Research on the coagulant aid effects of modified diatomite on coal microbial flocculation

Adsorption Properties of Diatomite Minerals on Glyceryl Monostearate for Antifogging of the Plastic Film

Adding an appropriate amount and the stable precipitation of surfactant on the inner surface of agricultural plastic greenhouse films can prevent the formation of water droplets on the inner surface of the film to reduce its harmful effects in the process of plant cultivation and production. In this work, for the stable precipitation of the surfactant glycerol monostearate, diatomite minerals from three origins in China were compared through structural analysis and adsorption performance. The effects of acid treatments and alkali treatments on the mineral structure were studied, and the adsorption mechanism of glycerol monostearate was further investigated. The results show that the structural characteristics of Jilin diatomite are more suitable as adsorbents for glyceryl monostearate adsorption. Because diatomite is resistant to acids but not alkalis, when diatomite is treated with an alkali, impurities on its surface can be removed and the hydroxyl group and specific surface area can be greatly increased. The adsorption capacity of glycerol stearate was increased to 218.4 mg/g, or 32.08%, over its pretreatment level. The results show that this is mainly the result of physical adsorption caused by van der Waals force imbalance and chemisorption caused by a small number of hydrogen bonds. In addition, the dripping performance of this composite dripping film with mineral diatomite was better than that of the commercial dripping film, which provided a theoretical basis for efficient mineral slow-release drip irrigation composite film.

Preparation, characterization and application of a composite bioflocculant

Composite flocculant PAFS-PDM was prepared from Polymeric aluminium ferric sulphate (PAFS) and Poly (diallyl dimethyl ammonium chloride) (PDM) in this study. A bacterium was selected from the soil near the shale gas exploitation platform as a bioflocculant-producing bacterium, and polysaccharide was extracted and combined with PAFS-PDM to obtain composite bioflocculant (CBF) to treat shale gas fracturing flowback fluid. The prepared CBF was characterized and the results showed that the prepared PAFS-PDM contained aluminium-iron hydroxyl polymer, which was a cationic flocculant. By measuring the turbidity removal rate and chemical oxygen demand (COD) removal efficiency, the function mechanism of CBF on the shale gas fracturing flowback fluid was discussed. The results showed that CBF had a stable treatment effect on fracturing flowback fluid when the pH value was about 7.0. With the increase of dosage, the coagulation efficiency increased first and then decreased. When the dosage of the CBF was 2500 mg·L-1, the treatment effect of shale gas fracturing flowback fluid was the best, and COD removal rate reached 89.43%. Through Zeta potential analysis, it was concluded that one of the coagulation mechanisms was electrical neutralization. According to the characterization results, it could be concluded that both adsorption bridging and charge neutralization mechanisms played important roles in the treatment of shale gas fracturing flowback fluids.

Settleability and dewaterability of sewage sludge with modified diatomite

In this study, cationic polyacrylamide (CPAM)-modified diatomite and cetyl trimethyl ammonium bromide (CTAB)-modified diatomite were synthesized and used as conditioners for sewage sludge dewatering. The effects of these two types of modified diatomite on the dewaterability and settling performance of the activated sludge were studied. The mechanisms of the two modified diatomite types in the activated sludge system were elucidated. The efficiency of the CPAM-modified diatomite was better than that of the CTAB-modified diatomite in improving the settleability and dewaterability of sludge. The results indicated that specific resistance to filtration (SRF) was decreased from 8.52 × 10¹² to 0.92 × 10¹² m/Kg, and the water content in the remaining sludge cake after pumping filtration was decreased from 92.2 to 68.1% by adding 0.4% of CPAM-modified diatomite and pH = 3.5, which resulted in excellent sludge settling of activated sludge. Further studies showed that the polymer/surfactant adsorbed in diatomite increased sludge dewaterability and improved the sedimentation rate owing to stripping extracellular polymeric substances (EPS) and damaging the internal structure of the sludge, leading to sludge conduce bound water release. According to scanning electron microscope (SEM) images, the two types of modified diatomite powder maintained the porous structure and showed a more complete and uniform structure compared to natural diatomite.