A sustainable strategy for remediation of oily sewage: Clean and safe

An Eco-Friendly Manner to Prepare Superwetting Melamine Sponges with Switchable Wettability for the Separation of Oil/Water Mixtures and Emulsions

Oil/water separation processes have garnered significant global attention due to the quick growth in industrial development, recurring chemical leakages, and oil spills. Hence, there is a significant demand for the development of inexpensive superwetting materials in an eco-friendly manner to separate oil/water mixtures and emulsions. In this study, a superwetting melamine sponge (SMS) with switchable wettabilities was prepared by modifying melamine sponge (MS) with sodium dodecanoate. The as-prepared SMS exhibited superhydrophobicity, superoleophilicity, underwater superoleophobicity, and underoil superhydrophobicity. The SMS can be utilized in treating both light and heavy oil/water mixtures through the prewetting process. It demonstrated fast permeation fluxes (reaching 108,600 L m-2 h-1 for a light oil/water mixture and 147,700 L m-2 h-1 for a heavy oil/water mixture) and exhibited good separation efficiency (exceeding 99.56%). The compressed SMS was employed in separating surfactant-stabilized water-in-oil emulsions (SWOEs), as well as surfactant-stabilized oil-in-water emulsions (SOWEs), giving high permeation fluxes (reaching 7210 and 5054 L m-2 h-1, respectively). The oil purity for SWOEs' filtrates surpassed 99.98 wt% and the separation efficiencies of SOWEs exceeded 98.84%. Owing to their remarkable capability for separating oil/water mixtures and emulsions, eco-friendly fabrication method, and feasibility for large-scale production, our SMS has a promising potential for practical applications.

Preparation of Cationic Polyacrylamide Suspension and Its Application in Oilfield Wastewater Treatment

Cationic polyacrylamide (CPAM) solid particle is one of the most commonly used organic polymer flocculants in oilfield wastewater treatment, but it poses some problems, such as a slow dissolution rate and an easy formation into a "fish-eye" in the process of diluting into aqueous solution. However, the current liquid CPAM products also have some problems, such as low effective content, poor storage stability, degradation in a short time, and high preparation costs. In this paper, a CPAM suspension was successfully prepared with 50.00% CPAM fine powder, 46.87% oil phase solvent, 0.63% separating agent, 1.56% emulsifying and dispersing agent, and 0.94% rheology modifier. This suspension has an effective content of 50.00%. It also showed no separation in 7 days of storage at room temperature, no separation in 30 min of centrifugation at a speed of 2000 rpm, and diluted to a 0.40% solution in just 16.00 min. For 1000 NTU of diatomite-simulated wastewater, the optimal turbidity removal rate of the suspension was 99.50%, which was higher than the optimal turbidity removal rate of 98.40% for the inorganic flocculant polymeric aluminum chloride (PAC). For oilfield wastewater, the optimal turbidity removal rate of the CPAM suspension was 35.60%, which was higher than the optimal turbidity removal rate of 28.40% for solid particle CPAM. In a scale-up test, the CPAM suspension achieved a good application effect.

Durable underwater super-oleophobic/super-hydrophilic conductive polymer membrane for oil-water separation

Oily sewage has made serious impact on environment and people's life, and its treatment has become a global problem to be urgently solved. Oil-water separation has been considered to be an effective method to treat oily sewage at present. In this work, an underwater super-oleophobic/super-hydrophilic membrane with oil-water separation and self-cleaning properties was fabricated by electrochemical oxidation of sodium lignosulfonate doped polypyrrole. The membrane showed super-hydrophilicity for water-removal in air and super-hydrophilicity for oil-removal underwater in both oxidation and reduction states. The oil-water separation efficiency of the membranes for different organics exceeded 98.44%, no matter in oxidation or reduction state. Moreover, the membrane still exhibited excellent performance in terms of the oil-water separation efficiency and flux after 70 cycles, which were greater than 97.18% and 70.14 L·m-2·h-1, respectively. Simultaneously, through exploration of the mechanism, it was found that the larger anion kept intact in the membrane during the redox process, which made the stability of composition and performance. Thus, the membrane with advantageous properties, including underwater super-oleophobic/super-hydrophilicity, high oil-water separation efficiency, high circulating rate and stability, has significant potential in separation and collection of oily sewage.

