatment techniques can be employed, they have their inherent advantages and limitations. Among all these methods, adsorption process is considered better than other methods because of convenience, easy operation and simplicity of design. A fundamentally important characteristic of good adsorbents is their high porosity and consequent larger surface area with more specific adsorption sites. This paper presents a review of adsorption of different pollutants using activated carbon prepared from fly ash sources and the attendant environmental implications. Also, the ways of overcoming barriers to fly ash utilization together with regeneration studies are also discussed.

Endocrine-disrupting chemicals (EDCs) are pollutants with adverse effects even at very low concentrations; they remain a major concern for water quality. There is a strong link between environmental matrices such as water, soil, and human health. This implies that releasing these pollutants into the environment gets to the human system through contaminated air, water, and food. EDCs pose adverse effects on the endocrine systems of humans and wildlife and act as agents that interrupt metabolism, transport, synthesis, secretion, or elimination of natural blood-borne hormones present in the human body, which are responsible for the development, reproduction, and homeostasis process. The molecular group known as an endocrine disruptor is extremely heterogeneous, including the usage of synthetic chemicals in industrial solvents, lubricants and their by-products (such as 1,2-dichloroethane, 17α-ethinylestradiol, 17β-estradiol, 2,4-dichlorophenol, acetaminophen, amoxicillin, antiretroviral, benzotriazole, bisphenol A, carbamazepine, ciprofloxacin, diclofenac, ibuprofen, ketoprofen, naproxen, paracetamol, phenol, tetracycline, metformin, etc. discussed in this work). Natural chemicals in food can also act as endocrine disruptors and some of these chemicals are toxic. Contaminants in water influence all living beings; therefore, to prevent health complications, improve water quality and make it safer in the ecosystem, water must be purified. The complex nature of EDCs has necessitated the development of suitable, robust, and more versatile removal techniques capable of producing the desired result in a very cost-effective manner. The first part of this review addresses source and occurrence of EDCs, available EDC treatment technologies and their drawbacks, and followed by the recent advances in sequestrating EDCs using natural, synthetic (metal–organic frameworks, nanoparticle/nanomaterials), and agricultural waste adsorbents. Influence of different operational parameters on the adsorptive removal of EDCs, mechanism of EDCs sequestration and thermodynamic studies were also discussed. We concluded by providing some useful insights, challenges, and future prospects to foster better efficiency of these adsorbents for EDCs removal to meet various industrial applications.

This study investigates the efficacy of acid activated coconut husk (CHA) for the removal of rhodamine-B (Rh-B) dye from aqueous solutions. The CHA prepared was characterized using various techniques: SEM, FTIR EDX, Boehm titration and pHpzc, respectively. The effects of different operational parameters including initial concentration, contact time and solution temperatures were examined. Kinetic data for Rh-B dye adsorption onto CHA fitted best to pseudo-second-order kinetic model considering the correlation regression (R2) and the sum of squares of error values. Adsorption data were fitted to Langmuir, Freundlich, Dubinin–Radushkevich and Temkin isotherm models. Langmuir isotherm was the most fitted among all the models used with maximum monolayer sorption capacity of 1666.67 mg g−1 and the highest regression value of 0.99 indicating that CHA has greater affinity for Rh-B dye adsorption due to increased pore development via acid activation. Thermodynamic studies revealed an endothermic adsorption process with the ΔH0 value of 62.77 kJ mol−1. Spontaneity was ascertained based on the negative values of ΔGo (ranging from − 26.38 kJ mol−1 to − 20.93 kJ mol−1). The positive value of ΔS0 (0.276 kJ mol−1 K−1) suggests increased randomness that exists between CHA and Rh-B dye. Cost analysis results revealed that CHA is six times cheaper than commercial activated carbon (CAC), providing a savings of 217 US$ kg−1. CHA adsorbent was found to be suitable for Rh-B dye removal from aqueous solution.

