Electrochemical wastewater and soil treatments are exciting set of technologies that has been well-studied over the recent years as one of the most-effective remediation techniques for the removal of hazardous pollutants from liquids effluents and soil. The main requirement of these technologies is electricity and their sustainability can be largely improved if they are powered by renewable energy sources. Likewise, this green energy powering can help to apply these technologies in remote areas, such as rural communities in developing countries, where no electricity grid is available. This review presents a comprehensive discussion on fundamental concepts and applications of renewable energy driven electrochemical technologies for treating hazardous pollutants in wastewater and contaminated soils. In the first section, the fundamentals of different electrochemical remediation technologies are presented, whereas the next two sections focused on the most applied technologies for powering these electrochemical devices: the solar photovoltaic (PV) (Section 3) and the wind turbines (Section 4). After that, the non-near future is faced with the study of the principles of biomass energy production and how bioelectrochemical systems are starting to be evaluated for powering electrochemical technologies (Section 5). Then, new approaches in the renewable energy driven electrochemical technologies such as triboelectric nanogenerators and photocatalytic fuel cells are described in Section 6. The last section focused on the challenges expected for the near future, describing the most promising storage system and evaluating the scale-up, environmental and economic concerns of the technologies studied in this work.

Renewable energies driven electrochemical wastewater/soil decontamination technologies: A critical review of fundamental concepts and applications

Acid activated clays: Materials in continuous demand

Acid activation is a common chemical modification of clays, usually bentonites, with a hot solution of a mineral acid (typically HCl or H 2 SO 4 ), and it is used for both scientific and industrial purposes. The aim is to obtain partly dissolved material of increased specific surface area, porosity and surface acidity. The product consists partly of the remains of the starting mineral and partly of an amorphous, porous, protonated and hydrated silica phase with a three-dimensional cross-linked framework. Illites containing non-swelling interlayer spaces dissolve more slowly than smectites but the chemical composition of the layers has a greater effect on the process than swellability. The dissolution rate of organoclays decreases with the size of organic cations. Acid activation modifies principal clay properties and thus also their industrial applications. The extent of clay mineral dissolution is derived by many methods, such as chemical analysis, IR or NMR spectroscopy, X-ray diffraction, thermal analysis and microscopic investigation.

Acid Activation of Clay Minerals

The present paper should be considered as a review of the application of Fourier Transform Infra-Red for surface clay characterization. The application of surface clay materials for water treatment, oil adsorption, excipients or as active in drugs has largely increased these recent years. The surface clay material presents hydroxyl groups, which can link very easily water molecules. These hydroxyl groups can react with organic groups and by their vibration in the infra-red region, FT-IR can be easily used as a technical method for surface clay characterization. In this paper, we focus on the determination of Lewis and Bronsted acid sites on the clay surface, a critical review of the sample preparation, the surface characterization of bulk clay and the modified surface clay samples using FT-IR spectroscopy.

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FT-IR Spectroscopy Applied for Surface Clays Characterization *

Biologically-mediated carbon capture and utilization by microalgae towards sustainable CO2 biofixation and biomass valorization – A review

Textural characteristics, surface chemistry and activation of bleaching earth: A review

Recent trends in the development of adsorption technologies for carbon dioxide capture: A brief literature and patent reviews (2014-2018)

Removal of lead by solar-photovoltaic electrocoagulation using novel perforated zinc electrode

Adsorption process technology using solid adsorbents in capturing CO2 is an alternative approach to solve the global greenhouse issue. As such, cost-effective, environmentally friendly and high-performance adsorbents have been developed to this end. This paper describes the preparation of adsorbents derived from palm shell waste with high carbon content, which is then functionalized with deep eutectic solvent (DES) a mixture of choline hydroxide:urea and choline hydroxide:glycerol to enhance the CO2 adsorption capacity. Adsorbents are characterized by their structural, morphological, and chemical properties using XRD, FTIR, SEM, EDX, and BET surface area. The relationship between adsorbent surface characteristics and CO2 adsorption performance was studied. CO2 breakthrough experiments were carried out in a fixed-bed adsorption column at different adsorption temperatures (25–55 °C), feed flow rates (200–600 mL/min), and the initial CO2 concentrations (10–20%). It was found that the amount of CO2 uptake decreased with an increase in adsorption temperature, and feed flow rate. It was observed that DES-based activated carbon with a mixture of choline hydroxide:urea (ACDES 9) exhibited the highest CO2 adsorption capacity (37.2 mg/g) at an adsorption temperature of 25 °C, feed flow rate of 200 mL/min, and CO2 concentrations of 10%. Furthermore, the modified adsorbent still showed good performance even after 11 adsorption-desorption cycles.

Adsorption of CO2 on palm shell based activated carbon modified by deep eutectic solvent: Breakthrough adsorption study

A combination of electrocoagulation with other methods seems to have garnered much attention in the research area for the past decade to eliminate heavy metal ions from the synthetic and real wastewater effluents. Combining two various methods into a single system appears to be an efficient and promising approach for heavy metal removal, mainly due to their cost-effectiveness, simple operation and suitability for industrial applications. Solar photovoltaic systems have gained much attention because they make use of clean, renewable energy and make the treatment method cost-effective. In this regard, it is imperative to explore the potential of solar photovoltaic systems to remove heavy metals. A response surface methodology based on the central composite design (CCD) was employed to examine the effects of three independent variables such as pH, initial Pb(II) concentration and adsorbent dosage. The results indicated that the highest Pb(II) removal efficiency up to 99.88% can be achieved using the CCD model with the following optimum conditions: (1) pH: 6.01, (2) initial Pb(II) concentration: 15.00 mg/L and (3) adsorbent dosage: 2.50 g/L. Based on the results, the combined system offered an attractive alternative over the single electrocoagulation and adsorption treatment systems as it can produce high Pb(II) removal efficiency.

Farihahusnah Hussin

Papers

Textural characteristics, surface chemistry and activation of bleaching earth: A review

Recent trends in the development of adsorption technologies for carbon dioxide capture: A brief literature and patent reviews (2014-2018)

Removal of lead by solar-photovoltaic electrocoagulation using novel perforated zinc electrode

Adsorption of CO2 on palm shell based activated carbon modified by deep eutectic solvent: Breakthrough adsorption study

Combined solar electrocoagulation and adsorption processes for Pb(II) removal from aqueous solution