Amine-functionalized cotton for the treatment of oily wastewater.

Common commercial demulsifiers are typically made from ethylene oxide and propylene oxide. The production process is dangerous and complex, with poor adaptability and high cost. In this work, cotton modified with polyethylene polyamine was utilized as a demulsifier for the treatment of oily wastewater. The chemical structure and morphology of the as-prepared sample (CPN) were characterized by IR spectrum and SEM. The effect of CPN dosage, pH value, and salinity on the demulsification performance of oily wastewater was explored through the bottle tests. The results showed that the light transmittance of separated water was 81.7% and the corresponding deoiling rate was 98.5% when a CPN dosage of 25 mg/L was used at room temperature for 30 min. The interfacial properties were also systematically investigated, and the results indicated that CPN had better interfacial activity and a stronger reduction capability of interfacial tension compared to asphaltenes. The finding initiated and accelerated the demulsification process of oily wastewater. Based on the outstanding performance of this biomass-derived demulsifier, it shows promising potential for application in the treatment of oily wastewater.

Diethylenetriamine modified biological waste for disposing oily wastewater.

Oily wastewater produced in the process of oil extraction has a potential threat to the environment. In this paper, diethylenetriamine was used to modify rice straw powder (RSP) by a solvent-free strategy, and the obtained product (AM-RSP) was utilized to dispose oily wastewater. AM-RSP was characterized by Field emission scanning electron microscope (FE-SEM), energy dispersive spectrometer (EDS), Fourier transform infrared spectroscope (FT-IR) and BET. The factors affecting the demulsification performance (DP) such as dosage, salinity and pH value were detailly investigated. The results indicated that light transmittance (ET) and oil removal rate (ER) of separated water could reach 93.5% and 96.5%, respectively, within 40 min with 150 mg/L of AM-RSP at room temperature. Also, AM-RSP had a good salt resistance. In addition, three-phase contact angle (TCA), formation of interfacial film, interfacial activity, dynamic interfacial tension (IFT), coalescence time of droplets and zeta potential were adopted to probe the demulsification mechanism.

Synthesis and demulsification performance of a novel low-temperature demulsifier based on trimethyl citrate.

A significant amount of water-in-oil (W/O) emulsion is generated during petroleum extraction. However, the current commercial demulsifiers are expensive to produce and requires high demulsification temperatures, leading to increased energy and economic consumption. To enhance the efficiency of demulsifiers and reduce the cost of demulsifying W/O emulsions, we have successfully developed a novel demulsifier named TCED through a straightforward two-step process. This demulsifier features trimethyl citrate as the hydrophilic core grafted with three hydrophobic chains. Its structure was characterized using EA, FT-IR and 1H NMR spectroscopy, and the demulsification performance was comprehensively evaluated. At a low demulsification temperature of 40 °C, TCED demonstrated a remarkable demulsification efficiency (DE) of 99.06% and 98.74% in emulsions containing water contents of 70% (E70) and 50% (E50), respectively. Especially, a DE of 100% could be obtained in both E70 and E50 emulsions at a concentration of 600 mg/L. Moreover, TCED displayed a high DE even at high salinity levels of 50,000 mg/L and across a wide pH range of 2-10. Additionally, the phase interface was consistently clear after demulsification. To investigate the demulsification mechanism of TCED, various adsorption kinetics experiments were conducted, including measurements of interfacial tension (IFT), surface tension (SFT), interfacial competitive adsorption, and stability of interfacial film. The results obtained from the experiments indicated that TCED possessed remarkable diffusion and replacement capabilities within the emulsions. As a result, it effectively disrupted the original interfacial active substances, such as asphaltenes aggregates found in crude oil. TCED exhibits a high DE at low concentration and temperature. This characteristic highlights its significant potential for low-temperature demulsification applications in the petroleum industry.

Sustainable remediation of Cr(VI)-contaminated soil by soil washing and subsequent recovery of washing agents using biochar supported nanoscale zero-valent iron.

