Bozhi Ren

Three-dimensional electro-Fenton oxidation of N-heterocyclic compounds with a novel catalytic particle electrode: high activity, wide pH range and catalytic mechanism

A novel three-dimensional (3D) heterogeneous electro-Fenton (EF) system with sludge deserved activated carbon from sewage and iron sludge (SAC-Fe) as catalytic particle electrodes (CPEs) was constructed in this study. Its application in degrading nitrogen-heterocyclic compounds (NHCs) exhibited high catalytic efficiency over a wide applicable pH range from 3.0 to 9.0. SAC-Fe worked as both CPEs and a heterogeneous catalyst in this 3D EF system, enhancing oxidation activity. Degradation pathways of the NHCs (indole, quinoline and pyridine) and reasonable reaction mechanisms involved in this 3D EF were proposed. At pH 3.0, hydroxyl radicals were the dominant participant oxidants, following a Haber–Weiss mechanism. The FeII sites catalyzed the decomposition of electro-generated H2O2 to yield ˙OH. At pH 9.0, the oxidants generated from the decomposition of H2O2 were mainly ˙O2−/HO2˙ and to lesser extent were ˙OH. The formation and decomposition of H2O2 complex with catalytic sites (FeII and FeIII) as well as the catalytic decomposition of H2O2 were involved in the catalytic reactions to generate ˙O2−/HO2˙ and ˙OH. A quantitative structure–activity relationship analysis (QSAR) model was developed to describe the relationship between degradation properties of NHCs and their structures by involving quantum descriptors.

Treatment of antimony mine drainage: challenges and opportunities with special emphasis on mineral adsorption and sulfate reducing bacteria

The present article summarizes antimony mine distribution, antimony mine drainage generation and environmental impacts, and critically analyses the remediation approach with special emphasis on iron oxidizing bacteria and sulfate reducing bacteria. Most recent research focuses on readily available low-cost adsorbents, such as minerals, wastes, and biosorbents. It is found that iron oxides prepared by chemical methods present superior adsorption ability for Sb(III) and Sb(V). However, this process is more costly and iron oxide activity can be inhibited by plenty of sulfate in antimony mine drainage. In the presence of sulfate reducing bacteria, sulfate can be reduced to sulfide and form Sb(2)S(3) precipitates. However, dissolved oxygen and lack of nutrient source in antimony mine drainage inhibit sulfate reducing bacteria activity. Biogenetic iron oxide minerals from iron corrosion by iron-oxidizing bacteria may prove promising for antimony adsorption, while the micro-environment generated from iron corrosion by iron oxidizing bacteria may provide better growth conditions for symbiotic sulfate reducing bacteria. Finally, based on biogenetic iron oxide adsorption and sulfate reducing bacteria followed by precipitation, the paper suggests an alternative treatment for antimony mine drainage that deserves exploration.

Simultaneous Adsorption and Degradation of Cr(VI) and Cd(II) Ions from Aqueous Solution by Silica-Coated Fe0 Nanoparticles

Core-shell silica-coated Fe0 nanoparticles (Fe@SiO2) were prepared in one-step synthesis by aqueous reduction combined with modified Stöber method. The as-prepared Fe@SiO2 were then used for simultaneous removal of Cr(VI) and Cd(II) from aqueous solution. Batch tests indicated that Fe@SiO2 exhibited high removal capacity toward Cr(VI) and Cd(II). Cr(VI) was removed by Fe@SiO2 through reduction rather than adsorption, while Cd(II) removal was mainly through adsorption. The removal rate increased with increasing initial Fe NPs dose and decreased with increasing initial Cr(VI) and Cd(II) concentrations. Cd(II) adsorption was also strengthened by Cr(VI) reduction with the release of OH−. The removals of Cr(VI) and Cd(II) were weakened in the presence of cations or humic acid, as a result of aggregation and less active site of Fe@SiO2. Overall, the simply prepared Fe@SiO2 were potential material for the heavy metals removed from water.

