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A large number of stable oil-in-water (O/W) emulsions are generated by the petroleum industry each year, resulting in a series of operational and environmental challenges. In this study, a RH-NH2 demulsifier was prepared for the separation of O/W emulsions by grafting ethylenediamine onto natural rice husk. RH-NH2 was characterized using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). When the dosage of RH-NH2 was 50 mg/L, the light transmittance (WT) and corresponding oil removal efficiency (WR) of the separated water were 90.2 ± 1.8% and 94.82 ± 0.95%, respectively, in the emulsion-0.2 (containing 0.2% crude oil). When the dosage was 200 mg/L, the WT and WR values of the emulsion-1 (with 1% crude oil) were 91.9 ± 0.9% and 99.14 ± 0.1%, respectively. In addition, dynamic interfacial tension (IFT), wettability, zeta potential, interfacial activity and adsorption capability of RH-NH2 at the interface were also investigated. The results showed that the IFT values of asphaltene and RH-NH2 (200 mg/L) was 22.58 mN/m and 16.42 mN/m, respectively. The zeta potential of the O/W emulsion was − 37 ± 1.8 mV while that of RH-NH2 was 20.8 ± 1.0 mV, which facilitated the electrostatic neutralization and reduced the electrostatic repulsion between oil droplets. A possible demulsification mechanism was proposed, which indicated that RH-NH2 was amphiphilic, with high interfacial activity and stronger capability to reduce IFT. It migrated rapidly to the oil–water interface and disrupted the interfacial film via synergistic effect of the π-π/n-π interaction, leading to demulsification. RH-NH2 has a potential industrial application due to its low-cost and high demulsification efficiency. [ABSTRACT FROM AUTHOR]

Oily wastewater causes a lot of environment problems and draws wide attention. In this paper, titanium modified multi-walled carbon nanotubes (CNTs/TiO2) for the treatment of oily wastewater were synthesized using in situ sol-gel methods. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) were employed to characterize the structure and composition of CNTs/TiO2. Also, scanning electron microscope (SEM) and transmission electron microscope (TEM) showed that TiO2 was evenly distributed in carbon nanotubes (CNTs) to induce a good synergistic effect. After the oily wastewater was treated with 400 mg/L of CNTs/TiO2 at room temperature for 30 min, the light transmittance of the aqueous phase was 89.7%. Furthermore, the composites with good interfacial activity could be reused at least five times. The combination of dynamic interfacial tension measurements, interfacial activity, interfacial film assemble and optical microscope was employed to investigate the demulsification mechanism. [ABSTRACT FROM AUTHOR]

In the present study, a hyperbranched polymer demulsifier (PPDA) was synthesized by an improved "one‐pot" method with 1,4‐phenylene diamine as the central core, and ethylenediamine and methyl acrylate as the chain segments. NMR and Fourier transform infrared spectroscopy were used to confirm the molecular structure of the demulsifier, and thermogravimetric analysis was carried out to estimate its thermal stability. The effects of some important experimental parameters such as concentration, temperature and settling time on the demulsification performance were systematically studied. The results demonstrated that the light transmittance and oil removal ratio of oily wastewater reached to 47.9 % and 93.62 %, respectively, after demulsification with 20 mg.L−1 PPDA for 30 min at room temperature. With the same concentration and time at 60 °C, the light transmittance and oil removal ratio reached 57.0 % and 96.35 %, respectively. In addition, PPDA showed high salt tolerance over 10000 mg.L−1. The possible demulsification mechanism was examined by comparing the demulsification performance of different demulsifiers in diesel emulsion and oily wastewater, respectively. Furthermore, surface tension, interfacial tension, zeta potential and micrograph measurements provided convincing evidence for the possible demulsification mechanism. The surface tension reduction was 29.86 and 31.75 mN.m−1 at 25 °C and 60 °C, respectively. The corresponding critical micelle concentration was 4.17×10−7 and 5.50×10−7 mol.L−1, respectively. Additionally, the interfacial tension decreased from 15.70 to 6.96 mN.m−1 as the PPDA concentration increased from 20 mol. L−1 to 100 mol. L−1. This showed that PPDA easily absorbed at the interface and rapidly permeate into the interface film and then to broke the oil droplets. This work provides a new hyperbranched polymer demulsifier for the treatment of oily wastewater and is beneficial for understanding the demulsification mechanism. [ABSTRACT FROM AUTHOR]