In direct alcohol fuel cells (DAFCs), energy conversion co‐occurs at the anode (alcohol oxidation reaction [AOR]) and cathode (oxygen reduction reaction [ORR]). The sluggishness of AOR and ORR needs highly electrocatalytically active and stable electrocatalysts that boost electrokinetics, which is central in electrocatalysts’ architectural design and modulation. This design entails enhanced engineering synthesis protocols, heteroatomic doping, metallic doping/alloying, and deliberate introduction of defective motifs within the electrocatalyst matrix. The electrocatalyst activity and behavior depend on the electrocatalysts’ nature, type, composition, and reaction media, acidic or alkaline. Alkaline media permits cheap nonplatinum group metals. This review elucidates the roles and electrocatalytic pathways on different AOR and ORR electrocatalysts and outlines the aspects distinguishing ORR in alkaline and acidic media. It gives up‐to‐date and ultramodern strategies, protocols, and underlying mechanisms pointing to the efficacy and efficiency of electrocatalysts. The focus centers on heteroatomic, metallic dopants, defects effects correlated to electrocatalytic properties and experimental and theoretical findings. For the advancement in the field, the present study discusses critical parameters for improving the performances of electrocatalysts for DAFCs and breakthroughs on the horizon. Conclusively, knowledge gaps and prospects of these materials for industrial viability and reigning futuristic research directions are presented. Electrochemical performance in direct alcohol fuel cells (DAFCs) is influenced by several factors, including deliberately inducing defects (heteroatomic and metallic dopants, defects, dislocations) on electrocatalysts using different engineering methods, and governs electrocatalytic pathways for the oxygen reduction and alcohol oxidation, and the ultimate improvement of DAFCs reactions is fundamental to the industrialization of fuel cell technology.

Carbon nanofibers (CNFs) supported by Pd and Pd-Sn electro-catalysts were prepared by the chemical reduction method using ethylene glycol as the reducing agent. Their physicochemical characteristics were studied using high resolution-transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and Bruanaer-Emmett-Teller (BET) analysis. FTIR revealed that oxygen, hydroxyl, carboxylic and carbonyl functional groups facilitated the dispersion of Pd and Sn nanoparticles. The doping of Pd with Sn to generate PdSn alloy was also confirmed by XPS data. The amorphous nature of CNFs was confirmed by XRD patterns which exhibited the Pd diffraction peaks. When Sn was added to Pd/CNFs, the diffraction peaks moved to lower angles. HRTEM images revealed that the CNFs with cylindrical shape-like morphology and also Pd-Sn nanoparticles dispersed on carbon support. The catalytic activity and stability towards alcohol electro-oxidation in alkaline medium at room temperature was evaluated using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The obtained Pd-Sn/CNFs electro-catalyst exhibited a better electro-catalytic activity than Pd/CNFs and Pd/C electro-catalysts for both methanol and ethanol oxidation. The improvement of the electrochemical performance was associated with the synergistic effect via the addition of Sn which modified the Pd atom arrangement, thereby promoting oxidation through a dehydrogenation pathway. Furthermore, SnO2 generates abundant OH species which helps with increasing the rate of the oxidative removal of carbon monoxide (CO) intermediates from Pd sites.

[...]rapid emergence of carbon dioxide emission and the hazard pose to the environment have led us to the result that it is essential to take proper approaches to stop the building up of CO2 [11-12]. [...]of the complicated nature of the inorganic photocatalyst surface, the interaction between photocatalyst and absorbed species may undergo a series of oneelectron processes instead of a multi-electron, multi-proton process, thus making the actual redox potential required to be dependent on the reaction pathway. [...]the electron transfer efficiency between the dye sensitizer and the semiconductor depends on many factors, which include the LUMO level of the dyes and the conduction band edge of semiconductors [99]. Several other reported works were reviewed on growth over ZnO semiconductor for enhancing photocatalytic performances [173179]. [...]polar inorganic nanocrystal growth is sensitive to solvents reaction, tuning and controlling their morphologies by the crystalsolvent facial interactions [167] is necessary since ZnO morphology is mainly directed by the saturated vapor pressure and polarity of the solvents [170].

