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A novel g‐C3N4/MnO2 composite was prepared by in situ deposition of MnO2 on graphitic carbon nitride (g‐C3N4) nanosheets, and its adsorption properties were evaluated for removal of Pb (II) in aqueous. Fourier transform‐infrared, spectrometer scanning electron microscopy and transmission electron microscopy characterization showed the g‐C3N4/MnO2 composite had a two‐dimensional/two‐dimensional (2D/2D) structure with ample active sites. The Brunauer–Emmett–Teller specific surface area of g‐C3N4/MnO2 composites (234.9 m2/g) was 13.5 times larger than that of g‐C3N4 (17.37 m2/g), providing better conditions for adsorption. The adsorption kinetic data were better fitted with the pseudo‐second‐order model. The Langmuir model was more suitable for describing the experimental equilibrium data of g‐C3N4/MnO2, and the maximum adsorption capacity was 204.1 mg/g for Pb (II). The adsorption of g‐C3N4/MnO2 composite for Pb (II) was an endothermic and spontaneous process, and reached adsorption equilibrium rapidly within initial 150 min. This composite was an excellent adsorbent because of its higher adsorption capacity and facile preparation progress. [ABSTRACT FROM AUTHOR]

Continuous rice cultivation and excessive use of chemical fertilizers result in soil acidification and heavy metal pollution in southern China. An activated Ca Si mineral remediation material (CSRM) was innovatively prepared by two-stage modification (calcination with mixed salts and the hydrothermal activation) of primary aluminosilicate Potash feldspar. Based on the excellent results of previous pot experiments, this material was used for in situ remediation of cadmium contaminated paddy fields. Adding 4500 kg/hm2 of the material, the cadmium contents in rice and the available cadmium contents in soil was reduced significantly by 41.43%–73.32% and 16.67%–31.13%, accompanied by the increase of soil pH 0.68–0.82 and rice yield 4.24%–11.22%. To further study the remediation mechanism of cadmium, the composite was used for Cd(II) removal in aqueous solution, in combination with SEM, EDX, XPS, XRD, XRF, and BET analysis. The adsorption isothermal data was more suitable with the Langmuir model, and the kinetics can be well described by the pseudo-second-order model. The isothermal study also demonstrated an adsorption process on homogeneous surface along with monolayer adsorption and the maximum capacity obtained from the Langmuir model was 273.2 mg/g at 328 K. By instrumental analysis, it could be known that stable carbonates and silicates were formed by the interaction of materials with cadmium ions, and this process was feasible, spontaneous and endothermic. Ion exchange was found to be the most important chemical process, followed by precipitation, surface complexation and adsorption. The porosity of clay was another significant reason for the removal of heavy metals by adsorption mechanism. Unlabelled Image • The activated Ca-Si mineral remediation material can reduce the cadmium contents in rice and the available cadmium contents in soil significantly. • Cadmium ion was immobilized by ion exchange, precipitation, surface complexation and adsorption. • Ion exchange was found to be the most important chemical process. • The immobilization process of cadmium owns long-term effect and high stability. [ABSTRACT FROM AUTHOR]