Human activities such as mining, metal smelting, and chemical production have imported a large amount of heavy metals into the soil, which leads to a decline in soil quality and functional degradation. Soil heavy metal pollution remediation has become one of the important research hotspots at present. However, affected by a variety of factors such as pollution level, pollution range, and repair cost, there are still some shortcomings in the practical application of various repair technologies. This paper summarizes the research trends of existing soil heavy metal remediation technologies of remediation mechanism, advantages and disadvantages, and application status, and expounds on the development prospects of different technologies. The advantages of physical remediation of cycle time and efficiency hardly compensate for the disadvantages of its application of cost and damage to the soil. The lasting passivation of heavy metals by chemical stabilization needs long-term monitoring. The application scenarios and strengthening measures for bioremediation still need to be improved. Meanwhile, this study indicates that the combination of different remediation technologies can significantly improve the remediation efficiency of heavy metal-contaminated soil and reduce energy consumption, which has better development potential and application prospects. In addition, this study puts forward the prospect of the research direction of heavy metal remediation technology, intending to provide some theoretical basis for soil pollution control and prevention.

Developing adsorbent materials with higher performance for tetracycline (TC) organic pollutants in wastewater is still accounted for a hot topic in environmental remediation. As an agricultural waste, walnut green husk is often piled up in the field at will, which not only seriously affects the surrounding ecological environment, but also overlooks its potential value for practical application. Therefore, three types composite adsorbents of HA-HF300, HA-HF500 and HA-HF700 were fabricated by loading humic acid onto walnut green husk biochar (HF) prepared under different pyrolysis temperature, so as to investigate their performance for TC adsorption. The experiment results showed that HA-HF700 exhibited the highest adsorption performance for TC. The characterization results confirmed that HA-HF700 combined the advantages of both materials, and more surface functional groups and aromaticity were observed, which improved the adsorption performance of fabricated materials. In addition, HA-HF700 obtained the strongest performance for TC at solution pH of 3 with dosage of 1 g·L^-1, as the tested adsorption capacity reaching 76.20 mg·g^-1. Nonetheless, the adsorption process of HA-HF700 for TC would be inhibited when co-existing with Mg²⁺, Ca²⁺, Na⁺ and K⁺. The Pseudo-second-kinetic and Langmuir isotherm model descripted the adsorption process of HA-HF700 for TC more accurately. By integrating the results of characterization, it is believed that the adsorption mechanisms of HA-HF700 for TC mainly include electrostatic interaction, hydrogen bonding, π-π EDA interaction, and hydrophobic interaction. To conclude, this study offered a new adsorbent for tetracycline contaminated wastewater treatment.

The rapid development of camellia oleifera industry has led to a large number of camellia oleifera seed residue, which caused serious waste of resources, restricting the sustainable development of China's camellia oleifera industry. Considering the high contents of organic matter, using camellia oleifera seed residue to prepare organic fertilizer is an effective way for resource utilization. In the process of composting, cellulose, lignin and tea saponin and other biological macromolecules should be effectively biodegraded by microorganisms. In this paper, three highly efficient degrading strains targeting cellulose and lignin in camellia oleifera seed residue were obtained by screening and domestication, including 1 strain of fungus X1-1 (Pleurostomarichardsiae), and 2 strains of bacteria M4-2 (Pseudomonas monteilii) and M5-2 (Paenibacillus sp.). The three strains can also effectively reduce the content of tea saponin in fermentation products, to realize the harmless treatment of camellia oleifera seed residue. The experimental results showed that after 28 days of fermentation with strain X1-1, M4-2 and M5-2, the degradation rates of cellulose content in camellia oleifera seed residue were 29.74%, 19.65% and 13.19%, the degradation rates of lignin content were 12.84%, 17.85% and 26.39%, and the degradation rates of tea saponin content were 34.06%, 45.05% and 46.15%, respectively. Moreover, the maturity, organic matter content, andnutrient content in fermentation product of camellia oleifera seed residue all met the organic fertilizer standards. The results of this study expand the resource utilization path of camellia oleifera seed residue, and provide good strain resources for the efficient degradation of lignin and cellulose.