BS12-assisted flotation for the intensification of SNPs separation from CMP wastewater using a novel flotation column

Recovery of Fluoride-Rich and Silica-Rich Wastewaters as Valuable Resources: A Resource Capture Ultrafiltration-Bipolar Membrane Electrodialysis-Based Closed-Loop Process

Traditional technologies such as precipitation and coagulation have been adopted for fluoride-rich and silica-rich wastewater treatment, respectively, but waste solid generation and low wastewater processing efficiency are still the looming concern. Efficient resource recovery technologies for different wastewater treatments are scarce for environment and industry sustainability. Herein, a resource capture ultrafiltration-bipolar membrane electrodialysis (RCUF-BMED) system was designed into a closed-loop process for simultaneous capture and recovery of fluoride and silica as sodium silicofluoride (Na₂SiF₆) from mixed fluoride-rich and silica-rich wastewaters, as well as achieving zero liquid discharge. This RCUF-BMED system comprised two key parts: (1) capture of fluoride and silica from two wastewaters using acid, and recovery of the Na₂SiF₆ using base by UF and (2) UF permeate conversion for acid/base and freshwater generation by BMED. With the optimized RCUF-BMED system, fluoride and silica can be selectively captured from wastewater with removal efficiencies higher than 99%. The Na₂SiF₆ recovery was around 72% with a high purity of 99.1%. The aging and cyclic experiments demonstrated the high stability and recyclability of the RCUF-BMED system. This RCUF-BMED system has successfully achieved the conversion of toxic fluoride and silica into valuable Na₂SiF₆ from mixed wastewaters, which shows great application potential in the industry-resource-environment nexus.

Application of surfactants in papermaking industry and future development trend of green surfactants

In this work, the application of chemical surfactants, including cooking aids, detergents, surface sizing agents, and deinking agents as core components, is introduced in the wet end of pulping and papermaking. This method for the combined application of enzymes and surfactants has expanded, promoting technological updates and improving the effect of surfactants in practical applications. Finally, the potential substitution of green surfactants for chemical surfactants is discussed. The source, classification, and natural functions of green surfactants are introduced, including plant extracts, biobased surfactants, fermentation products, and woody biomass. These green surfactants have advantages over their chemically synthesized counterparts, such as their low toxicity and biodegradability. This article reviews the latest developments in the application of surfactants in different paper industry processes and extends the methods of use. Additionally, the application potential of green surfactants in the field of papermaking is discussed. KEY POINTS: • Surfactants as important chemical additives in papermaking process are reviewed. • Deinking technologies by combined of surfactants and enzymes are reviewed. • Applications of green surfactant in papermaking industry are prospected.

The effect of cationic surfactants on improving natural clinoptilolite for the flotation of cesium

Flotation using cationic surfactants has been investigated as a rapid separation technique to dewater clinoptilolite ion exchange resins, for the decontamination of radioactive cesium ions (Cs⁺) from nuclear waste effluent. Initial kinetic and equilibrium adsorption studies of cesium, suggested the large surface area to volume ratio of the fine zeolite contributed to fast adsorption kinetics and high capacities (q_c = 158.3 mg/g). Adsorption of ethylhexadecyldimethylammonium bromide (EHDa-Br) and cetylpyridinium chloride (CPC) surfactant collectors onto both clean and 5 ppm Cs⁺ contaminated clinoptilolite was then measured, where distribution coefficients (K_d) as high as 10,000 mL/g were evident with moderate concentrations CPC. Measurements of particle sizes confirmed that adsorption of surfactant monolayers did not lead to significant aggregation of the clinoptilolite, while < 8% of the 5 ppm contaminated cesium was remobilised. Importantly for flotation, both the recovery efficiency and dewatering ratios were measured across various surfactant concentrations. Optimum conditions were found with 0.5 mM of CPC and addition of 30 μL of MIBC frother, giving a recovery of ∼90% and a water reduction ratio > 4, highlighting the great viability of flotation to separate and concentrate the contaminated powder in the froth phase.