Soil contamination by Cr(VI) has attracted widespread attention globally in recent years, but it remains a significant challenge in developing an environmentally friendly and eco-sustainable technique for the disposal of Cr(VI)-contaminated soil. Herein, a sustainable cyclic soil washing system for Cr(VI)-polluted soil remediation and the recovery of washing agents using biochar supported nanoscale zero-valent iron (nZVI-BC) was established. Citric acid (CA) was initially screened to desorb Cr(VI) from contaminated soil, mobilizing Cr from the highly bioaccessible fractions. The nZVI-BC exhibited superior properties for Cr(VI) and Cr(total) removal from spent effluent, allowing effective recovery of the washing agents. The elimination mechanism of Cr(total) by nZVI-BC involved the coordinated actions of electrostatic adsorption, reduction, and co-precipitation. The contributions to Cr(VI) reduction by Fe0, surface-bound Fe(II), and soluble Fe(II) were 0.6 %, 39.8 %, and 59.6 %, respectively. Meanwhile, CA favored the activity of surface-bound Fe(II) and Fe0 in nZVI-BC, enhancing the production of soluble Fe(II) to strengthen Cr(VI) removal. Finally, the recovered washing agent was proven to be reused three times. This study showcases that the combined soil washing using biodegradable chelant CA and effluent treatment by nZVI-BC could be a sustainable and promising strategy for Cr(VI)-contaminated soil remediation.

Synthesis and demulsification mechanism of an ionic liquid with four hydrophobic branches and four ionic centers.

Stable emulsions can have numerous negative impacts on both the oil industry and the environment. This study focuses on the synthesis of two ionic liquids (via. PPBD and PPBH) with four hydrophobic branches and four ionic centers that can effectively treat oil-water emulsions at a low temperature of 40 °C. Their chemical structure was explored using Fourier-transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance hydrogen spectra (1H NMR). The effect of temperature, PPBD and PPBH concentration, oil-water ratio, salinity and pH value on the demulsification efficiency (DE) of W/O emulsion was studied detailly and several commercial demulsifiers were also used for comparison. Results revealed that by adding 250 mg/L of PPBH in an E30 emulsion and leaving it for 120 min at 40 °C, the DE could reach 96.34%. Meanwhile, in an E30 emulsion (oil-water mass ratio of 3:7) with 250 mg/L of PPBD, the DE of 95.23% could be obtained at 40 °C for 360 min. Especially, the DE of PPBH could reach 100% in an E70 emulsion (oil-water mass ratio of 7:3) at the same conditions. Additionally, the demulsifier (PPBH) exhibited excellent salt resistance and outperformed some commonly used commercial demulsifiers. Several methods were utilized to investigate the potential demulsification mechanism, including measuring interfacial tension (IFT), three-phase contact angle (CA), droplet contact time, zeta potential, and observing samples under optical microscopy.

Preparation of a demulsifier for oily wastewater using thorn fir bark as raw materials via a hydrothermal and solvent-free amination route.

In current work, a TB-EDA demulsifier for disposing oily wastewater was prepared using thorn fir bark (TB) as starting materials via a hydrothermal and solvent-free amination route. Field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectrometer (EDS), and Fourier transform infrared spectroscope (FT-IR) were employed to characterize the TB-EDA demulsifier. Three-phase contact angle (CA), interfacial activity, formation of interfacial film (FIF), coalescence time of droplets (CTD), dynamic interfacial tension (IFT), and Zeta potential were carried out to study the possible demulsification mechanism. Bottle test was performed to investigate the effect of the TB-EDA dosage, salinity, and pH value on the demulsification performance at room temperature. Light transmittance (DL) and oil removal rate (DR) of separated water were 94.7% and 97.2%, respectively, with 100 mg/L of TB-EDA demulsifier in oily wastewater at room temperature. In addition, the TB-EDA demulsifier has an excellent salt tolerance even at the salinity of 50,000 mg/L. The corresponding DL and DR could reach 99.8% and 99.9%, respectively.

Demulsification of oily wastewater using a nano carbon black modified with polyethyleneimine.

In this work, nano carbon black was modified with polyethyleneimine (CB-PEI) under an ultrasonic field. The obtained product was used as a demulsifier to break oily wastewater. Morphology, structure, and chemical composition of CB-PEI were systematically analyzed. Bottle test was carried out to evaluate the influence of dosage, pH value and salinity on the demulsification efficiency of the emulsion. The results showed that the light transmittance of water phase (TSW) after the demulsification was 79.1% and corresponding oil removal rate (ORR) could reach up to 99.4% with 60 mg/L of CB-PEI at ambient temperature for 30 min. In addition, the possible demulsification mechanism was explored by dynamic interface tension (IFT), elasticity modulus, wettability, self-assemble of interfacial membrane, zeta potential and micrograph analysis. It indicated that CB-PEI had an appropriate amphiphilicity and good interfacial activity, which could improve it quickly transfer to the oil-water interface and result in the oil-water separation. The current work provides a simple method to prepare a demulsifier with excellent performance, so it has a good application prospect for the treatment of oil-water emulsions.