[Display omitted] • RHC-0.5 was prepared via a simple one-step hydrothermal route. • RHC-0.5 has high demulsification efficiency in water-in-crude oil. • The demulsification efficiency of RHC-0.5 is similar to commonly commercial demulsifiers. • RHC-0.5 is low-cost and environmentally-friendly and easily prepared. Demulsification of crude oil emulsions still face many difficulties in the petroleum industry. Therefore, it is very important to develop innovative materials to achieve the effective separation of oil–water emulsions. In this work, an environmentally friendly RHC-0.5 demulsifier was prepared via a simple one-step hydrothermal route using rice husk (RH) as raw materials. It was characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, energy dispersive X-ray spectrometer and thermogravimetric analysis. The possible breaking mechanism was analyzed by particle size analysis, Zeta potential, interfacial activity, interfacial tension, self-assemble of interfacial film and microscopic analysis. The influence of some important factors such as dosage, temperature, standing time and salinity on the demulsifying efficiency (DP) was explored through bottle tests. The optimal DP of 95.01 % could be obtain with 300 mg/L of RHC-0.5 at 70 °C for 10 min. Meanwhile, RHC-0.5 had a good salt tolerance even at the salinity of 40000 mg /L. In addition, its DP was compared with that of commercial demulsifiers such as SP169, CH-66 and AR-32. This work not only can promote the efficient utilization of biological waste (RH), but also provides an insight into the exploration of new demulsifying materials with excellent performance. [ABSTRACT FROM AUTHOR]

• Coequally wetted composite materials are prepared via ultrasonication method. • Degradable and environmentally friendly β-CD and MCNT used for the synthesis. • MCNT@β-CD exhibit excellent interfacial activities. • An ultra-low concentration of MCNT@β-CD is utilized to break oily wastewater. • The separated water phase is similar to the distilled water. Emulsified oily wastewater has caused many problems in industrial production and ecological environment. To address this challenge, carbon nanotubes grafted with β-cyclodextrin (MCNT@β-CD) was prepared by an ultrasonic method to break oily wastewater. The composite materials were characterized by Fourier transform infrared spectroscopy, UV-visible spectroscopy, scanning electron microscope and thermogravimetric analysis. The demulsification test showed that the light transmittance of the resulting water phase was up to 94.5% at a low concentration of 50 mg/L within a few minutes at room temperature. Also, the corresponding oil remove rate was about 99.76%. In addition, it was suitable for acidic and neutral conditions with good salt tolerance. Interfacial activity, wettability, self-assembly at oil/water interface (WOI), dynamic interfacial tensions, zeta potential and photomicrograph were further investigated to confirm the possible mechanism. Generally speaking, the surface wettability of carbon nanotubes could be turned with β-CD. Therefore, MCNT@β-CD might rapidly migrate to WOI and replace the asphaltenes by π–π interactions and reduce the emulsion stability by charge neutralization. The current work provides a significant understand for the demulsification mechanism and indicates that MCNT@β-CD is a favorable interfacial activity, high demulsification efficiency and non-toxic demulsifier for oily wastewater. [ABSTRACT FROM AUTHOR]

