Liangqian Fan

With the rapid development of industrialization, the amount of copper-containing wastewater is increasing, thereby posing a threat to the aquatic ecological environment and human health. Sludge biochar has received extensive concern in recent years due to its advantages of low cost and sustainability for the treatment of heavy-metal-containing wastewater. However, the heavy-metal-adsorption capacity of sludge biochar is limited. This study prepared a sodium pyrophosphate- (Na₄P₂O₇-) modified municipal sludge-based biochar (SP-SBC) and evaluated its adsorption performance for Cu(II). Results showed that SP-SBC had higher yield, ash content, pH, Na and P content, and surface roughness than original sewage sludge biochar (SBC). The Cu(II)-adsorption capacity of SP-SBC was 4.55 times than that of SBC at room temperature. For Cu(II) adsorption by SP-SBC, the kinetics and isotherms conformed to the pseudo-second-order model and the Langmuir–Freundlich model, respectively. The maximum adsorption capacity of SP-SBC was 38.49 mg·g⁻¹ at 35°C. Cu(II) adsorption by SP-SBC primarily involved ion exchange, electrostatic attraction, and precipitation. The desired adsorption performance for Cu(II) in the fixed-bed column experiment indicated that SP-SBC can be reused and had good application potential to treat copper-containing wastewater. Overall, this study provided a desirable sorbent (SP-SBC) for Cu(II) removal, as well as a new simple chemical-modification method for SBC to enhance Cu(II)-adsorption capacity.

CH₄ flux measured by a portable chamber using an infrared analyzer was compared with the flux by static chamber measurement for CW at 13 different sites from May 2012 to May 2017 in the Living Water Garden (LWG) in Chengdu, Sichuan Province, China, over 4 timescales (daily, monthly, seasonal, and annual). During the measurement period, a total of 1443 data were collected. CH₄ fluxes were measured using the portable chamber method and the results showed that the annual mean and median CH₄ flux values in the LWG were 17.4 mg m⁻² h⁻¹ and 6.2 mg m⁻² h⁻¹, respectively, ranging from − 19.7 to 98.0 mg m⁻² h⁻¹. Cumulative CH₄ emissions for LWG ranged from − 0.17 to 0.86 kg m⁻² year⁻¹. Global warming potential (GWP, 25.7 kg CO_2eq m⁻² year⁻¹) was at a high level, which means that the LWG was a source of CH₄ emissions. Significant temporal variations on the 4 timescales were observed. And the asymmetry of measurement uncertainty of CH₄ flux increases with the timescale. Although the total mean CH₄ flux measured by the portable chamber method was 42.1% lower than that of the static chamber method, the temporal variation trends of CH₄ flux were similar. The uncertainty of CH₄ flux measured in portable chamber was more symmetrical than that in static chamber. These results suggest that the portable chamber method has considerable value as a long-term measurement method for CH₄ flux temporal variations.

Pyrolysis temperature affects biochar properties, which in turn determine its application potential. Here, we examined the properties of crofton weed biochar (C-BC) produced at different pyrolysis temperatures of 300°C, 400°C, 500°C, and 600°C. We measured the yield, ash content, pH, iodine sorption value (ISV), and elemental composition of C-BC. We also characterized C-BC using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared, as well as its ability to remove Pb²⁺ and Cd²⁺ from aqueous solution. C-BC yield decreased with increasing pyrolysis temperature, whereas ash content and pH increased. ISV first increased at 300–400°C and decreased at 500–600°C. For C-BC produced at pyrolysis temperatures 300–600°C (C-BC300 to C-BC600, respectively), H, N, and O content decreased, but C, Ca, Mg, P, and K content increased with increasing temperature. Water-soluble K⁺ content had the same trend as the K content, and water-soluble Ca²⁺, Mg²⁺, PO₄³⁻, NO₃⁻, and NH₄⁺ content decreased with increasing pyrolysis temperature. The (NO₃⁻+NH₄⁺), PO₄³⁻, and K⁺ content of C-BC was high, and the K⁺ content in C-BC600 was particularly high at up to 26,293.33 mg/kg. All C-BCs had a certain number of pore structures. Increasing pyrolysis temperatures decreased the amount of -OH, -COOH, aliphatic C-H, and polar C-O on the C-BC surface. As the pyrolysis temperature increased, calcium magnesium carbonate, calcium magnesium silicate, calcium magnesium phosphate, and potassium salt crystalline minerals gradually formed. The percentage of Pb²⁺ and Cd²⁺ removed increased with increasing pyrolysis temperatures. Overall, for C-BC, a low pyrolysis temperature was beneficial for producing a more porous biochar and increased content of water-soluble calcium, magnesium, nitrogen, and phosphorus, whereas high pyrolysis temperatures yield biochar that had high alkalinity, aromaticity, and stability, as well as heavy metal removal activity and water-soluble potassium content.

