Ball milling of mackinawite and oxalic acid to fabricate an efficient and stable reductive material for remediation of Cr(Ⅵ)-contaminated soil.

Research on the dynamic process of NO heterogeneous and homogeneous reduction with cement raw meal in vertical tubular reactor

Pot experiments were carried out to study the effects of intercropping by Chenopodium ambrosioides L. and maize on the root exudates of soluble sugar and amino acids, in order to understand the relationship between root exudates and cadmium accumulation in plants. The results showed that, compared with monoculture system: (1) after intercropping with maize, the content of soluble sugar in root exudates of C. ambrosioides increased by 106.54%, the content of amino acids increased by 52.73%, the available Cd content in rhizosphere soil increased by 12.09%, the root Cd content increased by 15.52%. (2) The content of soluble sugar in root exudates of maize increased by 40.41%, the content of amino acids increased by 70.59%, the available Cd content in rhizosphere soil increased by 29.35%, the shoot Cd content of maize increased by 208.26%. (3) There were significantly posotive correlations between the contents of soluble sugar and amino acids secreted by C. ambrosioides and maize roots and the available Cd content in soil. In addition, there was a significant positive correlation between the available Cd content in soil and the Cd contents in the shoots and roots of plants. The results showed that the increase of soluble sugar and amino acid content of root exudates under the intercropping system caused the change of the available Cd content in the rhizosphere soil, which eventually changed the accumulation of Cd in the shoot and root of C. ambrosioides and maize.

Reduction of chromate from electroplating wastewater from pH 1 to 2 using fluidized zero valent iron process

Biogenic sulfidation of zero-valent iron (ZVI) using sulfate reducing bacteria (SRB) has shown enhanced dechlorination rates comparable to those produced by chemical sulfidation. However, controlling and sustaining biogenic sulfidation to enhance in situ dechlorination are poorly understood. Detailed interactions between SRB and ZVI were examined for 4 months in column experiments under enhanced biogenic sulfidation conditions. SRB proliferation and changes in ZVI surface properties were characterized along the flow paths. The results show that ZVI can stimulate SRB activity by removing excessive free sulfide (S2-), in addition to lowering reduction potential. ZVI also hinders downgradient movement of SRB via electrostatic repulsion, restricting SRB presence near the upgradient interface. Dissolved organic carbon (e.g., >2.2 mM) was essential for intense biogenic sulfidation in ZVI columns. The presence of SRB in the upgradient zone appeared to promote the formation of iron polysulfides. Biogenic FeSx deposition increased the S content on ZVI surfaces ∼3-fold, corresponding to 3-fold and 2-fold improvements in the trichloroethylene degradation rate and electron efficiency in batch tests. Elucidation of SRB and ZVI interactions enhances sustained sulfidation in ZVI permeable reactive barrier.

Continuous-flow columns packed with zero-valent iron and iron sulfide as a feasible strategy to remediate the persistent contaminant nitroguanidine

This study aimed to investigate the effects of zerovalent iron (ZVI/Fe0) on growth, yield and grain quality of rice (Oryza sativa L.) cv. BRRI dhan49 in arsenic (As)-contaminated soils. The pot experiment was arranged in a complete randomized design (CRD). The treatments on rice applied were As in soils at As0 (0 mg kg−1), As20 (20 mg kg−1), and As40 (40 mg kg−1) with a combination of ZVI at ZVI0 (0%), ZVI0.5 (0.5%), ZVI1.0 (1.0%), and ZVI1.5 (1.5%) with three replications. Contents of phosphorus (P), potassium (K), manganese (Mn), zinc (Zn), iron (Fe), and As in grains of rice; and Fe and As content in cultivated soils were determined. The application of ZVI had negative or no effect on shoot weight, tiller number, and grain yield. Although application of ZVI had little or no effect on thousand grain weight, P, K, Zn, and Mn of rice grains, Fe content in rice grains was increased by ZVI treatments in a dose-dependent manner. The grain As content was non-significantly reduced by the ZVI application. Soil bacterial population was negatively influenced by the ZVI in a dose-dependent manner which might be linked with As content in the soils. Therefore, a further elaborative study is needed to elucidate the mechanisms of the effects of ZVI and soil As on rice and rhizosphere soil microorganisms.

