High air flotation efficiency of multiphase flow pump with the addition of dodecyl dimethyl benzyl ammonium chloride (DDBAC)

Recently, centrifugal multiphase pump–dissolved air flotation (CMP-DAF) has become an increasingly popular alternative to DAF that can achieve more stable performance and higher removal efficiency, and this method is widely used in sewage treatment. However, the nonuniformity of the bubble size and low adherence of the floc particles and bubbles, as well as the complicated raw water quality, pose great challenges to CMP-DAF, which does not meet the standards of water supply and drainage in practical use. In the present study, the surfactant dodecyl dimethyl benzyl ammonium chloride (DDBAC) was utilized as a flotation agent to further improve the flotation efficiency of the CMP-DAF process. DDBAC at a dosage of 0.2 mg/L was introduced to the air flotation of raw water to construct a flotation enhanced CMP air flotation system. The results showed that the average turbidity decreased to 0.433 ± 0.017 NTU, and effluent floc particles were present at 1,053 cnt/mL with an acceptable removal rate of 96.20%. In addition, 34.0% and 30.1% of UV254 and CODMn were removed, respectively. These results imply that DDBAC can increase the collision efficiency of bubble particles by reducing the diameter of the bubbles, which is conducive to forming larger flocs, and enhancing the shear resistance of the bubble–floc particles, thus improving the air flotation efficiency.

Optimized anti-biofouling performance of bactericides/cellulose nanocrystals composites modified PVDF ultrafiltration membrane for micro-polluted source water purification

The covalently functionalized cellulose nanocrystal (CNC) composites were synthesized by bonding common bactericides, such as dodecyl dimethyl benzyl ammonium chloride (DDBAC), ZnO and graphene oxide (GO) nanosheets, onto the CNC's surface. Then, the DDBAC/CNC, ZnO/CNC and GO/CNC nanocomposites modified polyvinylidene fluoride (PVDF) ultrafiltration membranes were fabricated by a simple one-step non-solvent induced phase separation (NIPS) process. The resultant hybrid membranes possessed porous and rough surfaces with more finger-like macropores that even extended through the entire cross-section. The hydrophilicity, permeability, antibacterial and antifouling performance and mechanism of the hybrid ultrafiltration membranes were evaluated and compared in detail, aiming at screening a superior hybrid membrane for practical application in micro-polluted source water purification. Among these newly-developed hybrid membranes, GO/CNC/PVDF exhibited an enhanced perm-selectivity with a water flux of 230 L/(m2 h bar) and humic acid rejection of 92%, the improved antibacterial activity (bacteriostasis rate of 93%) and antifouling performance (flux recovery rate (FRR) of >90%) being due to the optimized pore structure, higher surface roughness, incremental hydrophilicity and electronegativity. A lower biofouling level after three weeks' filtration of the actual micro-polluted source water further demonstrated that embedding the hydrophilic and antibacterial GO/CNC nanocomposite into the polymer matrix is an effective strategy to improve membrane anti-biofouling ability.

Preparation of Modified Montmorillonite—Plant Fiber Composite Foam Materials

In the present study, plant fiber foam materials have significant differences in density compared to conventional plastic foam materials. In view of the current problems of fiber foam materials, the montmorillonite (MMT) organically modified by octadecyl-dimethyl-benzyl-ammonium chloride (ODBA) was added to the preparation of composite foam materials by optimizing the existing formula. The properties of organic montmorillonite (OMMT) and the prepared composite foam materials were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), and a standing wave tube sound absorption tester. The results showed that the pore size inside the plant fiber foam materials with the addition of OMMT was more uniform and arranged more closely and orderly. In addition, when the OMMT was added to 0.1 g, the density of the prepared OMMT-bagasse composite foam materials reached its lowest point of 0.079 g/cm3, which was shared with high foam materials.