This work aims to investigate the methane emissions from integrated vertical-flow constructed wetlands (IVCWs) when ethanol is added as an external carbon source. In this study, a gradient of ethanol (0, 2, 4, 8, 16 and 32 mmol/L) was added as the carbon source in an IVCW planted with Cyperus alternifolius L. The results showed that the methane emission flux at an ethanol concentration of 32 mmol/L was 32.34 g CH₄ m⁻² day⁻¹ less than that of the control experiment (0 mmol/L) and that the methane emission flux at an ethanol concentration of 16 mmol/L was 5.53 g CH₄ m⁻² day⁻¹ less than that at 0 mmol/L. In addition, variations in the water quality driven by the different ethanol concentrations were found, with a redox potential range of −64 mV to +30 mV, a pH range of 6.6–6.9, a chemical oxygen demand (COD) removal rate range of 41% to 78%, and an ammonia nitrogen removal rate range of 59% to 82% after the ethanol addition. With the average CH₄-C/TOC (%) value of 35% driven by ethanol, it will be beneficial to understand that CH₄-C/TOC can be considered an ecological indicator of anthropogenic methanogenesis from treatment wetlands when driven by carbon sources or carbon loading. It can be concluded that adding ethanol as an external carbon source can not only meet the water quality demand of the IVCW treatment system but also stimulate and increase the average CH₄ emissions from IVCWs by 23% compared with the control experiment. This finding indicates that an external carbon source can stimulate more CH₄ emissions from IVCWs and shows the importance of carbon sources during sewage treatment processes when considering greenhouse emissions from treated wetlands.

To understand the effects of effective microorganisms (EMs) containing multiple strains on microbes and nutrients in kiwifruit planting soil, EMs prepared with four different strains were added to kiwifruit planting soil monthly from April to August. The counts of bacteria, fungi, actinomycetes, and total microbes were determined. The pH, total nitrogen (TN), alkali-hydrolyzable nitrogen (A-N), organic matter (OM), available potassium (A-K), and available phosphorus (A-P) of the soil were measured. Results indicated that the counts of bacteria, fungi, actinomycetes, and total microbes reached 60.33 × 10⁵, 4.00 × 10⁵, 0.92 × 10⁵, and 65.25 × 10⁵ CFU/g, respectively, in August, all of which were higher than those of the control group (CK). The bacterial count of the experimental group (EG) was higher than that of the CK in August. The pH-values of the EG were always lower than those of the CK. In August, the TN content of the EG was 1.52 g/kg, which was higher than that of the CK (1.35 g/kg). A significant negative association between the actinomycetes count and TN (p < 0.05) was found. For A-N and OM, the content of the EG (A-N, 125.18 mg/kg; OM, 49.84 mg/kg) was roughly the same as that of the CK (A-N, 112.51 mg/kg; OM, 53.11 mg/kg) in August. However, the A-K and A-P contents of the EG (A-K, 145.25 mg/kg; A-P, 111.25 mg/kg) were lower than those of the CK (A-K, 182.52 mg/kg; A-P, 202.19 mg/kg) in August. Results show that application of EMs in kiwifruit planting soil can increase the counts of soil microbes and might promote the absorption of major nutrients for kiwifruit tree.