In this work, the chitosan/bentonite composite was favorably prepared and further used for Cr­(VI) removal from aqueous solutions via a batch adsorption process. The characteristics of the chitosan/bentonite composite were determined by using scanning electron microscopy, Brunner–Emmet–Teller measurement, Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction, and the results reveal the evidence of the interaction between functional groups of chitosan with bentonite, which is helpful for the adsorption of Cr­(VI). The adsorption performance of the chitosan/bentonite composite is better than that of chitosan or bentonite, and the effects of adsorbent dosage, shaking speed, pH, and temperature were investigated. The results indicate that the percentage removal of Cr­(VI) increases with an increase in adsorbent dosage, the external diffusion resistance is maintained constant when the shaking speed exceeds 210 rpm, and the optimum pH is 3. The isotherm and kinetic experimental data of Cr­(VI) adsorption onto the chitosan/bentonite composite were best-fitted by Redlich–Peterson and Elovich models, respectively. The adsorption process is an exothermic and of the multilayer variety. The desorption rates of Cr­(VI) can be achieved at 60.1% with 0.1 M NaOH. The analysis FT-IR of adsorbents before and after adsorption, adsorption thermodynamics and kinetics, and desorption experiment reveal that the adsorption of Cr­(VI) on the chitosan/bentonite composite is predominantly a chemical interaction. The above results suggested that the chitosan/bentonite composite can be employed as a cost-effective and environmentally friendly adsorbent for Cr­(VI) removal from wastewater.

Soil metal contamination leads to a decrease in a yield of crops and is a threat to human health. In the present study, the properties (i.e., photosynthetic pigments, gas-exchange parameters, chlorophyll fluorescence, biomass, leaf area, leaf mass per area) of three green vegetables (i.e., Brassica chinensis, Chrysanthemum coronarium, Brassica alboglabra) grown under various Cu treatments [0, 200, 400, and 600 mg(Cu) kg -1 ] were measured and analysed. The results showed that soil Cu contamination resulted in the damage of photosynthetic pigments, negative effects on gas exchange, and hampered growth of all three vegetables. However, it did not significantly influence PSII functions of the three vegetables. It indicates that soil Cu contamination negatively affected photosynthesis particularly due to stomatal factors, but not due to the damage of photosynthetic apparatus.

In a controlled experiment, we assessed the effect of phosphate-solubilizing bacterium (PSB) on the soil metal (Cu) phytoremediation by Wedelia trilobata and examined the effect of the interaction of Cu contamination and PSB on the growth of W. trilobata. We also explored the effect of the interaction of Cu contamination and PSB on the soil microflora. The results showed that the removal efficiency of Cu from soil by W. trilobata increased with an increase in the concentration of PSB, and the translocation factors of Cu (i.e., leaf:root and stem:root) were both significantly upregulated by PSB. The PSB significantly promoted the growth of W. trilobata; however, the effect of the Cu-PSB interaction on the leaf net photosynthetic rate (Pn) of W. trilobata was not significant, whereas copper contamination had a significant negative influence on the soil microflora, PSB had a significant positive influence on the soil microflora. Thus, PSB improved the phytoremediation efficiency of W. trilobata in Cu-contaminated soil because of the positive influence on the soil microflora, improving soil quality, which then increased the growth of W. trilobata in Cu-contaminated soil. The vigorous growth of W. trlobata led to higher of Cu absorption and translocation from soil as the ultimate result.

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