Energy is a requisite factor for technological advancement and the economic development of any society. Currently, global energy demand and supply largely rely on fossil fuels. The use of fossil fuels as a source of energy has caused severe environmental pollution and global warming. To salvage the dire situation, research effort is geared toward the utilization of clean, renewable and sustainable energy sources and the hydrogen energy economy is among the most preferred choices. Hydrogen energy economy, which includes hydrogen production, storage and conversion has gained wide consideration as an ecofriendly future energy solution with a fuel cell as its conversion device. Fuel cells, especially, the proton exchange membrane category, present a promising technology that converts hydrogen directly into electricity with great efficiency and no hazardous emissions. Unfortunately, the current generation of proton exchange membrane fuel cells faces some drawbacks that prevent them from large-scale market adoption. These challenges include the high costs and durability concerns of catalyst materials. The main source of high cost in fuel cells is the platinum catalyst used in the electrodes, particularly at the cathode where the sluggish oxygen reduction reaction kinetics require high loading of precious metals. Many research efforts on proton exchange membrane fuel cells are directed to reduce the device cost by reducing or completely replacing the platinum metal loading using alternative low-cost materials with “platinum-like” catalytic behaviour while maintaining high power performance and durability. Consequently, this review attempts to highlight recent research efforts to replace platinum and carbon support with other cost-effective and durable materials in proton exchange membrane fuel cell electrocatalysts. Overview of promising materials such as alloy-based (binary, ternary, quaternary and high-entropy alloys), single atom and metal-free electrocatalysts were discussed, as the research areas are still in their infancy and have many open questions that need to be answered to gain insight into their intrinsic requirements that will inform the recommendation for outlook in selecting them as electrocatalysts for oxygen reduction reaction in proton exchange membrane fuel cell.

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Materials for electrocatalysts in proton exchange membrane fuel cell: A brief review

Eutrophication is reckoned as an ecological challenge that exhibits adverse effects on the aquatic ecosystem as well as the sustenance of portable water required by humans for their unremitting survival on the earth. There has been a range of techniques for the prevention of eutrophication, consequent on the need for the provision of portable water and the protection of water bodies and the aquatic ecosystem. The employment of chemical coagulants such as lime, magnesium sulphate and ferric sulphate has been reported to yield more than 95% removal of nitrate and phosphate. Moreover, adsorption studies revealed that at optimum pH and a contact time of 60 min, glutaraldehyde cross-linked chitosan exhibited the highest adsorption capacity of 139.4 mg/g, compared to epichlorohydrin cross-linked chitosan and unmodified chitosan that exhibited adsorption capacity of 108.24 and 44.38 mg/g respectively for phosphate removal. The use of nano-filtration membrane coupled with bioreactor (NF-MBR) for 62 days at a flux rate of 16 l/m.h and hydraulic retention time of 2.9 h has been posited to display percentage removal of 95, 90, 89, 87 and 68% for COD, N-NH3, N-NO2, N-NO3- and P-PO43− respectively from wastewater. Lastly, biological techniques such as wetland have been posited to be effective in combating eutrophication by exhibiting percentage removal efficiencies of 86–98% (N-NH4), 99% (N-NO2), 82–99% (N-NO3−), 95–98% (total inorganic nitrogen), 71.2–31.9% (phosphate), 25–55% (COD) and 47–86% (suspended solids). Nevertheless, the success of wetland treatment techniques is slightly impeded by the hydraulic loading rate. 

Eutrophication: Causes, Consequences, Physical, Chemical and Biological Techniques for Mitigation Strategies

Bibliometric evaluation of nanoadsorbents for wastewater treatment and way forward in nanotechnology for clean water sustainability

This study explores adsorptive removal measures to shed light on current water treatment innovations for kinetic/isotherm models and their applications to antibiotic pollutants using a broad range of biomass-based adsorbents. The structure, classifications, sources, distribution, and different techniques for the remediation of antibiotics are discussed. Unlike previous studies, a wide range of adsorbents are covered and adsorption of comprehensive classes of antibiotics onto biomass/biochar-based adsorbents are categorized as β-lactam, fluoroquinolone, sulfonamide, tetracycline, macrolides, chloramphenicol, antiseptic additives, glycosamides, reductase inhibitors, and multiple antibiotic systems. This allows for an assessment of their performance and an understanding of current research breakthroughs in applying various adsorbent materials for antibiotic removal. Distinct from other studies in the field, the theoretical basis of different isotherm and kinetics models and the corresponding experimental insights into their applications to antibiotics are discussed extensively, thereby identifying the associated strengths, limitations, and efficacy of kinetics and isotherms for describing the performances of the adsorbents. In addition, we explore the regeneration of adsorbents and the potential applications of the adsorbents in engineering. Lastly, scholars will be able to grasp the present resources employed and the future necessities for antibiotic wastewater remediation.