In order to reduce the cost of demulsifiers and improve the demulsification performance of carbon material demulsifier, the nano-SiO 2 was grafted onto the surface of oxidized carbon black (Ox-CB) by sol-gel method in current study. The novel composite demulsifier was analyzed by fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscope (FE-SEM), energy dispersive X-ray (EDX) and X-ray diffraction spectra (XRD) which confirmed the partial grafting of SiO 2 on the oxidized carbon black (Ox-CB).The influences of temperature, settling time, and concentration of the composite demulsifier on the efficiency for breaking up water-in-oil emulsions were investigated in detail by bottle test. It was found that the best operating conditions to remove more than 90% of the water from the original emulsion were a temperature of 75 ℃ and a demulsifier concentration of 500 mg/L. The wettability, oil-water interfacial tensions (IFT) and interfacial activity of the demulsifier were further measured to explore the demulsification mechanism. Possible demulsification mechanism showed that the composite demulsifier could lead to the breakup of water-in-oil emulsions by bridging, flocculation and coalescence. The high interfacial activity is the main factor affecting the demulsification. [ABSTRACT FROM AUTHOR]

A femtosecond laser is used to break and exfoliate two dimensional (2D) flakes of nitrogen-doped graphene oxide (NGO) or molybdenum disulfide (MoS 2) dispersed in acetonitrile or a 1:1 ethanol-water mixture and convert them into nanoparticles (NPs) in 70–100 min. The chemically active NPs bond with atoms from the laser-dissociated acetonitrile or ethanol and water molecules to form 2D NPs functionalized with varying quantities of nitrogen, oxygen, hydrogen, and carbon groups. Sensitive and selective detection of heavy metal ions (HMI) Hg2+, As3+, Pb2+, and Cd2+ is demonstrated with the solvent-functionalized NGO and MoS 2 NPs. Binding between the HMI and functional groups leads to quenching of the NPs' photoluminescence. Limits of detection of 3 n m (Hg2+), 3.8 n m (As3+), 1.8 n m (Pb2+), and 13 n m (Cd2+) are demonstrated with the solvent-functionalized NGO in acetonitrile, NGO in acetonitrile, MoS 2 in acetonitrile, and NGO in ethanol-water, respectively. The selectivity is attributed to varying bond polarities associated with the different combinations of NPs and functional groups, which electrostatically attract HMI with different affinities. The functional groups responsible for the selective sensing in the different NP solutions are identified using Fourier transform infrared spectroscopy. This rapid, one-pot, room-temperature process can be used to tailor 2D materials for targeted chemical sensing. • A femtosecond laser is used to synthesize and functionalize nanoparticles of MoS 2 and nitrogen-doped graphene oxide. • The laser treatment is a one-pot, room-temperature process that takes only 70 mins. • Sensitive and selective detection of Hg2+, As3+, Pb2+, and Cd2+ ions based on fluorescence quenching is demonstrated. • Limits of detection are < 15 nanomolars for all ions. • Specific functional groups responsible for the selectivity are identified. [ABSTRACT FROM AUTHOR]

A low cost and environmentally friendly demulsifier (A-RS) was prepared using waste rice straw (RS) as starting materials via a simple acid treatment process. It was characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectrometer (EDS), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The influence of demulsifier dosage, temperature, settling time, pH value and salinity on the demulsification efficiency (DE) of water-in-crude oil emulsion were explored through bottle tests. The results displayed that the DE could reach 89.52% within one minute when the dosage of A-RS was 600 mg/L at 70 °C. The A-RS demulsifier had a good acid and alkali resistance, the DE could reach 92.72% and 86.32% when the pH value of emulsion was 2 and 10, respectively. Also, it had an excellent salt tolerance, and the DE increased slightly with the increase of the salinity. The demulsification mechanism was also investigated through interfacial activity, interfacial tension (IFT), wettability, formation of interfacial film and optimal microscopy. It is expected that A-RS has a great application prospect in the dehydration of crude oil. [Display omitted] • Rice straw (RS) is readily available and low-cost. • A-RS is obtained by a dilute acetic treatment process at room temperature. • The preparation method is very simple and safe. • The demulsification efficiency of A-RS reaches 89.52% within 1 min. [ABSTRACT FROM AUTHOR]