The Performance and Adsorption Mechanism of a Novel Collector, Dodecyl Dimethyl Betaine (BS-12), for the Flotation Separation of Ilmenite and Titanaugite

In this paper, a novel collector, dodecyl dimethyl betaine (BS-12), was used in the selective separation of ilmenite from titanaugite. The flotation performance and associated adsorption mechanism were studied by micro-flotation experiments, particle size analysis, Fourier-transform infrared (FT-IR) spectroscopy analysis, and X-ray photoelectron spectroscopy (XPS) analysis. The micro-flotation results indicated that BS-12 exhibited a stronger collecting ability towards ilmenite than titanaugite within an acidic pH range, and that the recovery of ilmenite was about 50% higher than that of titanaugite under the optimum flotation conditions. Particle size analysis demonstrated that BS-12 could selectively agglomerate ilmenite to a certain extent and then contribute to the flotation difference between ilmenite and titanaugite. FT-IR results showed some characteristic bands of BS-12 on treated ilmenite, and on titanaugite with BS-12. The XPS analysis further confirmed that BS-12 chemisorbed onto ilmenite and titanaugite in a similar way, but the limited active sites on titanaugite in comparison with ilmenite accounted for their differences in flotation.

In-situ activated nanoparticle as an efficient and recyclable foam stabilizer for enhancing foam separation of LAS

Linear alkylbenzene sulfonate (LAS) is a particular member of the emerging contaminants, because of its increasingly ubiquitous use and tremendous harm to the environment and wastewater treatment plant. Herein, we develop a novel two-stage foam separation to recover LAS (18.7-91.0 mg/L) from laundry wastewater. We first reported the fabrication of activated silica nanoparticle (SNP) via a facile and scalable in-situ approach. To obtain a desirable surface property, the key design element was the utilization of amphoteric surfactant, viz. cocamidopropyl betaine, as the modifier. In the first-stage, activated SNP could serve as an efficient foam stabilizer to improve the foam stability and the interfacial adsorption of LAS. Remarkably, LAS concentration in effluent decreased to very low levels of 1.9-2.9 mg/L with a proper enrichment ratio, and met the emission standard. In the second-stage, we originally adopted the intensification of liquid drainage to selectively recycle activated SNP from LAS. An inclined foam channel (IFC) covered by hydrophobic coating was constructed and the maximum recovery percentage of SNP reached 91.5%, indicating that the activated SNP was recyclable. This work definitely proves that the integration of nanotechnology in foam separation can make wastewater treatment more efficient and less expensive.

Polyaluminum chloride-functionalized colloidal gas aphrons for flotation separation of nanoparticles from water

The present work used the coagulative colloidal gas aphron (CCGA)-involved flotation as a robust technology to efficiently remove the typical engineered nanoparticles - silica nanoparticles (SNPs) from water. The inorganic polymer coagulant - polyaluminum chloride (PACl) was used to surface-functionalize the zwitterionic surfactant (C15B)-based CGAs. Results denote that the physicochemical conditions of PACl/C15B mixed solution markedly influenced the flotation behaviors by changing the properties of CCGAs. The C15B molecules showed different dissociated states and interaction behaviors with Al species with the variation of pH. The addition of salt into the PACl/C15B mixed solution decreased the foamability of solution, and the bubbles collapsed before they could efficiently capture SNPs in their rising trajectory. The optimum SNP removal (87.2%) was obtained when the pH and the additional ionic strength of PACl/C15B mixed solution were ∼4.7 and ≤ 1.0 g NaCl/L, individually, and the pH of SNP suspension was ∼9.4. Importantly, modifying PACl on microbubbles took greater advantages than directly using it as coagulant in terms of SNP removal and PACl utlization. The CCGAs were robust since their colloidal attraction and collision efficiency with SNPs were simultaneously enhanced. The PACl was more efficiently utilized during flotation whilst the regular chemical-dosing unit was omitted.