Multi-functional magnetic bacteria as efficient and economical Pickering emulsifiers for encapsulation and removal of oil from water

Promising application of probiotic microorganisms as Pickering emulsions stabilizers

The purpose of this work was to study the ability of nineteen food-grade microorganisms as Pickering emulsion (PE) stabilizers. Medium-chain triacylglycerol (MCT) oil-in-water (50:50) PEs were fabricated by 10 wt% or 15 wt% of thermally-inactivated yeast, cocci, Bacillus spp. and lactobacilli cells. The characteristics of microorganisms related to "Pickering stabilization" including morphology, surface charge, interfacial tension, and "contact angle" were firstly studied. After that, the cells-stabilized PEs were characterized from both kinetic and thermodynamic viewpoints, microstructure and rheological properties. The interfacial tension and "contact angle" values of various microorganisms ranged from 16.33 to 38.31 mN/m, and from 15° to 106°, respectively. The mean droplet size of PEs ranged from 11.51 to 57.69 µm. Generally, the physical stability of cell-stabilized PEs followed this order: lactobacilli > Bacillus spp. > cocci > yeast. These variations were attributed to the morphology and cell wall composition. Increasing the microorganism concentration significantly increased the physical stability of PEs from a maximum of 12 days at 10 wt% to 35 days at 15 wt% as a result of better interface coverage. Shear-thinning and dominant elastic behaviors were observed in PEs. Physical stability was affected by the free energy of detachment. Therefore, food-grade microorganisms are suggested for stabilizing PEs.

The degradation of high emulsified oil wastewater in an intermittently-aerated MBBR packed with magnetic polystyrene particles

This work aims to explore the effects of the magnetic polystyrene particles (MPS) on contaminants removal of the high emulsified oil wastewater. 26 days intermittently-aerated progress illustrated that COD removal efficiency and the resistance to the shock loading was promoted in the presence of MPS. Gas chromatography (GC) results also indicated that MPS enhanced the number of organic species reduced. According to the cyclic voltammetry test, conductive MPS appeared special redox performance which was considered could to facilitate the extracellular electron transfer. Furthermore, MPS dosing accelerated the electron-transporting system (ETS) activity by 24.91% compared the control. Based on the superior performance above, the conductivity of MPS is considered to be responsible for the enhanced organic removal efficiency. Moreover, the high-throughput sequencing displayed that electroactive Cloacibacterium and Acinetobacter accounted for a higher proportion in the MPS reactor. Additionally, Porphyrobacter and Dysgonomonas which were capable of degrading organics were also enriched more by MPS. To sum up, MPS is a promising additive to enhance the organic substances removal for the high emulsified oil wastewater.

Preparation of asymmetric Janus hollow silica microparticle and its application on oily wastewaters

Janus nanoparticles have aroused the interest of scholars because of their highly efficient emulsification of spilled oils in wastewater. In this work, interfacially active Janus hollow glass microparticles (J-HGMPs) of asymmetric wettability were designed and synthesized in order to achieve more efficient separation of emulsified oil droplets from oily wastewater. Surface characteristic techniques such as FTIR, SEM, zeta potential and contact angle measurements had been employed to assess the amphiphilic surface properties of J-HGMPs. The oil removal/recovery performance of J-HGMPs in different oil-water systems and their interfacial activities were studied. As a particulate emulsifier, J-HGMPs could remove/recover > 96% oil from oil-water mixed phase. The results showed that J-HGMPs had strong interfacial activities and anchored firmly at oil/water interfaces. This high adsorption energy was also evaluated and verified via the calculation of Gibbs free energy. Overall, this study provided a novel and low-cost oil recovery method via a convenient buoyancy force that could be effectively applied in the treatment of oil spills while achieving the goal of benign and green environmental protection.

