Yidong Zou

Environmental Remediation and Application of Nanoscale Zero-Valent Iron and Its Composites for the Removal of Heavy Metal Ions: A Review.

The presence of heavy metals in the industrial effluents has recently been a challenging issue for human health. Efficient removal of heavy metal ions from environment is one of the most important issues from biological and environmental point of view, and many studies have been devoted to investigate the environmental behavior of nanoscale zerovalent iron (NZVI) for the removal of toxic heavy metal ions, present both in the surface and underground wastewater. The aim of this review is to show the excellent removal capacity and environmental remediation of NZVI-based materials for various heavy metal ions. A new look on NZVI-based materials (e.g., modified or matrix-supported NZVI materials) and possible interaction mechanism (e.g., adsorption, reduction and oxidation) and the latest environmental application. The effects of various environmental conditions (e.g., pH, temperature, coexisting oxy-anions and cations) and potential problems for the removal of heavy metal ions on NZVI-based materials with the DFT theoretical calculations and EXAFS technology are discussed. Research shows that NZVI-based materials have satisfactory removal capacities for heavy metal ions and play an important role in the environmental pollution cleanup. Possible improvement of NZVI-based materials and potential areas for future applications in environment remediation are also proposed.

Coagulation Behavior of Graphene Oxide on Nanocrystallined Mg/Al Layered Double Hydroxides: Batch Experimental and Theoretical Calculation Study

Graphene oxide (GO) has attracted considerable attention because of its remarkable enhanced adsorption and multifunctional properties. However, the toxic properties of GO nanosheets released into the environment could lead to the instability of biological system. In aqueous phase, GO may interact with fine mineral particles, such as chloridion intercalated nanocrystallined Mg/Al layered double hydroxides (LDH-Cl) and nanocrystallined Mg/Al LDHs (LDH-CO3), which are considered as coagulant molecules for the coagulation and removal of GO from aqueous solutions. Herein the coagulation of GO on LDHs were studied as a function of solution pH, ionic strength, contact time, temperature and coagulant concentration. The presence of LDH-Cl and LDH-CO3 improved the coagulation of GO in solution efficiently, which was mainly attributed to the surface oxygen-containing functional groups of LDH-Cl and LDH-CO3 occupying the binding sites of GO. The coagulation of GO by LDH-Cl and LDH-CO3 was strongly dependent on pH and ionic strength. Results of theoretical DFT calculations indicated that the coagulation of GO on LDHs was energetically favored by electrostatic interactions and hydrogen bonds, which was further evidenced by FTIR and XPS analysis. By integrating the experimental results, it was clear that LDH-Cl could be potentially used as a cost-effective coagulant for the elimination of GO from aqueous solutions, which could efficiently decrease the potential toxicity of GO in the natural environment.

β-Cyclodextrin modified graphitic carbon nitride for the removal of pollutants from aqueous solution: experimental and theoretical calculation study

A novel β-cyclodextrin modified, multifunctional, layer-by-layer graphitic carbon nitride (g-C3N4/β-CD) was successfully synthesized and applied as an effective adsorbent for the removal of methyl orange (MO) and Pb(II) from aqueous solutions under various environmental conditions (e.g., solution pH, solid content, contact time and temperature). The kinetic results indicated that the adsorption was dominated by chemisorption, and the higher adsorption capacity of g-C3N4/β-CD was attributed to it having more oxygen-containing functional groups than g-C3N4. The Langmuir, Freundlich and Sips models were applied to simulate the adsorption isotherms of MO and Pb(II), and the results demonstrated that the adsorption of MO was attributed to multilayer adsorption, while the coverage adsorption of Pb(II) on the g-C3N4/β-CD was monolayer adsorption. The thermodynamic parameters showed that the adsorption of both MO and Pb(II) was spontaneous and endothermic. The DFT calculations further evidenced the surface complexation and electrostatic interaction of Pb(II) on the g-C3N4 and g-C3N4/β-CD, whereas, the interaction of MO with g-C3N4 and g-C3N4/β-CD was mainly attributed to hydrogen bonds and strong π–π interactions. The results demonstrated that g-C3N4/β-CD is a promising material for the efficient removal of organic and inorganic pollutants in environmental pollution remediation.

Immobilization of As(V) in Rhizopus oryzae Investigated by Batch and XAFS Techniques

Arsenic (As) contamination in aqueous solutions has become an increasing public concern due to the immense harm to human health. Herein, bioaccumulation of arsenate (As(V)) by Rhizopus oryzae in aqueous systems was investigated under different environmental conditions, such as different pH’s, ionic strengths, mycelia dosages, mycelia growths, and temperatures. The results showed that As(V) could be bioaccumulated efficiently by R. oryzae, and the maximum bioaccumulation capacity of As(V) in R. oryzae was 52.4 mg/g at T = 299 K, which was much higher than that for other biomaterials under similar conditions. R. oryzae generated a higher content of thiol compounds under As(V) stress to immobilize As(V) from aqueous solutions. X-ray absorption near-edge spectroscopy analysis indicated that As(V) was partly reduced to As(III) with increasing contact time, which increased As(V) bioaccumulation in mycelia. In addition, extended X-ray absorption fine structure analysis showed that the As–S complex played an important role in As(V) immobilization by mycelia. This study provided an in-depth investigation of intracellular As speciation and coordination in R. oryzae on the molecular scale, which was crucial to understand the interaction mechanisms of As(V) with fungi during environmental cleanup.