Qinghong Wang

Gemini surfactants are extensively employed in enhanced oil recovery (EOR) owing to their low critical micelle concentration (CMC), excellent interfacial activity, and strong self–assembly capability. However, molecular–level understanding of how spacer chemistry regulates the interfacial behavior of sulfonate–containing gemini surfactants remains limited. All–atom molecular dynamics simulations were employed to investigate four gemini sulfonate surfactants with distinct spacers (carbon–chain spacer (CA), ester containing spacer (EG), benzene–ring spacer (BR), and nitrogen–containing (NA)) at the n–decane/water interface. Based on its superior interfacial performance, the EG system was further selected to evaluate the effects of polyacrylamide (PAM) and partially hydrolyzed polyacrylamide (HPAM). Increasing surfactant concentration markedly altered interfacial assembly, and at 2.33 μmol/m², pronounced interfacial curvature indicated a tendency toward microemulsion-like structures. Spacer chemistry strongly regulated interfacial thickness, hydration, and molecular organization. The rigid aromatic spacer of BR broadened the interfacial region through its strong oil–phase affinity, whereas the ester–containing EG spacer enhanced hydration and hydrogen–bond formation and promoted favorable molecular packing, resulting in the best overall interfacial performance. Further simulations showed that PAM accumulated near the EG interfacial layer and strongly interacted with EG, leading to a pronounced reduction in interfacial tension. In contrast, hydrolysis strengthened HPAM–water interactions and promoted its distribution in the bulk aqueous phase, thereby limiting its influence on the interface. This study provides molecular insights into how different spacer groups regulate interfacial behavior, offering theoretical guidance for the design and formulation of gemini surfactant systems for EOR.

Aerobic granular sludge (AGS) is promising for refractory pollutant removal, whereas its application is constrained by long start-up periods and insufficient structural stability. Quorum sensing (QS) modulates bacterial community behaviors and plays a pivotal role in AGS formation and stabilization. Using quinoline as the target pollutant, this study successfully cultivated AGS. Moreover, we linked acyl-homoserine lactones (AHL)-based QS dynamics to EPS quantity/composition shifts during quinoline-stressed granulation. During granulation, the concentration of AHLs (C4-HSL and C8-HSL) increased with a significant upregulation of AHL-associated synthesis genes (mainly rhlI) and sensing genes (especially cciR, sdiA and aphA). Quinoline-triggered QS altered the composition of EPS, raising EPS content from 12.5 mg/g VSS to 97.5 mg/g VSS and the PN/PS ratio to 2.3, indicating enhanced granulation and improved particle stability. Further analysis revealed that the enriched hydrophobic amino acids and monosaccharides in EPS enhanced relative hydrophobicity of AGS, reduced surface negative charge, and eliminated the energy barrier, ultimately strengthening microbial aggregation. Furthermore, exogenous addition of 1 μM C8-HSL effectively improved granule stability by regulating EPS biosynthesis. This work provides the first mechanistic evidence that AHL-mediated QS can be harnessed to improve AGS formation and resilience under toxic stress, by modulating EPS composition and microbial community.

Thermochemical washing of oily sludge is a highly effective strategy for resource recovery. However, the lingering petroleum components within washed sludge still pose considerable environmental pollution risks. In this study, high-temperature bioaugmentation technology was used to promote the removal of petroleum components, and the potential of this technology in the deep treatment of washed oily sludge was investigated, specifically petroleum component degradation and microbial community regulation. The results showed that the petroleum degradation performance was greatly enhanced by the introduction of thermophilic bacteria combined with 200 mg/kg of biosurfactant (T2 group). Under these conditions, the petroleum and moisture contents were successfully reduced to 19.6 g/kg and 4%, respectively. In particular, the contents of n-alkanes and polycyclic aromatic hydrocarbons in the T2 group decreased significantly to 1098.5 and 494.3 mg/kg, respectively, relative to the blank group (4428.5 and 850.7 mg/kg). High-throughput sequencing results indicated that exogenous thermophilic bacteria (Ureibacillus and Bacillus) could rapidly emerge as the dominant genera in the system. In addition, microbial association network and functional analyses revealed that high-temperature bioaugmentation shifted microbial interactions from competition to cooperation, as evidenced by increased positive correlation ratios and modularity values, as well as functional diversification from two modules in the blank group to four modules in the biofortified treatments, thereby enhancing synergistic degradation capabilities for hydrocarbons. This study provides a newly developed approach to oily sludge treatment that simultaneously achieves reduction and harmlessness.

Antibiotic pollution poses a serious environmental concern worldwide, posing risks to ecosystems and human well-being. Transforming waste activated sludge into adsorbents for antibiotic removal aligns with the concept of utilizing waste to treat waste. However, the adsorption efficiency of these adsorbents is currently limited. This study identified KOH modification as the most effective method for enhancing tetracycline (TC) adsorption by sludge biochar through a comparative analysis of acid, alkali, and oxidant modifications. The adsorption characteristics of TC upon unmodified sludge biochar (BC) as well as KOH-modified sludge biochar (BC-KOH) were investigated in terms of equilibrium, kinetics, and thermodynamics. BC-KOH exhibited higher porosity, greater specific surface area, and increased abundance of oxygen-based functional groups compared to BC. The TC adsorption on BC-KOH conformed the Elovich and Langmuir models, with a maximum adsorption capacity of 243.3 mg/g at 298 K. The adsorption mechanisms included ion exchange, hydrogen bonding, pore filling, and electrostatic adsorption, as well as π-π interactions. Interference with TC adsorption on BC-KOH was observed with HCO₃⁻, PO₄³⁻, Ca²⁺, and Mg²⁺, whereas Cl⁻, NO₃⁻, and SO₄²⁻ ions exhibited minimal impact on the adsorption process. Following three cycles of utilization, there was a slight 5.94% reduction in the equilibrium adsorption capacity, yet the adsorption capacity remained 4.5 times greater than that of unmodified sludge BC, underscoring its significant potential for practical applications. This research provided new insights to the production and application of sludge biochar for treating antibiotic-contaminated wastewater.