Demulsification Performance and Mechanism of Tertiary Amine Polymer-Grafted Magnetic Nanoparticles in Surfactant-Free Oil-in-Water Emulsion

Numerous cationic magnetic nanoparticles (MNPs) have previously been developed for demulsifying oil-in-water (O/W) emulsion, and results showed that the cationic MNPs could effectively flocculate and remove the negatively charged oil droplets via charge attraction; however, to the best of our knowledge, there are no research reports regarding the synergetic influence of both the positive charge density and interfacial activity of MNPs on the demulsification performance. In this study, three tertiary amine polymer-grafted MNPs, namely, poly(2-dimethylaminoethyl acrylate)-grafted MNPs (M-PDMAEA), poly(2-dimethylamino)ethyl methacrylate)-grafted MNPs (M-PDMAEMA), and poly(2-diethylaminoethyl methacrylate)-grafted MNPs (M-PDEAEMA), were synthesized and evaluated for their demulsification performance. Results demonstrated that a high positive charge density and superior interfacial activity of MNPs could cause partial oil droplet re-dispersion when excessive MNPs were introduced, leading to a lower magnetic separation efficiency and narrower demulsification window. Herein, a demulsification window is defined as a range of nanoparticle dosages in which the MNPs can effectively demulsify the O/W emulsion under certain conditions. For highly positively charged MNPs, their good interfacial activity could aggravate the formation of a narrower demulsification window. When tertiary amine polymer-grafted MNPs carried a lower positive charge density or weak interfacial activity, that is, M-PDMAEA at pH 4.0, M-PDMAEMA at pH 5.0-9.0, and M-PDEAEMA at pH 9.0-10.0, wide demulsification windows were observed. Additionally, a recycling experiment suggested that MNPs could maintain high demulsification efficiency up to at least five cycles, indicating their satisfactory recyclability. The three tertiary amine polymer-grafted MNPs can be potentially used for efficient demulsification from surfactant-free O/W emulsion in various pH ranges.

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 (E_T) and oil removal rate (E_R) 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.

Kinetic and statistical perspectives on the interactive effects of recalcitrant polyaromatic and sulfur heterocyclic compounds and in-vitro nanobioremediation of oily marine sediment at microcosm level

A halotolerant biosurfactant producer Pseudomonas aeruginosa strain NSH3 (NCBI Gene Bank Accession No. MN149622) was isolated to degrade high concentrations of recalcitrant polyaromatic hydrocarbons (PAHs) and polyaromatic heterocyclic sulfur compounds (PASHs). In biphasic batch bioreactors, the biodegradation and biosurfactant-production activities of NSH3 have been significantly enhanced (p < 0.0001) by its decoration with eco-friendly prepared magnetite nanoparticles (MNPs). On an artificially contaminated sediment microcosm level, regression modeling and statistical analysis based on a 2³ full factorial design of experiments were trendily applied to provide insights into the interactive impacts of such pollutants. MNPs-coated NSH3 were also innovatively applied for nanobioremediation (NBR) of in-vitro diesel oil-polluted sediment microcosms. Gravimetric, chromatographic, and microbial respiratory analyses proved the significantly enhanced biodegradation capabilities of MNPs-coated NSH3 (p < 0.001) and the complete mineralization of various recalcitrant diesel oil components. Kinetic analyses showed that the biodegradation of iso- and n-alkanes was best fitted with a second-order kinetic model equation. Nevertheless, PAHs and PASHs in biphasic batch bioreactors and sediment microcosms followed the first-order kinetic model equation. Sustainable NBR overcome the toxicity of low molecular weight hydrocarbons, mass transfer limitation, and steric hindrance of hydrophobic recalcitrant high molecular weight hydrocarbons and alkylated polyaromatic compounds.

Treatment of oil-based drilling cuttings using the demulsification separation-Fenton oxidation method

In this study, demulsification separation-Fenton oxidation technology was employed as a combined technology to treat total petroleum hydrocarbons (TPH) in oil-based drill cuttings (OBDC). Batch experiments were carried out to optimize the technology parameter. Under the optimal condition, 70% and 51% TPH removal rate was obtained for demulsification technology and Fenton oxidation technology, respectively. Eighty-five percent of TPH removal rate was obtained using combination technology of demulsification separation and Fenton oxidation. Multiple characterizations were used to analyze the physical and chemical properties of treated OBDC. The result of XRD pattern indicated the combination technology had no obvious effect for structure phase of OBDC. The results of FTIR, GC-MS, TG-DTG and SEM were used to characterize the treated OBDC. This paper provides an efficient and feasible combined technology for OBDC treatment, which expands a new strategy for the removal of TPH from solid waste.