Research on the Characteristics and Mechanism of the Cumulative Release of Antimony from an Antimony Smelting Slag Stacking Area under Rainfall Leaching

We aimed to study the characteristics and the mechanism of the cumulative release of antimony at an antimony smelting slag stacking area in southern China. A series of dynamic and static leaching experiments to simulate the effects of rainfall were carried out. The results showed that the release of antimony from smelting slag increased with a decrease in the solid-liquid ratio, and the maximum accumulated release was found to be 42.13 mg Sb/kg waste and 34.26 mg Sb/kg waste with a solid/liquid ratio of 1 : 20; the maximum amount of antimony was released within 149–420 μm size fraction with 7.09 mg/L of the cumulative leaching. Also, the antimony release was the greatest and most rapid at pH 7.0 with the minimum release found at pH 4.0. With an increase in rainfall duration, the antimony release increased. The influence of variation in rainfall intensity on the release of antimony from smelting slag was small.

Preparation and characterization of iron-copper binary oxide and its effective removal of antimony (III) from aqueous solution

An Fe-Cu binary oxide was fabricated through a simple co-precipitation process, and was used to remove Sb(III) from aqueous solution. X-ray diffraction, scanning electron microscopy, energy dispersive X-ray and N2 adsorption-desorption measurements demonstrated that the Fe-Cu binary oxide consisted of poorly ordered ferrihydrite and CuO, and its specific surface area was higher than both iron oxide and copper oxide. A comparative test indicated that Fe/Cu molar ratio of prepared binary oxide greatly influenced Sb(III) removal and the optimum Fe/Cu molar ratio was about 3/1. Moreover, a maximum adsorption capacity of 209.23 mg Sb(III)/g Fe-Cu binary oxide at pH 5.0 was obtained. The removal of Sb(III) by Fe-Cu binary oxide followed the Freundlich adsorption isotherm and the pseudo-second-order kinetics in the batch study. The removal of Sb(III) was not sensitive to solution pH. In addition, the release of Fe and Cu ions to water was very low when the pH was greater than 6.0. X-ray photoelectron spectroscopy analysis confirmed that the Sb(III) adsorbed on the surface was not oxidized to Sb(V).

Spatial Variability and Distribution of the Metals in Surface Runoff in a Nonferrous Metal Mine

The spatial variation and distribution features of the metals tested in the surface runoff in Xikuangshan Bao Daxing miming area were analyzed by combining statistical methods with a geographic information system (GIS). The results showed that the maximum concentrations of those five kinds of the metals (Sb, Zn, Cu, Pb, and Cd) in the surface runoff of the antimony mining area were lower than the standard value except the concentration of metal Ni. Their concentrations were 497.1, 2.0, 1.8, 22.2, and 22.1 times larger than the standard value, respectively. This metal pollution was mainly concentrated in local areas, which were seriously polluted. The variation coefficient of Sb, Zn, Cu, Ni, Pb, and Cd was between 0.4 to 0.6, wherein the Sbs spatial variability coefficient is 50.56%, indicating a strong variability. Variation coefficients of the rest of metals were less than 50%, suggesting a moderate variability. The spatial structure analysis showed that the squared correlation coefficient (R 2) of the models fitting for Sb, Zn, Cu, Ni, Pb, and Cd was between 0.721 and 0.976; the ratio of the nugget value (C 0) to the abutment value (C + C 0) was between 0.0767 and 0.559; the semivariogram of Sb, Zn, Ni, and Pb was in agreement with a spherical model, while semivariogram of Cu and Cd was in agreement with Gaussian model, and both had a strong spatial correlation. The trend and spatial distribution indicated that those pollution distributions resulting from Ni, Pb, and Cd are similar, mainly concentrated in both ends of north and south in eastern part. The main reasons for the pollution were attributed to the residents living, transportation, and industrial activities; the Sb distribution was concentrated mainly in the central part, of which the pollution was assigned to the mining and the industrial activity; the pollution distributions of Zn and Cu were similar, mainly concentrated in both ends of north and south as well as in west; the sources of the metals were widely distributed.

