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Using Fourier transform infrared spectroscopy (FTIR) to identify the sulfate-reducing bacteria (SRB) in Daqing Oilfield sewage. The growth curve of SRB and the adsorption ability of extracellular polymeric substances (EPS) to the Fe2+ were combined to explore iron sulfide generation. X-ray diffraction (XRD) results showed that different species of SRB produce iron sulfides, mainly composed of mackinawite. The growth characteristics of SRB affected the formation of iron sulfides and had a negative charge. Various SRB growth trends were different. The growth of the bacterium in an exponential phase or log phase can be described by the greater concentration of inoculation. And smooth growth trends were contributed to the formation of FeS. At the same time, sulfur-rich, like FeS2, was easily formed when S2− (or S22−) played a major role compared with the protein and polysaccharide functional groups in the negatively charged EPS at the process of Fe2+ adsorption. [ABSTRACT FROM AUTHOR]

In this paper, FeSm/BC composites were prepared using coconut shell biochar (BC) as the carrier. FeSm on FeSm/BC is preferentially oriented along the (001) crystal plane and exhibits a uniform honeycomb morphology. It has a high specific surface area and a small pore size distribution, which is more suitable as a heavy metal ion removal material. The results show that Cr(VI) can be almost completely removed within 120 min under acidic conditions with an initial concentration of 10 mg/L of Cr(VI), a temperature of 20 °C, and a dosage of 0.6 g/L of adsorbent. Where pH was the main factor influencing the removal of Cr(VI):pH affects Cr(VI) removal by changing the form of Cr(VI) in the solution, adsorption free energy, redox potential, charged species on FeSm/BC surface, and the reduction properties of Fe2+ and S2−, low pH value is more favorable for Cr(VI) removal. Coexisting anions in solution inhibit Cr(VI) removal due to competitive adsorption, but coexisting cations have no effect. The adsorption process of Cr(VI) by FeSm/BC follows the pseudo-second-order kinetics and Langmuir adsorption isotherm model, indicating that the adsorption process is a monolayer surface adsorption controlled by the chemical adsorption mechanism and involves electron sharing or exchange between adsorbent and adsorbate. Thermodynamic study shows that the adsorption process is a spontaneous entropy-increasing process, and raise the temperature is beneficial to the adsorption. The removal of Cr(VI) by FeSm/BC is the synergistic effect of adsorption, reduction, and co-precipitation. [ABSTRACT FROM AUTHOR]

Composite additives for enhancing the yield stress, sedimentation stability, and long‐term reversibility of bidisperse magnetorheological fluids (MRFs) are reported herein. The design and introduction of magnetic Fe3O4/halloysite‐nanotube (HNT) composite additives to carbonyl‐iron (CI)‐based MRFs are described, and the effects of Fe3O4/HNT addition on the MRF behavior are elucidated. The rheological, viscoelastic, and cyclic reversibility analyses of the bidisperse Fe3O4/HNT‐CI MRFs indicate that the MR performance increases and subsequently decreases with the increasing content of the Fe3O4/HNTs. The MRF containing 1.0 wt% Fe3O4/HNTs shows optimal MR properties and long‐term reversibility. Under a magnetic field, the 1.0 wt% Fe3O4/HNTs are embedded in the interstices of the magnetic chains, enhancing the magnetic dipole–dipole interactions between the particles, strengthening the rigidity of the magnetic chains, and increasing the yield stress of the MRF. The Fe3O4/HNTs are adsorbed on the surfaces of the CI particles in the absence of a magnetic field, occupying the free space between the CI particles and forming support structures, which prevents aggregation and improves sedimentation stability. Moreover, the designed MRFs respond quickly to magnetic field switching and exhibit enhanced long‐term reversibility. [ABSTRACT FROM AUTHOR]

The interfacial properties of sodium para-dimethyl alkylbenzene sulfonate surfactant p-S14-41 (formula is C 22 H 37 SO 3 N a) at the oil-water interface in the presence of monovalent metal counterions (Li+, Na+, K+ and Cs+) are investigated by the spinning drop tensiometry. In the presence of monovalent metal counterions (Na+, K+ and Cs+), the interfacial tension (IFT) of oil-water first decreases and then increases with the increase of counterion concentration, while for Li+ concentration in the studied concentration range, the IFT decreases continuously. The reason why the latter (Li+) does not appear the optimum salinity is that the salt concentration is not high enough. The most noteworthy feature is that not only the different counterions affect differently the optimum salinity but also the concentration of p-S14-4 in the studied concentration range for the same counterion has no effect on the optimum salinity. Besides, the optimum salinity is affected by the electrostatic interaction, water-oil ratio (WOR), salting-out effect, and the hydrated radius of counterion, under the synergistic effect of which, the optimum salinity value order under various monovalent metal counterions is as follows: Li+ > Na+ > Cs+ > K+. The influence mechanism of counterions on the adsorption of p-S14-4 at the oil-water interface is also discussed in detail. [ABSTRACT FROM AUTHOR]