Junxia Wang

Phytoremediation is a promising technique for remediation of cadmium (Cd)-contaminated soils, while the derived Cd-rich phytoremediation biomass should be appropriately disposed of. In this work, anaerobic digestion was employed as a synergistic strategy to simultaneously address these challenges by converting Cd-rich Sedum alfredii biomass into biogas energy and stabilized digestate without external chemical amendments. The process maintained robust stability, achieving a methane yield of 237 mL/g VS with kinetics well described by the modified Gompertz model (R² > 0.99). Microbial community succession revealed that Chloroflexota and Pseudomonadota dominated hydrolysis and acidogenesis, while Desulfobacterota enriched in the mid-to-late phase drove Cd immobilization via sulfide precipitation, and acetoclastic Methanothrix became the dominant methanogen. Over 83% of total Cd was retained in the solid digestate, where the exchangeable fraction dropped sharply from 80% to 22%, and Cd was transformed into stable Fe-Mn oxide-bound, organic-bound, and residual forms. Leachates from both TCLP and SPLP tests were far below U.S. Environmental Protection Agency regulatory limits, and the biogas slurry met China’s fertilizer standards. This study establishes a sustainable anaerobic digestion-based strategy for the concurrent recovery of bioenergy and heavy metal stabilization from phytoremediation biomass, offering a feasible pathway toward safe resource utilization and environmental risk mitigation of phytoremediation residues.

Sewage sludge production is increasing rapidly, yet current sludge treatment capacity and technology remain insufficient. The thermochemical process has been widely adopted for sewage sludge disposal; its solid product (bio/hydro-char) shows considerable potential to improve soil quality by enriching soil nutrient contents. However, limited heavy metals are volatilized during the thermochemical process, and the majority is concentrated in the derived bio/hydro-char. Therefore, it is essential to ensure the environmental safety of sewage sludge-derived bio/hydro-char and avoid heavy metal risk, and thus appropriate heavy metal removal technology is required prior to land application. This review provides an overview of the major sewage sludge treatment approaches focusing on the heavy metal removal and phosphorus recovery, along with emerging challenges and future perspectives for the sustainable utilization of sewage sludge. Notably, the combination of electrokinetic treatment with thermochemical treatments emerges as a promising strategy to simultaneously treat sewage sludge and achieve P reclamation.

With the rapid development of industry worldwide, soil and water pollution has increased in recent decades

The objective of this study was to investigate the feasibility of using modified biochars to enhance removal of ammonium from aqueous solution. The pristine, NaOH-modified, ball-milled, and NaOH-modified ball-milled biochars were prepared from wheat straw at 500 °C. The surface morphology and characteristics of biochar were obviously changed after modification. The NaOH-modification elevated the pH value and ash content of biochar, and the ball-milling treatment promoted the formation of oxygen-containing functional groups. The specific surface area of biochar (20.9 m²/g) increased to 51.4 m²/g and 145.6 m²/g after NaOH-modification and ball-milling treatment, respectively. The modified biochars showed considerable ammonium sorption capacity in a wide pH range (3–7), and the optimal pH of ammonium sorption was around 6. Both NaOH-modification and ball-milling treatment improved ammonium sorption on the biochars. Ammonium sorption of the biochars could be well fitted by the Langmuir and pseudo-second-order model, and the NaOH-modified ball-milled biochar showed the highest ammonium sorption capacity of 8.93 mg g⁻¹. The surface complexation with oxygen-containing functional groups and cation exchange were the dominant mechanisms of ammonium sorption on the biochars. These results indicate that NaOH-modified/ball-milled biochar has a good potential to be used for the ammonium removal from polluted water.

Large amounts of sewage sludge (SS) and wetland plant wastes are generated in the wastewater treatment system worldwide. The conversion of these solid wastes into biochar through co-pyrolysis could be a promising resource utilization scheme. In this study, biochar was prepared by co-pyrolysis of SS and reed (Phragmites australis, RD) using a modified muffle furnace device under different temperatures (300, 500, and 700 °C) and with different mixing ratios (25, 50, and 75 wt.% RD). The physicochemical properties of biochar and the transformation behaviors of phosphorus (P) and heavy metals during the co-pyrolysis process were studied. Compared with single SS pyrolysis, the biochar derived from SS-RD co-pyrolysis had lower yield and ash content, higher pH, C content, and aromatic structure. The addition of RD could reduce the total P content of biochar and promote the transformation from non-apatite inorganic phosphorus (NAIP) to apatite phosphorus (AP). In addition, co-pyrolysis also reduced the content and toxicity of heavy metals in biochar. Therefore, co-pyrolysis could be a promising strategy to achieve the simultaneous treatment of SS and RD, as well as the production of value-added biochar.