Recyclable amine-functionalized carbon nanotubes for the separation of oily wastewater.

In this work, a CNTs-NH2 demulsifier was prepared by grafting ethylenediamine on the surface of carbon nanotubes to break oily wastewater. The physicochemical and interfacial properties of CNTs-NH2 were characterized and analyzed. It showed that CNTs-NH2 had an eminent amphipathicity and high interfacial activity, which allows it to sharply migrates to the interface and effectively interacts with interfacial film by the combined action of π-π interaction and electrostatic attraction. The demulsification tests exhibited that CNTs-NH2 could effectively remove emulsified oil from the oily wastewater. It could be used at acidic and neutral conditions, and high salinity. Moreover, it could be recycled and still maintained its interfacial activity, thusly vastly enhancing the application scope. The light transmittance was up to 88.1% and the corresponding oil removal rate was 99.2% with 100 mg/L of CNTs-NH2 for 30 min. The oil removal rate of CNTs-NH2 remained above 97.8% after 6 cycles. This work provides a deep understanding on the design of demulsifier and its demulsification mechanism.

Demulsification of water-in-crude oil emulsion driven by a carbonaceous demulsifier from natural rice husks.

Removing emulsified water from a water-in-crude oil (W/O) emulsion is critically required prior to downstream processing in the petroleum industry. In this work, environmentally friendly and amphipathic rice husk carbon (RHC) demulsifier was prepared by a simple carbonization process in a muffle furnace using rice husks as starting materials. RHC was characterized by field-emission scanning electron microscope, energy dispersive spectrometer, Fourier transform infrared spectrometer, ultraviolet-visible spectrometer, powder X-ray diffraction, zeta potential and synchronal thermal analyzer. The factors such as dosage, temperature, settling time, pH value and salinity were systematically investigated. The results indicated that the dehydration efficiency (DE) reached as high as 96.99% with 600 mg/L of RHC for 80 min at 70 °C. RHC exhibited an optimal DE under neutral condition, but it was also effective under acidic and alkaline conditions. Also, it had an excellent salt tolerance. The possible demulsification mechanism was explored by interfacial properties, different treatment methods for RHC and microexamination. The demulsification of RHC is attributed to its high interfacial activity, oxygen-containing groups and content of silica. It indicates that RHC is an effective demulsifier for the treatment of the W/O emulsion.

Demulsification of amphiphilic gemini ionic liquids and its demulsification mechanism.

This work aims to prepare two new amphiphilic and interfacial active gemini ionic liquids to treat crude oil and investigates its demulsification mechanism. Tetraethylene glycol was pretreated with thionyl chloride and used as a linker to connect succinimide or phthalimide, and then reacted with dodecyl benzene sulphonic acid to obtain the corresponding amphiphilic and interfacial active gemini ionic liquid STA or PTA, respectively. 1H nuclear magnetic resonance spectroscopy (1HNMR) and Fourier-transform infrared spectroscopy (FTIR) was used to determine the chemical structures. The demulsification tests showed the demulsification efficiency with 150 mg/L of STA or PTA at 60 °C for 30 min was 99.89% and 99.79%, respectively. Furthermore, the demulsification mechanism of STA and PTA were studied and the prominent demulsification ability of STA and PTA were attributed to the better interfacial activity and amphipathy which could destroy the asphaltenes interfacial film. These results showed that STA and PTA had excellent demulsification efficiency, which promised application in petroleum industry.

Nanoscale silica-coated graphene oxide and its demulsifying performance in water-in-oil and oil-in-water emulsions.

In current work, GO@SiO2 nanocomposite was prepared by coating nanoscale silica onto graphene oxide (GO). GO@SiO2 was characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (IF-IR). Additionally, the demulsifying performance of GO@SiO2 was investigated by bottle test. The results showed that GO@SiO2 had a good demulsifying performance in both oil-in-water (O/W) and water-in-oil (W/O) emulsions. When the concentration of GO@SiO2 was 200 ppm in the O/W emulsion, the optimal light transmittance of aqueous phase (LTA) and corresponding oil removal rate (ORR) at room temperature could reach 86.9% and 99.48%, respectively. Also, GO@SiO2 had an excellent salt tolerance under acidic condition. Furthermore, GO@SiO2 also could demulsify the W/O emulsion, and the efficiency at 70 °C could reach 80.5% when the concentration was 400 ppm.