Removal of emulsified oil from water by using recyclable chitosan based covalently bonded composite magnetic flocculant: Performance and mechanism

In this work, a novel recyclable covalently bonded magnetic flocculant (FS-MC) was successfully prepared by combining chitosan-based modified polymers (MCS) with Fe₃O₄@SiO₂ through a silane coupling agent. The covalent bond Fe-O-Si-O-C and the core-shell structure of FS-MC were confirmed through several characterization methods. The emulsified oily wastewater flocculation performance and mechanism by using FS-MC were evaluated and studied. Results showed that 94.47%, 93.95%, and 92.98% of emulsified oil could be removed by using FS-MC1, FS-MC2 and FS-MC3 at dosages of 2.0, 2.5, and 2.0 mg/L, respectively. Furthermore, FS-MC exhibited an excellent behavior on the removal of organic compounds with molecular weight > 10 kDa, including long chain alkanes, cycloalkanes, and aromatic hydrocarbon compounds. In addition, triple-phase separation of oil, water and flocculants was achieved by using magnetic FS-MC. Due to the introduction of cationic and hydrophobic groups in FS-MC, charge neutralization, compression double electric-layer action, hydrophobic interaction, interfacial adsorption bridging and sweep-flocculation synergistically contributed and enhanced the removal of emulsified oil. Recycling experiments also showed that no obvious decrease of oil removal rate was observed by using magnetic FS-MC flocculants in five cycles.

Inter-droplet force between magnetically polarizable Pickering oil-in-water nanoemulsions stabilized with γ-Al2O3 nanoparticles: Role of electrostatic and electric dipolar interactions

HYPOTHESIS

The presence of nanoparticles at oil-water interface influences the interaction forces between Pickering emulsions. When charged nanoparticles are at the oil-water interface of an electrostatically stabilized emulsion, in addition to the screened Coulombic interaction, electric dipolar force also influences the total inter-droplet force profiles. An in-depth understanding of the effects of such electric dipolar forces is essential for designing colloidally stable Pickering nanoemulsions for various applications.

EXPERIMENTS

Inter-droplet forces between γ-Al₂O₃ nanoparticle stabilized oil-in-water nanoemulsion, containing superparamagnetic nanoparticles (magnetically polarizable) in the oil phase, are measured using the magnetic-chaining technique at different pH and salt concentrations. The role of mono-, di- and tri-valent salts on the inter-droplet force profiles are assessed.

FINDINGS

Force measurement studies reveal a lowering of inter-droplet spacing, within the linear chains, for higher salt concentrations due to an increased screening. Strong interfacial attachment of the charged nanoparticles results in the formation of an asymmetric charge cloud leading to an electric dipolar interaction. Incorporating the contributions of electric dipolar and screened Coulombic interactions, the theoretically estimated total repulsive force magnitudes are in good agreement with the experimental data. The obtained results offer better insights into the nature of colloidal force between charged particle stabilized nanoemulsions.

Synthesis of Bacteria Imprinted Polymers by Pickering Emulsion Polymerization

Molecularly imprinted polymers have been studied for a long time and have found useful applications in many fields. In most cases, small organic molecules are used as templates to synthesize imprinted polymers. In contrast to low molecular weight targets, large biological molecules and cells are more challenging to use as templates to synthesize cell-recognizing materials. This chapter presents an interfacial imprinting method to synthesize bacteria-recognizing polymer beads using Pickering emulsion polymerization. The tendency of bacteria to reside between two immiscible liquids is utilized to create surface-imprinted binding sites on cross-linked polymer microspheres.