Magnetic core–shell Fe₃O₄@SiO₂ nanoparticles were synthesized by sol–gel method. Based on the characterization and experimental results, the adsorbent was found to have an average particle size of approximately 120 nm, a pore size range of 2–5 nm and superparamagnetic properties. It exhibited electrostatic and hydrogen bonding interactions during adsorption of methyl orange (MO). The adsorption of MO on the magnetic Fe₃O₄@SiO₂ nanoparticles exhibited pseudo-second-order kinetics, the adsorption process is a spontaneous endothermic adsorption process, which conforms to the Langmuir adsorption isotherm model. he maximum amount of MO was adsorbed at pH = 2, T = 45 °C and t = 30 min, and the highest adsorption capacity was 182.503 mg/g; The unit adsorption capacity of the Fe₃O₄@SiO₂ nanoparticles still reached 83% of the original capacity after 5 cycles, so the material was reusable and met the requirements of environmental protection. This study reveals the great potential of magnetic mesoporous nanoparticles for removal of dyes from wastewater.

Since ferric tetroxide (Fe₃O₄) has strong magnetic properties, coating amorphous silica (SiO₂) with Fe₃O₄ nanoparticles can protect the magnetic Fe₃O₄ particles and form a new magnetic adsorbent with a core–shell structure and small pore size, the strong magnetic properties of which can efficiently solve the problem of the difficult separation and recovery of heavy metals from wastewater affecting present-day adsorption techniques. In this paper, SiO₂-coated nanoscale Fe₃O₄ particles were prepared using a modified sol–gel method for the adsorption and removal of Cr(VI) at lower pollution concentrations. The adsorbent was characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and a magnetic vibration sample magnetometer (VSM), and its adsorption performance was systematically investigated in terms of initial concentration, pH, and temperature. The experiments showed that the adsorption effect was optimal when the initial solution Cr(VI) was 40 mg/L. The adsorption capacity increased with a decrease in the initial solution’s pH and decreased with an increase in temperature. Furthermore, the adsorption capacity of Cr(VI) at low concentrations was much higher than that of other conventional adsorbents, the calculated unit adsorption capacity reached 13.609 mg·g⁻¹, and the removal rate reached 64.8%. In addition, the strong magnetic nanocomposite (MS) had excellent recoverability, could achieve desorption via alkaline washing, and retained about 75% of the initial adsorption capacity after six cycles.

The synergistic regulation of the water–energy–food nexus in irrigation districts is important for promoting the sustainable management of agricultural resources in irrigation districts. In this paper, a new integrated optimization–evaluation modelling framework for the water–energy–food nexus in agricultural irrigation areas is developed. It can measure the synergistic effects of economic, social and environmental multidimensional objectives on the sustainable management of agricultural resources in irrigation areas. The model couples an optimisation module and an evaluation module, combines a multiobjective nonlinear planning model with an opportunity-constrained planning model and uses an entropy-weighted TOPSIS assessment approach to sustainably assess the multidimensional indicators of the water–energy–food nexus in irrigation districts, with full consideration given to the effects of uncertainty in agricultural water and soil resources and social systems. The feasibility of the constructed model is verified through a study of the Jinxi irrigation district. The results show that compared to the actual area, the optimised surface water and groundwater availability increased by 23.5% and 22.7%; the optimised total area increased by 4%, whereas corn decreased by 40%, rice increased by 34.6% and soybean decreased by 33.8%; the energy consumption decreased by 17.6% and the total recycled resources amounted to 8.97 × 10⁹ kg, with a combined net economic benefit of CNY 1.25 × 10⁹ more than the actual current amount. The synergistic development of the water–energy–food nexus (WEFN) in the district is relatively harmonious, suggesting that the district should focus on developing agricultural mechanisation and balancing economic benefits with environmental and ecological protection; furthermore, the model constructed should provide decision-making support for the efficient use of agricultural resources in the irrigation district.

In this study, we modify the Mobil Composition of Matter No. 48 (MCM-48) silica material (MCM-48-SH) using Mercapto. The preparation conditions of MCM-48-SH are then explored, its structural characteristics are analyzed using characterization, and it is used to adsorb Cr(VI) from wastewater. A series of experiments are then designed to adsorb Cr(VI) in experimental water, and the influence of solution environment changes (such as time, temperature, pH, and coexisting ions) on the adsorption effect was explored. The experimental data showed that the MCM-48-SH material not only retained the basic structure of MCM-48 but also successfully grafted the functional group -SH. The adsorption of Cr(VI) on MCM-48-SH followed the Langmuir isotherm model and the kinetic adsorption was fitted with a pseudo-second-order kinetic model. Under these conditions, the adsorption capacity of MCM-48-SH (17.9 mg/g) on Cr(VI) was much larger than that of unmodified MCM-48 (4.0 mg/g) and amino-modified MCM-48-NH₂ (0.5 mg/g). The adsorption effect was the most obvious when the pH = 2 but the adsorption effect was not good under alkaline conditions. Other competitive ions in the solution had an influence on the adsorption effect, among which anions had a great influence. Within 3 d, when the concentration of Cr(VI) was 80 mg/L, the maximum adsorption capacity reached 17.9 mg/g and the maximum removal rate reached 93.45%. In the comparative adsorption experiment, the adsorption effect of MCM-48-SH (17.9 mg/g) on Cr(VI) was notably better than that of the other two common adsorbents: coconut shell activated carbon (9.2 mg/g) and bentonite (1.2 mg/g). In summary, MCM-48-SH can be used to effectively eliminate Cr(VI) in waste water.