The role of mixing in high performance Adsorptive Micellar Flocculation

Enhanced oil droplet aggregation and demulsification by increasing electric field in electrocoagulation

Electrocoagulation (EC) is an efficient technology for removing oil-in-water (O/W) emulsions. However, the role of the electric field in EC for demulsification remains unclear and an obstacle for improving reactor design and operation. Herein, demulsification and oil removal performance by EC under different electric field conditions were investigated. Increasing the EC electric field intensity was beneficial for oil removal, and tandem EC had a higher electric field intensity than parallel EC under the same current density. When the current density was 0.67 mA cm^-2, the chemical oxygen demand (COD) removal rates of tandem EC and parallel EC were 1 136.47 and 745.99 g COD kWh^-1, respectively. Oil droplets were polarized by the electric field, and then aligned and aggregated parallel to the direction of the electric field. Increasing electric field intensity accelerated the aggregation of oil droplets, as verified by physical fluid simulation. Furthermore, results showed a higher Al³⁺ dosage and larger electric field intensity in EC with increasing current density, which was conducive to oil droplet demulsification. These findings provide insight into and a theoretical basis for improving oil removal by EC processes.

Advances in micro interfacial phenomena of adsorptive micellar flocculation: Principles and application for water treatment

Among various aqua remediation technologies, separation aims at cleaning pollutants by isolating them despite their destruction; solutes can also be recovered after the process. Adsorptive micellar flocculation (AMF) has been known as an important surfactant-based technique to separate poorly water-soluble hazardous pollutants from aqua media as an efficient and energy-intensive replacement for other surfactant-based techniques, as such AMF should be known. AMF is based on the partitioning of solutes gradient from bulk solution into the nanosized smart anionic surfactant micelle followed by flocculation. However, unlike coagulation/flocculation or adsorption, AMF is not viable for the production of drinking water in water utilities due to the loss of surfactant monomers. Unfortunately, it can be used as a reservoir or for the recycling/recovery of organic pollutants (intermediates) (ions, organics/bioactive, dyes, etc.), even at high concentrations. The performance of AMF depends on various parameters, and this review briefly summarizes the existing researches on different pollutants removal by AMF and material recovery/recycling. This includes operating condition factors (surfactants, flocculants, surfactant-flocculant or surfactant-pollutant concentration ratio, and water conditions chemistry). Because varieties of micro interfacial phenomena other than physical interactions occur in a versatile micellar environment in the AMF process, emphases are given to adsorptive oxidation, micellar catalysis, selectivity. Furthermore, for the first time, this review gives an overview of understanding the state-of-the-art multifunctional nano amphiphile-based AMF that behaves mimetic to aquatic organisms in the process of pollutant removal. The efficiency of AMF, including recycling concentrated solution without noticeable deterioration, as an auxiliary resource/income for the next cycle, signifies economic viability, versatility, and manifold applications in aqua remediation. Significance, ways to achieve enhanced process efficiency, as well as challenges and future opportunities in wastewater treatment, are also highlighted.

Preparation and flocculation properties of modified alginate amphiphilic polymeric nano-flocculants

The novel nano-flocculants were synthesized through a conjugation of dodecylamine with partly oxidized sodium alginate. The structures of the flocculants were characterized by FTIR, ¹HNMR, TGA, and EA. The flocculants possessed amphiphilic structures and formed nano-micelles through self-assembly in water. The nano-micelles showed rod-like shapes about 100 nm. Removal rates of the flocculants for Pb²⁺ and bisphenol A were determined under different conditions, showing the removal rates as high as 97.20% and 88.66% for Pb²⁺ and bisphenol A, respectively. The flocculation mechanisms were revealed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM), respectively. Isotherm adsorption studies indicated that the flocculation for Pb²⁺ accorded with the Langmuir single-layer adsorption model, and for bisphenol A accorded with the Freundlich multi-layer adsorption model. The quasi-second-order kinetic model was suitable for describing the adsorption kinetics. The new nano-flocculant was a promising agent for removing both heavy metal ions and organic pollutants of wastewater.