Flexible nanoporous activated carbon for adsorption of organics from industrial effluents.

This paper reports a study involving the formation of a self-assembled polymeric monolayer on the surface of a high surface area activated carbon to engineer its affinity towards organic contaminants. A nanoporous activated carbon cloth with a surface area of ∼1220 m2 g-1 and a pore volume of ∼0.42 cm3 g-1 was produced by chemical impregnation, carbonisation and high-temperature CO2 activation of a commercially available viscose rayon cloth. The subsequent modification with a silane polymer resulted in a nanoscale self-assembled monolayer that made it selective towards organic solvents (contact angle <10°) and repellant towards water (contact angle >145°). The adsorbent showed more than 95% efficiency in the separation of various types of oil/water mixtures under neutral, basic and acidic conditions. Benefiting from inherent nanoscale features, a robust hierarchical structure and a thermally stable monolayer (∼300 °C), this nanoporous adsorbent maintained high efficiency for more than 20 cycles and separated surfactant stabilised emulsion with >92% oil removal efficiency. The adsorbent was studied extensively with a series of advanced characterisation techniques to establish the formation mechanism and performance in emulsion separation. Findings from this work provide crucial insights towards large-scale implementation of surface engineered activated carbon-based materials for a wide range of industrial separation applications.

Surface Engineering of Ceramic Nanomaterials for Separation of Oil/Water Mixtures.

Oil/water mixtures are a potentially major source of environmental pollution if efficient separation technology is not employed during processing. A large volume of oil/water mixtures is produced via many manufacturing operations in food, petrochemical, mining, and metal industries and can be exposed to water sources on a regular basis. To date, several techniques are used in practice to deal with industrial oil/water mixtures and oil spills such as in situ burning of oil, bioremediation, and solidifiers, which change the physical shape of oil as a result of chemical interaction. Physical separation of oil/water mixtures is in industrial practice; however, the existing technologies to do so often require either dissipation of large amounts of energy (such as in cyclones and hydrocyclones) or large residence times or inventories of fluids (such as in decanters). Recently, materials with selective wettability have gained attention for application in separation of oil/water mixtures and surfactant stabilized emulsions. For example, a superhydrophobic material is selectively wettable toward oil while having a poor affinity for the aqueous phase; therefore, a superhydrophobic porous material can easily adsorb the oil while completely rejecting the water from an oil/water mixture, thus physically separating the two components. The ease of separation, low cost, and low-energy requirements are some of the other advantages offered by these materials over existing practices of oil/water separation. The present review aims to focus on the surface engineering aspects to achieve selectively wettability in materials and its their relationship with the separation of oil/water mixtures with particular focus on emulsions, on factors contributing to their stability, and on how wettability can be helpful in their separation. Finally, the challenges in application of superwettable materials will be highlighted, and potential solutions to improve the application of these materials will be put forward.

Scalable and Universal Route for the Deposition of Binary, Ternary, and Quaternary Metal Sulfide Materials from Molecular Precursors.

A range of binary, ternary (CFS), and quaternary (CZTS) metal sulfide materials have been successfully deposited onto the glass substrates by air-spray deposition of metal diethyldithiocarbamate molecular precursors followed by pyrolysis (18 examples). The as-deposited materials were characterized by powder X-ray diffraction (p-XRD), Raman spectroscopy, secondary electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy, which in all cases showed that the materials were polycrystalline with the expected elemental stoichiometry. In the case of the higher sulfides, EDX spectroscopy mapping demonstrated the spatial homogeneity of the elemental distributions at the microscale. By using this simple and inexpensive method, we could potentially fabricate thin films of any given main group or transition metal chalcogenide material over large areas, theoretically on substrates with complex topologies.