For optimizing the reaction conditions of 2-methyl-6-ethylaniline (MEA) degradation catalyzed by horseradish peroxidase (HRP), a response surface methodology with three factors and three levels was used in this research to establish a regression model, a ternary quadratic polynomial, in order to analyze temperature, H₂O₂ concentration and pH effects on MEA removal efficiency. The results showed that the regression model was significant (p < 0.0001), fitted well with experimental data and had a high degree of reliability and accuracy, and the data were reasonable with low errors. By analyzing interactions and solving the regression model, the maximum MEA removal efficiency was 97.90%, and the optimal conditions were defined as follows: pH 5.02, H₂O₂ concentration 13.41mM, and temperature 30.95 °C. Under the optimal conditions, the average MEA removal efficiency obtained from the experiments was 97.56%. This research can provide reference for the treatment of actual acetochlor industrial wastewater.

In order to obtain the optimal conditions for ammonia nitrogen (AN) wastewater treatment by bio filter (BF), the effects of ratio of carbon to nitrogen (C/N), pH, and hydraulic load (HL) on the AN degradation were studied by Response Surface Methodology (RSM). Central Composite Design (CCD) experiments were conducted, and the response of the AN removal rates were fitted to a second-order polynomial model. The analysis of variance showed that the model was accurate and reliable. Through model fitting, the optimal condition for AN removal was: C/N of 18.95, pH of 7.78, and HL of 1.04 d⁻¹. The maximum AN removal rate predicted by the model was 91.90%, accorded with the experimental verification value of 91.37% under the optimal condition. The research provided valuable demonstration for optimizing process parameters on AN removal in BF.

Hydrogels exhibit distinctive features. These properties make them suitable for applications across various fields, such as environment, energy, and medicine. In this paper, we conducted a comprehensive search on the CNKI and Web of Science databases spanning from 2000 to 2024. Using tools like CiteSpace and VosViewer, we visualized the evolution, composition, hot spots, and trends in hydrogels in the field of water treatment sustainability. The results show that from 2000 to 2024, there has been a gradual increase in the number of publications in this field. China leads in the total number of publications; although, it ranks fourth in average citation rate. Seven out of the top ten research institutions are based in China. Additionally, three journals, including the International Journal of Biological Macromolecules, Chemical Engineering Journal and Carbohydrate Polymers, stand out, with a relatively high number of publications. The identified research hotspots include a range of preparation methods, including the freezing method and cross-linking method. Additionally, other preparation methods and the examination of water retention rate and adsorption isotherm are part of the research focus. The primary emphasis is on studying the adsorption of heavy metals, microplastics, and organic pollutants in dye wastewater. The main adsorption mechanisms investigated are chelation, electrostatic attraction, and functional group interaction. These findings have potential applications in water purification, seawater desalination, and atmospheric condensation. For the authorized patents in hydrogel-related fields, with the continuous improvement in innovation ability and the continuous enhancement of intellectual property protection awareness, the number of authorized patents continues to rise. China has seven of the top ten institutions in the number of patents granted, and the total number of patents granted in China ranks first in the world. Future work should focus on methods for synthesizing new pollutants and other target pollutants and on improving adsorption efficiency. Additionally, the development of cost-effective hydrogel materials with improved treatment efficacy is essential to advance sustainable practices in water treatment.

In arid mountainous areas with stony soils in the Eastern Tibetan Plateau, intensively managed orchards (which include the need for plowing, irrigation, and soil stone removal), eco-forests, and grasslands, all converted from croplands, are becoming increasingly popular. We randomly collected soil samples at 0–15, 15–30, 30–45, and 45–60 cm depths from the four land-use types on the northern and southern slopes in the region. Differences in soil organic carbon (SOC) content/stock, soil water content (SWC), and rock fragment content (RFC) in land-use types and slopes were analyzed using two-way ANOVA. The factors’ contributions to SOC variation were assessed using mixed-effect models. Results showed the following: (1) In topsoil (0–30 cm), SOC contents followed the order eco-forest > orchard > grassland ≈ cropland; in subsoil (30–60 cm), the order was orchard > eco-forest > cropland ≈ grassland. SOC stocks (0–60 cm) were higher in orchards (93.72 Mg ha⁻¹) and eco-forests (92.44 Mg ha⁻¹) than in grasslands (53.65 Mg ha⁻¹) and croplands (53.05 Mg ha⁻¹). Contributions of SOC stocks at the 0–15 cm depth level to total SOC were above 40% for GL and EF and between 27 and 35% for OL and CL; at the 45–60 cm level, OL contributed 16–20% and was higher than 10–15% for the other land-use types. (2) Eco-forests and grasslands showed increased SOC contents/stocks at all soil layers on the northern slope than on the southern one. Orchards and croplands, however, showed no differences in contents between slopes. (3) Land-use types, TN, SWC, RFC, slope aspect, and management practices significantly affected SOC variation. Our results suggest that forest plantations (orchards and eco-forests) in arid mountainous regions, through active management practices (e.g., irrigation and fertilization), are vital for improving soil carbon sinks and achieving peak carbon/carbon neutrality goals.

A vertical-flow constructed wetland-microbial fuel cell (CW-MFC) was established with Acorus calamus as the wetland vegetation for rural domestic wastewater treatment under low-temperature winter conditions. Response surface methodology (RSM) coupled with central composite design (CCD) was used to optimize three key electrode parameters: electrode plate projection coefficient (PC), inter-electrode distance (ID), and external resistance (ER), and to evaluate their effects on COD removal efficiency. Compared with the standalone constructed wetland (CW), the CW-MFC system significantly improved wastewater treatment performance: the effluent COD concentration of the CW was 66.14 mg/L, exceeding the first-class discharge limit (60.00 mg/L) specified in the “Water Pollutant Discharge Standard for Rural Domestic Sewage Treatment Facilities” (DB51/2626–2019). In contrast, the effluent COD concentrations of the CW-MFC system ranged from 18.81 to 54.06 mg/L, all meeting the aforementioned first-class standard, with a significantly higher COD removal rate than the CW (P < 0.05). After electrode parameter optimization, the optimal configuration was determined as PC = 0.33, ID = 272.94 mm, and ER = 1619.31 Ω. Under these optimized conditions, the CW-MFC system achieved a COD removal efficiency of 89.14%, which was consistent with the model-predicted value (88.06%) with a deviation of <1.2%. This confirmed that electrode parameter optimization effectively enhanced the treatment performance of the CW-MFC system. These findings could contribute new perspectives to the performance optimization of CW-MFC systems applied to decentralized rural domestic sewage treatment, particularly under low-temperature winter scenarios.