The article summarizes the modification effects of different loads on nZVI, as well as the preparation methods for nZVI particles and their effects and mechanisms in commonly used antibiotic contaminated environments.

Rice husk ash is a kind of biomass material. Its main component is silicon dioxide, with a content of up to 80%. It has high pozzolanic activity and can react with hydroxide in cement. When treating rice husks, rice husk ash with high volcanic ash activity and a good microaggregate filling effect can be obtained by selecting a suitable incineration environment. These advantages make rice husk ash an ideal concrete admixture, replacing the traditional admixture such as fly ash and slag in concrete. This paper summarizes the preparation methods and physical and chemical properties of rice husk ash, as well as the physical and chemical properties of rice husk ash concrete, such as mechanical properties, temperature resistance, freezing resistance, permeability resistance and chemical erosion resistance. The results show that using 20% rice husk ash as a substitute material for cement improves the resistance strength, compressive strength, flexural strength, and permeability of concrete. In short, the incorporation of rice husk ash can effectively improve the performance of cement-based materials, which will be conducive to the green development of the building material industry and the implementation of the two-carbon strategy.

As an adsorbent, biochar has a highly porous structure and strong adsorption capacity, and can effectively purify the environment. In response to the increasingly serious problem of heavy metal pollution in water, this study used nano zero valent iron and rice husk biochar to prepare a new type of magnetic sheet-like biochar loaded nano zero valent iron (BC-nZVI) composite material through rheological phase reaction, showing remarkable advantages such as low cost, easy preparation, and superior environmental remediation effect. The physical and chemical properties and structure of the material were extensively characterized using various methods such as HRTEM, XPS, FESEM, EDS, XRD, FTIR, and RAMAN. Concurrently, batch experiments were undertaken to assess the removal efficiency of Pb(II) by BC-nZVI, with investigations into the influence of pH value, temperature, soil water ratio, and initial concentration of heavy metal ion solution on its removal efficiency. The results indicate that the removal of Pb(II) by BC-nZVI reaches an equilibrium state after around 120 minutes. Under the conditions of pH 6, temperature 20 °C, soil water ratio 1 : 5, and BC-nZVI dosage of 1 g L⁻¹, BC-nZVI can reduce the Pb(II) content in wastewater with an initial concentration of 30 mg L⁻¹ to trace levels, and the treatment time is about 120 minutes. The analysis of adsorption kinetics and isotherms indicates that the adsorption process of Pb(II) by BC-nZVI adheres to the quasi-second-order kinetic model and Langmuir model, suggesting a chemical adsorption process. Thermodynamic findings reveal that the adsorption of Pb(II) by BC-nZVI is spontaneous. Furthermore, BC-nZVI primarily accumulates Pb(II) through adsorption co-precipitation. BC-nZVI serves as an eco-friendly, cost-effective, and highly efficient adsorbent, showing promising capabilities in mitigating Pb(II) heavy metal pollution. Its recoverability and reusability facilitated by an external magnetic field make it advantageous for remediating and treating lead-contaminated sites.

Nanoscale zero-valent iron (nZVI) and its composites are known for their excellent ability to remove Cr(VI), but their preparation can be expensive due to the reduction processes. This study presents a cost-effective method to prepare core@shell structured nZVI@Fe₃O₄ nanocomposites using a novel Fe(II) disproportionation reaction. The nZVI@Fe₃O₄ was thoroughly characterized using various techniques, including FESEM, HRTEM, EDS, XPS, XRD, FTIR, and VSM. Batch experiments were performed to evaluate the removal efficiency of nZVI@Fe₃O₄ in eliminating Cr(VI) ions from aqueous solutions, while classical models were employed to investigate the influencing factors associated with the removal process. The results showed that a 0.7 mg per ml NaOH solution reacted with Fe(II) at 150 °C for 0.5 h could be used to prepare nZVI@Fe₃O₄ composites efficiently and inexpensively. nZVI@Fe₃O₄ was able to remove more than 99% of Cr(VI) from both simulated Cr(VI) solutions and real electroplating wastewater, and the recovery and preparation could be easily performed using external magnets to separate it from the solution. At pH 6.0, the maximum adsorption capacity (q_max) for Cr(VI) reached 58.67 mg g⁻¹. The reaction mechanism was discussed from the perspective of electron transfer. Overall, the results suggest that nZVI@Fe₃O₄, an efficient adsorbent prepared using an environmentally friendly and inexpensive Fe(II) disproportionation reaction, is a promising option for the treatment of Cr(VI) from industrial wastewater and other contaminated water sources.

In this study, we prepared a low-cost novel Cu/Cu₂O/BC nanocomposite visible-light photocatalyst by the impregnation method using CuSO₄·5H₂O and rice husk biochar (BC) as raw materials and Na₂S₂O₄ as a single reductant to improve the stability and dispersion of the Cu/Cu₂O nanoparticles, in order to solve their aggregation tendency during photocatalysis. The morphology and structure of the Cu/Cu₂O/BC were characterized using various analytical and spectroscopic techniques. The photocatalytic effect and cyclic stability of the synthesized photocatalyst on methyl orange (MO) removal were investigated under visible light radiation and various parameter conditions, including the mass ratio of BC to Cu/Cu₂O, initial MO concentration, pH, temperature, and catalyst dosage. The results show that the synthesized Cu/Cu₂O/BC nanocomposite composed of Cu/Cu₂O spherical particles was loaded on the BC carrier, which has better stability and dispersion. The best adsorption–photocatalytic effect of the Cu/Cu₂O/BC is exhibited when the mass ratio of BC to Cu/Cu₂O is 0.2. A total of 100 mg of Cu/Cu₂O/BC can remove 95% of the MO and 88.26% of the COD in the aqueous solution at pH = 6, T = 25 °C, and an initial MO concentration of 100 mg/L. After five cycles of degradation, the MO degradation rate in the sample can still remain at 78.41%. Both the quasi-secondary kinetic model and the Langmuir isothermal adsorption model describe the adsorption process. Additionally, the thermodynamic analysis demonstrates that the photocatalytic process follows the quasi-primary kinetic model and that the removal process is of spontaneous heat absorption. The photocatalyst described in this paper offers a cost-effective, easily prepared, and visible-light-responsive solution for water pollution treatment.