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Adsorptive removal of antibiotic pollutants from wastewater using biomass/biochar-based adsorbents

Abstract Modification of the adsorbent surfaces has been considered a fascinating strategy that enhances biomass-based adsorption properties for efficient removal of organic pollutants. This is based on the attempt to replace the cost-ineffectiveness of the commercial activated carbon. The present study discusses different modification strategies and a review on modified biomass materials for the sorption of organic contaminants. Unlike previous literatures in the field, wider range of these pollutants are discussed in this study under different categories including pesticides (such as insecticides, herbicides, fungicides), pharmaceutical (e.g. analgesic and antipyretic drugs, antibiotic drugs, non-steroidal anti-inflammatory drugs and antimalaria drugs), and dyes (e.g. azo, xanthene, miscellaneous diagnostic, tri-aryl methane, and phenol-derived polymeric dyes). It was observed that the acid-activated Posidonia oceanica and HNO 3 -modified rice husk displayed the highest and lowest adsorption capacities of 2681.9 and 0.35 mg/g for removing Rhodamine B dye and methyl parathion pesticide, respectively. The mechanistic aspects of organic pollutants adsorption, their corresponding regeneration studies, and environmental challenges with chemical modifications are also discussed. The use of computational (optimization) models for modified biomass-based adsorbents to remove organic pollutants is devoid in previous reviews but discussed in the present study. To foster more advancement in this field, the concluding part presents various challenges and knowledge gaps for furthering research towards more realistic industrial implementations. 

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Modified biomass adsorbents for removal of organic pollutants: a review of batch and optimization studies

Recent trends in Carbon support for improved performance of Alkaline Fuel cells

The zinc oxide nanoparticle was synthesized via precipitation method. It was characterized using SEM-EDX, FTIR and TEM for morphology, elemental, functional groups and internal structure respectively. The physicochemical behaviour of a refinery effluent was assessed. The untreated raw refinery effluent from the point of discharge contained very high concentrations of pollutants for all the parameters, ranging between, pH (6.52-6.82), Turbidity (10-12 NTU), conductivity (266-289μs/cm), COD (116-138 mg/l), BOD (14-18.5 mg/l), DO (7.5-15.6 mg/l), TDS (436-486 mg/l), TSS (127-133 mg/l), Oil and grease (14.8-16.3 mg/l), sulphate (113-125 mg/l) and chloride (240-280 mg/l). The effluent was treated with ZnO nanoparticle and reduced the pollutants to the normal permissible limit set by WHO, FEPA and NESREA standard for portable water. The treated effluent sample showed values ranging between, pH (6.55-6.6), Turbidity (4.2-4.5 NTU), conductivity (245-246 μs/cm), COD (39-40 mg/l), BOD (10 mg/l), DO (5.6-10.4 mg/l), TDS (151-183 mg/l), TSS (24-28 mg/l), Oil and grease (7.3-9.5 mg/l), sulphate (100 mg/l) and chloride (200 mg/l). The heavy metals profile that was investigated are Fe, Cu, Zn, Pb, Cd and Cr of which were found above the WHO and FEPA permissible limit, however, on the contact with the adsorbent therefore reduced the metals to the permissible limit. It can be ascertain that ZnO nanoparticle can be used as an effective adsorbent for the treatment of petrochemical effluent.

T. Adebusuyi

Papers

Adsorptive removal of antibiotic pollutants from wastewater using biomass/biochar-based adsorbents

Modified biomass adsorbents for removal of organic pollutants: a review of batch and optimization studies

Recent trends in Carbon support for improved performance of Alkaline Fuel cells

Synthesis and Characterization of Zinc Oxide Nanoparticle for the Adsorptive Remediation of Petrochemical Effluents