Recent advances in the design and use of Pickering emulsions for wastewater treatment applications

Studying surfactant mass transport through dynamic interfacial tension measurements: A review of the models, experiments, and the contribution of microfluidics

Surfactant mass transport towards an interface plays a critical role during formation of emulsions, foams and in industrial processes where two immiscible phases coexist. The understanding of these mechanisms as experimentally observed by dynamic interfacial tension measurements, is crucial. In this review, theoretical models describing both equilibrated systems and surfactant kinetics are covered. Experimental results from the literature are analysed based on the nature of surfactants and the tensiometry methods used. The innovative microfluidic techniques that have become available to study both diffusion and adsorption mechanisms during surfactant mass transport are discussed and compared with classical methods. This review focuses on surfactant transport during formation of droplets or bubbles; stabilisation of dispersed systems is not discussed here.

Carbonized balsa wood-based photothermal evaporator for treating inorganic chemical wastewater

Solar desalination provides a sustainable and eco-friendly solution for purifying wastewater, addressing environmental challenges associated with wastewater treatment. This study focuses on the purification of inorganic contaminants from laboratory chemical wastewater (ICWW) using a spherical solar still (SSS). To enhance the evaporation rate and overcome the impact of heavy metals on absorption efficiency, a carbonized balsa wood (CBW) solar evaporator was employed. Balsa wood pieces, carbonized at 250 °C for 15 min, were arranged in a SSS configuration. The CBW-integrated SSS demonstrated a remarkable freshwater productivity of 2.33 L/m2 for ICWW, surpassing the conventional SSS, which produced only 1.5 L/m2. The presence of heavy metal ions (Na+, Ca+, K+, and Mg2+) in ICWW significantly affected the evaporation rate, and the CBW solar evaporator exhibited an impressive removal efficiency of approximately 99%. Water quality parameters, including pH and chemical oxygen demand (COD), were investigated before and after treatment. The CBW-integrated SSS achieved an outstanding COD removal efficiency of about 99.77%, reducing the COD level from 229.51 to 0.521 mg/L. These results underscore the efficacy of the proposed solar desalination system in purifying ICWW, offering a promising approach to address environmental concerns associated with wastewater treatment.

A review of high internal phase Pickering emulsions: Stabilization, rheology, and 3D printing application

High internal phase Pickering emulsion (HIPPE) is renowned for its exceptionally high-volume fraction of internal phase, leading to flocculated yet deformed emulsion droplets and unique rheological behaviors such as shear-thinning property, viscoelasticity, and thixotropic recovery. Alongside the inherent features of regular emulsion systems, such as large interfacial area and well-mixture of two immiscible liquids, the HIPPEs have been emerging as building blocks to construct three-dimensional (3D) scaffolds with customized structures and programmable functions using an extrusion-based 3D printing technique, making 3D-printed HIPPE-based scaffolds attract widespread interest from various fields such as food science, biotechnology, environmental science, and energy transfer. Herein, the recent advances in preparing suitable HIPPEs as 3D printing inks for various applied fields are reviewed. This work begins with the stabilization mechanism of HIPPEs, followed by introducing the origin of their distinctive rheological behaviors and strategies to adjust the rheological behaviors to prepare more eligible HIPPEs as printing inks. Then, the compatibility between extrusion-based 3D printing and HIPPEs as building blocks was discussed, followed by a summary of the potential applications using 3D-printed HIPPE-based scaffolds. Finally, limitations and future perspectives on preparing HIPPE-based materials using extrusion-based 3D printing were presented.

Preparation and Emulsifying Properties of Carbon-Based Pickering Emulsifier

Water is increasingly being used as a solvent in place of organic solvent in order to meet the demand for green chemical synthesis. Nevertheless, many of the reaction substrates are organic matter, which have low water solubility, resulting in a low reaction interface and limiting the development of organic-water biphasic systems. A surfactant is typically added to the two-phase system to form an emulsion to increase the contact area between the organic phase and the water. Compared to ordinary emulsion stabilized with the surfactant, Pickering emulsion offers better adhesion resistance, biocompatibility, and environmental friendliness. It possesses unrivaled benefits as an emulsifier and catalyst in a two-phase interfacial catalysis system (PIC). In this study, the amine group (NNDB) was employed to alter the surface of graphene oxide (GO). A stable Pickering emulsion was created by adsorbing GO-NNDB on the toluene–water interface. It was determined that the emulsion system had good stability by analyzing digital photographs and microscope images of droplets at various temperatures, and fluorescence microscopy images of emulsion droplets created by both newly added and recovered emulsifiers. This work provided the groundwork for future applications of Pickering emulsion in interfacial catalysis.