Constructing a highly tough, durable, and renewable flexible filter by epitaxial growth of a glass fiber fabric for high flux and superefficient oil-water separation

The separation and purification of complex and stable stubborn oily sewage is extremely challenging. To respond to this challenge, we developed a powerful flexible filter with ultrahigh strength, durability, flux, separation efficiency, and a multiobjective separation function based on a universal epitaxial growth process of glass fiber fabric (Gf). The underwater oil contact angle (UOCA) of the silicate@Gf (MgSi@Gf) filter is 156.3°, so it can achieve both an ultrahigh permeation flux (5632.7 L·m^-2·h^-1) and oil-water separation efficiency (99.5%) under gravity (≈ 1 kPa) in purifying surfactant-stabilized emulsions, actual industrial oily sewage and mechanical cold rolling emulsions. The filter with a high tensile strength (66.5 MPa) and oil invasion pressure (4626 Pa) can withstand the impact of much sewage or intense water flow. The filter can tolerate extreme conditions and can maintain high separation performance in acid or alkaline (pH 1-13), high or low temperature (100 °C, 200 °C, -18 °C) conditions or natural salty waters such as seawater. The filter can remove methylene blue (MB) dye (99.8%) by filtration, and can be repeatedly and easily reconstructed (renewable advantage). The filter shows great potential for efficiently eliminating the hazards of contaminants in actual oily sewage and thus protect human health.

Nanomaterials for Remediation of Environmental Pollutants

Today, environmental contamination is a big concern for both developing and developed countries. The primary sources of contamination of land, water, and air are extensive industrialization and intense agricultural activities. Various traditional methods are available for the treatment of different pollutants in the environment, but all have some limitations. Due to this, an alternative method is required which is effective and less toxic and provides better outcomes. Nanomaterials have attracted a lot of interest in terms of environmental remediation. Because of their huge surface area and related high reactivity, nanomaterials perform better in environmental clean-up than other conventional approaches. They can be modified for specific uses to provide novel features. Due to the large surface-area-to-volume ratio and the presence of a larger number of reactive sites, nanoscale materials can be extremely reactive. These characteristics allow for higher interaction with contaminants, leading to a quick reduction of contaminant concentration. In the present review, an overview of different nanomaterials that are potential in the remediation of environmental pollutants has been discussed.

Reduction of 4-nitrophenol using green-fabricated metal nanoparticles

Noble metal (silver (Ag), gold (Au), platinum (Pt), and palladium (Pd)) nanoparticles have gained increasing attention due to their importance in several research fields such as environmental and medical research. This review focuses on the basic perceptions of the green synthesis of metal nanoparticles and their supported-catalyst-based reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The mechanisms for the formation of these nanoparticles and the catalytic reduction of 4-NP are discussed. Furthermore, the parameters that need to be considered in the catalytic efficiency calculations and perspectives for future studies are also discussed.

Noble metal (silver (Ag), gold (Au), platinum (Pt), and palladium (Pd)) nanoparticles have gained increasing attention due to their importance in several research fields such as environmental and medical research.

Advanced super-hydrophobic polymer-based porous absorbents for the treatment of oil-polluted water

The threat of environmental pollution caused by spilled oil is rapidly increasing along with the expansion of oil exploration, the development of maritime activities and industrial growth. Oil spill incidents usually affect seriously the ecosystem and human life. Therefore, the treatment and recovery of the oil spill have been considered as an ultra-important issue to protect the environment and to minimize its negative impacts on socio-economic activities. Among methods of oil spill recovery, porous materials have emerged as potential absorbents possessing the capacity of absorbing spilled oil at a fast rate, high adsorption capacity, good selectivity, and high reusability. In this review paper, two types of polymer-based porous absorbents modified surface and structure were introduced for the treatment strategy of the oil-polluted water. In addition, the absorption mechanism and factors affecting the adsorption capacity for oils and organic solvents were thoroughly analyzed. More importantly, characteristics of polymer-based porous materials were discussed in detail based on microstructure analysis, absorption efficiency, and reusability. In general, this paper has provided an overview and a comprehensive assessment of the use of advanced polymer-based porous materials for the treatment of oil-polluted water, although the impacts of environmental factors such as wind, wave, and temperature should be further investigated in the future.