A new and novel adsorbent was obtained by impregnation of Moringa oleifera leaf in H 2 SO 4 and NaOH, respectively. Prepared adsorbents were characterized using elemental analysis, FT-IR, SEM, TGA and EDX analyses, respectively. The effects of operational parameters, such as pH, moisture content, ash content, porosity and iodine number on these adsorbents were investigated and compared with those of commercial activated carbon (CAC). EDX results of acid activated M. oleifera leaf have the highest percentage of carbon by weight (69.40 %) and (76.11 %) by atom, respectively. Proximate analysis showed that the fixed carbon content of acid activated M. oleifera leaf (69.14 ± 0.01) was the highest of all adsorbents studied. Conclusively, the present investigation shows that acid activated M. oleifera leaf is a good alternative adsorbent that could be used in lieu of CAC for recovery of dyes and heavy metal from aqueous solutions and other separation techniques.

Adsorption process has proven to be one of the best water treatment technologies around the world and activated carbon is undoubtedly considered as a universal adsorbent for the removal of different types of pollutants from water. However, widespread use of commercial activated carbon is sometimes restricted due to its high cost. Attempts have been made to develop inexpensive adsorbents utilizing numerous agro-industrial and municipal waste materials. Use of agricultural waste materials as low-cost adsorbents is attractive because it reduces the cost of waste disposal, thereby leading to environmental protection. In this review, agricultural, synthetic and other adsorbents used for adsorbing nickel (II) ion from aqueous solutions are reported. Different ways to improve their efficiencies are also discussed.

Groundwater is the major source of drinking water in virtually all the regions of Nigeria, including the southwestern region. It is an indispensable source of drinking water that many individuals are dependent upon for daily activities in Nigeria. However, the spontaneous rise in various forms of industrialization and other anthropogenic activities of man within the southwestern region has immensely polluted these water sources. This calls for tremendous and actionable concern because of the health implications associated with the intake of contaminated water. This study aims to thoroughly disentangle the major impacts of anthropogenic activities on the quality of groundwater in the southwestern region of Nigeria through extensive reviews of literature and conceptualization of scientific and research data on the field. Unlike previous reviews, the major sources of groundwater pollution in the region were discussed extensively to set the tone for the x-raying of the subject. The study also showed major long-standing pollution cases in the region with graphical, tabular, and pictorial illustrations of some of the groundwater parameters and at the same time proposed controlling measures to enable eidetic understanding of the concepts and contribution to knowledge. In the last part of the work, we recommend improving the existing groundwater assessment techniques in Southwestern Nigeria. Regular monitoring of groundwater in Nigeria should also be encouraged to establish its quality status. Graphical abstract

The food insecurity problem in developing countries has been linked to rapid rates of soil loss and decline in fertility in tropical environments which are characterized by insidious topography. This study was conducted to assess the relationship between topographic positions, land use, and soil characteristics. Three slope classes were considered with six pedons; two on each slope position were opened, described, sampled, and analysed for morphological and physicochemical properties. The results showed that the soils were deep to very deep with drainage improving from HK1 soils (very poorly drained) to HK3 (well-drained). The mean sand fraction ranged between 320 and 740 g kg −1 , while bulk density had values between 1.20 and 1.80 M gm −3. The cation exchange capacity (CEC) of the soils with values from 5.6 to 10.4 cmol (+) kg −1 was generally lower on the surface than the subsurface soils. The different landscape positions alongside variation in land use substantially influence variations in soil properties of the study area. The influence of topography was noticed for sand values and soil reaction (pH) along the slope, as mean pH values were significantly ( P  ≤ 0.05) higher for HK1 compared with HK2 and HK3. Intensive cultivation of soils due to rainfed and irrigated land use on middle slope position (HK2) alongside its strong slope gradient resulted in significant variation in total exchangeable bases (TEB) (( P  ≤ 0.05), base saturation ( P  ≤ 0.05), available P (( P  ≤ 0.01), and exchangeable Ca and Mg ( P  ≤ 0.05).