Wenchao Yang

Generally, marine dredged sediments often exhibit co-pollution with heavy metals and petroleum hydrocarbons. This work investigates the extraction-oxidation synergistic remediation treatment of heavy metals (Cu and Pb) and total petroleum hydrocarbon (TPH) in the contaminated dredged sediments. The leachability of heavy metals, the oxidation of TPH, the physicochemical properties of the treated sediment, and the fertility of the treated sediment for barley growth are compared among different combinations of extractants [ethylene diamine tetraacetic acid (EDTA), citric acid (CA) and ferric chloride (FeCl₃)] and oxidant [potassium persulfate (K₂S₂O₈)]. The results show that the extraction-oxidation synergistic remediation treatment significantly reduces the Cu and Pb contents. The total removal performances of heavy metals and TPH in the contaminated dredged sediments by each co-remediation treatment group are FeCl₃+Ox > EDTA-Ox > CA-Ox. Specifically, FeCl₃+Ox and EDTA-Ox achieve the highest removal rates of 91.10% and 96.95% for Cu and Pb, respectively. The extractant affects the activation of K₂S₂O₈ by transition metals, enhancing the removal efficiency of TPH. The EDTA-Ox treatment group demonstrates the optimal treatment efficiency (37.42%) for TPH in the dredged sediment in 30 min. In the barley planting experiment, both shoot and root germinations in the EDTA-Ox treatment group reach their maximum values of 100% and 90%, respectively. Additionally, the CA-Ox treatment group exhibits maximal shoot and root lengths of 11.6 cm and 12.1 cm, respectively. The stress caused by salinity on seeds is also mitigated by the treatment. This study can provide technical support for the beneficial use of the dredged sediment.

All-inorganic lead halide perovskite has emerged as an attractive semiconducting material due to its unique optoelectronic properties. However, its poor environmental stability restricts its broad application. Here, a simple method for the fabrication of CsPb₂Br₅/TiO₂ is investigated. The introduction of p-aminobenzoic acid, which has two functional groups, is critical for the capping of amorphous TiO₂ on CsPb₂Br₅. After calcination at 300 °C, amorphous TiO₂ crystallizes into the anatase phase. The CsPb₂Br₅/TiO₂ NCs show high long-term stability in water and enhanced stability against ultraviolet radiation and heat treatment, owing to the chemical stability of TiO₂. More importantly, photo-electrochemical characterizations indicate that the formation of TiO₂ shells can increase the charge separation efficiency. Hence, CsPb₂Br₅/TiO₂ exhibits improved photoelectric activity owing to the electrical conductivity of the TiO₂ in water. This study provides a new route for the fabrication of optoelectronic devices and photocatalysts based on perovskite NCs in the aqueous phase. Furthermore, the present results demonstrate that CsPb₂Br₅/TiO₂ NCs has considerable potential to be used as a photoelectric material in optical sensing and monitoring.

There are more than 150 ports in China and a considerable proportion of dredged sediments in ports and waterways are contaminated with heavy metals as the typical contaminants. It is mandatory to remediate the contaminated dredged sediments prior to further resource utilization. The over-arching objective of this study was to use natural organic acids (oxalic acid, citric acid, tartaric acid, and malic acid) as leaching agents to remove heavy metals (Cu, Cd, and Pb) from contaminated dredged sediments. Batch experiments were conducted to investigate the factors governing the removal rate of heavy metals and leaching kinetics. Citric acid had the best leaching effect on heavy metals Cu, Cd, and Pb with an optimal leaching concentration of 20 mmol/L and a solid-to-liquid ratio of 1:20. The average removal rates of Cu, Cd, and Pb were 85%, 73%, 56%, and 35% for citric acid, malic acid, tartaric acid, and oxalic acid, respectively. The leaching kinetics showed that the removal of heavy metals increased rapidly with time and then gradually reached the maximum value which was best described by the Elovich equation model. The outcomes of this study suggest that citric acid is an effective and environmentally friendly leaching agent for removing heavy metals from marine dredged sediments.

Enteromorpha biochar (BC) has been proposed as a potential absorbent in the marine environments. This study attempts to understand the process of active capping using Enteromorpha BC to prevent the release of heavy metals (Pb and Cd) from contaminated marine dredged sediments. The capping efficiency was assessed with a series of lab-scale column experiments. Results showed that the Enteromorpha BC exhibits rough pore structure and higher specific surface area, as well as more surface organic functional groups, which is favorable for its adsorption capacity and selectivity towards heavy metals. The capping thickness of 2 cm for Enteromorpha BC was sufficient to prevent the release of heavy metals from sediments, with the capping efficiency of 47% for Pb and 62% for Cd. Kinetic studies showed that heavy metals released into the overlying water can be described by a three-parameter sigmoidal kinetic model. Importantly, the fractions of heavy metals in the dredged sediments below the capping layer were analyzed to reveal the capping remediation mechanism. The outcomes of the present study indicate that capping with Enteromorpha BC is a promising method to regulate the water environment by preventing the release of heavy metals from the contaminated dredged sediments.