Metal-free graphene-based catalytic membranes for persulfate activation toward organic pollutant removal: a review.

Owing to their ultrathin two-dimensional structure and efficient catalytic ability for persulfate activation, graphene-based nanocarbons exhibit considerable application potential in fabricating carbonaceous composite membranes for in situ catalytic oxidation to remove organic pollutants. This approach offers significant advantages over conventional batch systems. However, the relationships between the physicochemical properties of carbon mats and performance of graphene-based catalytic membranes in water purification remain ambiguous. Herein, we summarize the main mechanisms of in situ catalytic oxidation and the facile fabrication strategies of carbonaceous composite membranes. Different factors influencing the performance of graphene-based catalytic membranes are comprehensively discussed. The defective level, heteroatom doping, and stacking morphology of carbon mats and operational conditions during filtration play critical roles in the oxidative degradation of target pollutants. Long-term operation leads to the deterioration of catalytic activity and transmembrane pressure, especially in the complex water matrix. Finally, the present challenges and future perspectives are presented to improve the anti-fouling performance and catalytic stability of membranes and develop scalable fabrication methods to promote the engineering applications of in situ catalytic oxidation in real water purification.

Effect of particle size on adsorption of norfloxacin and tetracycline onto suspended particulate matter in lake.

Aquatic systems are important sinks of antibiotics; however, their final destination has not been completely elucidated. Therefore, we investigated the adsorption behaviors of suspended particulate matter (SPM) in lakes to support the analysis of the migration and transformation of antibiotics in lacustrine environments. SPM was collected from Meiliang Bay (ML) and Gonghu Bay (GH) in Lake Taihu, China, which was sieved into four particle sizes of >300, 150-300, 63-150, and <63 µm for subsequent antibiotic adsorption experiments. All particles exhibited rapid and substantial adsorption of tetracycline and norfloxacin. Most size fractions fit a Langmuir model, indicative of monomolecular adsorption, except the <63-µm fraction, which fit a Freundlich model. Particle size had a substantial influence on antibiotic adsorption; the 63-150-µm fraction had the greatest adsorption capacity, while the >300-µm fraction had the lowest capacity. The influence of particle size on adsorption was mainly related to SPM physicochemical properties, such as cation exchange capacity, surface area, and organic matter content, rather than types of functional groups. Considering the mass ratios, the <63-µm fraction had the greatest contribution to adsorption. Antibiotics adsorbed onto the SPM from ML and GH exhibited different behaviors. The ML SPM settled more readily into sediment, and larger, denser particles were more resistant to resuspension. Conversely, the GH SPM was more likely to be found in the water column, and larger, less-dense particles remained in the water column. These results help improve our understanding of the interactions between SPM and antibiotics in aquatic systems.

Excessive sulfur supply reduces cadmium accumulation in brown rice (Oryza sativa L.).

Human activities have resulted in cadmium (Cd) and sulfur (S) accumulation in paddy soils in parts of southern China. A combined soil-sand pot experiment was conducted to investigate the influence of excessive S supply on iron plaque formation and Cd accumulation in rice plants, using two Cd levels (0, 1.5 mg kg(-1)) combined with three S concentrations (0, 60, 120 mg kg(-1)). The results showed that excessive S supply significantly decreased Cd accumulation in brown rice due to the decrease of Cd availability and the increase of glutathione in rice leaves. But excessive S supply obviously increased Cd accumulation in roots due to the decrease of iron plaque formation on the root surface of rice. Therefore, excessive S supply may result in loss of rice yield, but it could effectively reduce Cd accumulation in brown rice exposed to Cd contaminated soils.

Atmospheric inorganic nitrogen deposition to a typical red soil forestland in southeastern China.

A 2-year monitoring study was conducted to estimate nitrogen deposition to a typical red soil forestland in southeastern China. The dry deposition velocities (V(d)) were estimated using big leaf resistance analogy model. Atmospheric nitrogen dry deposition was estimated by combing V(d) and nitrogen compounds concentrations, and the wet deposition was calculated via rainfall and nitrogen concentrations in rainwater. The total inorganic nitrogen deposition was 83.7 kg ha(-1) a(-1) in 2004 and 81.3 kg ha(-1) a(-1) in 2005, respectively. The dry deposition contributed 78.6% to total nitrogen deposition, in which ammonia was the predominant contributor that accounted for 86.1%. Reduced nitrogen compounds were the predominant contributors, accounting for 78.3% of total nitrogen deposition. The results suggested that atmospheric inorganic nitrogen could be attributed to intensive agricultural practices such as excessive nitrogen fertilization and livestock production. Therefore, impacts of atmospheric nitrogen originated from agriculture practices on nearby forest ecosystems should be evaluated.