Removal of Antimony (V) from Aqueous Solution by Iron-based Adsorbents

Antimony pollution has attracted increasing attention for its toxicity. In this study, iron oxide, copper oxide and Fe-Cu binary oxide were synthesized by chemical precipitation/co-precipitation method and investigated using XRD, SEM and FTIR characterizations. Then Sb(V) removal from water by different adsorbents was evaluated. Moreover, the effect of solution pH and initial adsorbents dose was systematically investigated. It was found that removal capacity of kaolinite, aluminum oxide and MWCNTs was poor. However, Sb(V) adsorption on iron oxide and copper oxide was rapid and followed a pseudo-second-order rate law. The equilibrium adsorption capacity increased with the increasing of adsorbent dosage. Especially, when pH <5.0, the removal percentage of Sb(V) by iron oxide sharply increased. Sb(V) uptake by Fe-Cu binary oxide was better than both iron oxide and copper oxide. FTIR analysis confirmed the presence of active -OH and dynamic analysis indicated that chemical adsorption was dominant mechanism for Sb(V) adsorption. Above all, the production process of iron-based adsorbents was simple and they possessed high adsorption ability for Sb(V), Therefore, iron oxide and Fe-Cu binary oxide were promising adsorbents for antimony removal from contaminated water. Original Research Article Li et al.; ACSJ, 14(2): 1-12, 2016; Article no.ACSJ.25366 2

Removal of Mn (II) by Sodium Alginate/Graphene Oxide Composite Double-Network Hydrogel Beads from Aqueous Solutions

After the successful preparation of empirical double network hydrogel beads from graphene oxide/sodium alginate(GO/SA), its cationic metal adsorption performance in aqueous solutions were investigated. Taking Mn(II) as an example, the contribution of several factors including pH, bead dosage, temperature, contact time and initial concentration ions to adsorption efficiency were examined. The Transmission Electron Microscopy (TEM) results indicate that the GO/SA double (GAD) network hydrogel bead strongly interpenetrate and the adsorption of Mn(II) is mainly influenced by solution pH, bead dose and temperature. The GAD beads exhibit an excellent adsorption capacity of 56.49 mg g−1. The adsorption process fit both Pseudo-second order kinetic model (R2 > 0.97) and the Freundlich adsorption isotherm (R2 > 0.99) and is spontaneous. After seven rounds of adsorption-desorption cycle, the adsorption capacity of GAD hydrogel remained unchanged at 18.11 mg/g.

Recycling of Waste Sludge: Preparation and Application of Sludge-Based Activated Carbon

With the rapidly increasing industrial and agricultural development, a large amount of sludge has been produced from much water treatment. Sludge treatment has become one of the most important environmental issues. Resource utilization of sludge is one of the important efficient methods for solving this issue. Sludge-based activated carbon (SBAC) materials have high adsorption performance and can effectively remove environmental pollutants including typical organic matter and heavy metals through physical and chemical processes. Therefore, developing efficient SBAC materials is important and valuable. At present, preparation, modification, and application of SBAC materials have gained widespread attention. This paper provides a review of the research on SBAC preparation and modification and its utilization in removing environmental pollutants. It included the following topics present in this review: conventional and new methods for preparation of SBAC were clearly present; the effective methods for improving SBAC performance via physical and chemical modification were reviewed; and the correlation of their physic-chemical properties of SBAC with pollutants’ removal efficiencies as well as the removal mechanisms was revealed. SBAC has a better adsorption performance than commercial activated carbon in some aspects. Furthermore, it is a cost-effective technique and has a wide range of raw materials. However, there are still some drawbacks to its research; thus, some suggestions for further research were given in this review.

Sepiolite-Based Adsorbents for the Removal of Potentially Toxic Elements from Water: A Strategic Review for the Case of Environmental Contamination in Hunan, China

The last few decades have seen rapid industrialization and urban development in many regions globally; with associated pollution by potentially toxic elements; which have become a threat to human health and the food chain. This is particularly prevalent in a number of regions in China that host multiple mineral resources and are important agricultural locations. Solutions to protect contamination of the food chain are more effective and sustainable if locally sourced materials are available; and in this context; we review the potential of local (sepiolite) mineral deposits to treat water contamination in the Hunan Municipality; central south China; widely recognized for significant environmental pollution issues (particularly by Hg; Cd; Pb; and Cr) and the high agricultural productivity of the region. Sepiolite is an abundant fibrous clay mineral with modest to good adsorption properties and extensive industrial process applications. It shows reasonable performance as an adsorbent for element removal. In addition; a number of surface modification strategies are available that improve this capability. We review these studies; focused on sorption reaction mechanisms and regeneration potential; with a view to present options for a localized and effective economic strategy for future application.