No abstract

In this study, an effective and environmentally friendly polyaminated cross-linked chitosan (M-PACTS) flocculant was successfully synthesized via circular focus single-mode microwave synthesizer irradiation. Epichlorohydrin and tetraethylenepentamine were used as the cross-linking agent and active cationic reagent, respectively. The same formation was used to prepare cationic lightly cross-linked chitosan (C-PACTS) via the conventional heating method. The flocculant was characterized using Fourier transform infrared spectroscopy, X-ray diffraction analysis, and scanning electron microscopy. The flocculation capability of C-PACTS and M-PACTS was compared using laundry wastewater as a model pollutant. The pH, PACTS dosage, temperature, stirring rate, stirring time, and setting time were systematically investigated. The experimental results showed that circular focus single-mode microwave synthesizer irradiation was a more efficient method to modify chitosan. M-PACTS exhibited a higher capacity for turbidity and chemical oxygen demand (COD Cr ) removal. Under optimal conditions, the removal rate values of M-PACTS were up to 96% (turbidity) and 78% (COD Cr ). The proposed PACTS is suitable for treatment of polluted wastewater in an eco-friendly manner without causing secondary pollution.

Low porosity and permeability of oil and gas reservoirs make it difficult to develop these resources. To address these problems, we developed and evaluated a novel, environmentally friendly waterproof locking agent, which was prepared using dimethyl silicone oil and octadecyltrimethylammonium chloride and characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and particle size measurement. The waterproof locking performance of the agent was evaluated in a low-permeability reservoir using surface tension and contact angle measurements, and thermodynamic calculations were performed. The average particle size or median diameter ( D 50 ) of a 1% mother liquor was 325 nm at 20 °C and 470.8 nm at 70 °C. The contact angle of clean water on the core surface increased from 10 to 110°. At 70 °C, the surface tension of water was reduced to 24 mN·m –1 , indicating good waterproof locking performance. The interaction parameters were calculated in accordance with the Langmuir adsorption theory. The increase in temperature from 20 to 70 °C reduced Γ max from 4.59 × 10 –6 to 1.36 × 10 –6 mol·m –2 and Δ G θ from −40.93 to −56.54 kJ·mol –1 . Thus, the adsorption behavior of the developed locking agent is believed to improve the productivity of oil wells.

Surfactants are widely used in enhanced oil and gas recovery. Surfactants are usually injected into wells and reservoirs that are released in full upon the addition, and effectiveness lasts very short. Slow‐release surfactant is preferred to be effective at an extended period. In this study, surfactant was encapsulated into the crosslinked hybrid hydrogel of polyvinyl alcohol (PVA) and poly acrylamide‐2‐methyl propane sulfonic acid (PAMPS). The encapsulated surfactant was slow‐released at high temperatures. Free radical polymerization was used to polymerize acrylamide‐2‐methyl propane sulfonic acid and crosslink PVA in the presence of surfactant. The hybrid hydrogel complex was characterized by an infrared spectrum, electronic scanning microscope, and thermogravimetric analysis. The release profile of surfactant was studied in synthetic brine at 130°C. The results indicate that hybrid hydrogel encapsulated surfactant is stable and releases surfactant at high temperatures for more than 7 days. The diffusion of surfactant from hydrogel follows the zero‐order kinetic model.