The roles of pyrite for enhancing reductive removal of nitrobenzene by zero-valent iron

We investigated the horizontal migration and transformation of nitrogen in soil with oxalic acid and inhibitors (e.g., nitrification inhibitors, DMPP, urease inhibitors, and NBPT) under different soil water contents to provide a basis for the efficient utilization of nitrogen fertilizer in agricultural production in karst areas. Four nitrogen fertilizers (e.g., ammonium bicarbonate, ammonium sulfate, ammonium chloride, and urea) were applied separately and combined with oxalic acid, DMPP, and NBPT. The ammonium and nitrate nitrogen contents in the different soil layers were measured. The soil columns were cultured through an indoor soil column simulation at water content levels of 30%, 40%, and flooded (50%) for 30 days. Ammonium bicarbonate with inhibitors increased soil NH4 +-N content by 15.42-21.12%. Ammonium sulfate with oxalic acid or NBPT increased soil NH4 +-N content by 27.56-52.25% at 30% and 40% moisture content treatments, compared to ammonium sulfate alone. Urea with DMPP application significantly increased soil NH4 +-N content by 11.93-14.87% at 40% water content and flooded conditions. In all treatments, the NH4 +-N content in the soil treated with 30% water content of ammonium chloride with oxalic acid was the highest. The NH4 +-N content showed a decreasing trend with an increase in the water content. The NO3 --N content in soil treated with ammonium bicarbonate and DMPP was higher than that treated with other nitrogen fertilizers at 30% moisture. The NO3 --N content decreased with increased water content. Under all treatments, ammonium chloride with oxalic acid had the highest percentage of soil NH4 +-N and soil soluble inorganic nitrogen at 30% water content, with 55.29% and 55.97%, respectively. Among the nitrogen fertilizer treatments, the soil NH4 +-N content increased in ammonium bicarbonate with DMPP or NBPT, ammonium sulfate with oxalic acid or NBPT, and urea with DMPP. The four nitrogen fertilizers with DMPP increased the soil NO3 --N content. Nitrogen fertilizer combined with oxalic acid and inhibitors could effectively improve the effective use of nitrogen fertilizer.

Effect of carboxylic acids on the properties of zerovalent iron toward adsorption and degradation of trichloroethylene

Enhanced remediation of Cr(VI)-contaminated soil by modified zero-valent iron with oxalic acid on biochar

Large amounts of chemical fertilizers are still currently used to compensate the soil nutrients scarcity in order to increase and sustain crop yield with consequent rising of environmental pollution and health problems. To mitigate these environmental risks, fertilizers with slow-release behaviours have been developed. The aim of this study was to assess the agronomic potential of two different glass-based materials (by-products from the ceramic sector) as inorganic slow-release iron (Fe) fertilizers. The X-ray powder diffraction confirmed the presence of amorphous structure and the richness in Fe of the investigated materials. The solubility analysis highlighted the slow Fe release from the glassy network and that the maximum of the Fe release was at alkaline pH suggesting their potential use as slow-release Fe fertilizers, especially in calcareous soils. The pot and leaching experiments demonstrated that although the glass-based materials increased the amount of soil available Fe, we did not observe Fe leaching and plant toxicity. This fact would suggest their reliability to increase soil fertility without negative effects on the environment. The use of glass-based materials, specifically by-products from the ceramic sectors, as inorganic slow-release Fe fertilizers can be sustained. The tests performed at three different pH conditions testified the slow-release behaviour of the tested materials and underlined that the Fe release increases at alkaline environment. Therefore, the present study pointed out the glass-based materials by products from the ceramic sector as novel slow-release and environmental-friendly fertilizers in agriculture. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

By analyzing the kinetics of heterogeneous (electrode) and homogeneous reduction for benzyl phenyl ether it was found that toluene and phenol are formed via the transfer of two electrons and the breaking of the PhO-Bz bond. It was shown that electron transfer constitutes the slow stage in heterogeneous and homogeneous reduction. The homogeneous transfer coefficient was approximately 0.5, which represents a significant difference from the heterogeneous value.

Immobilization of arsenic in soils by stabilized nanoscale zero-valent iron, iron sulfide (FeS), and magnetite (Fe3O4) particles

Soil contamination of ammunition residues at shooting ranges for small arms may be followed by leaching of lead (Pb), copper (Cu), zinc (Zn), and antimony (Sb). Mixing stabilizing agents into the soil may reduce the mobility of the contaminants. To avoid risk of unexpected effects of a stabilizing agent in large-scale measures, the effect of an amendment should be tested on a small scale in advance. Two different amendments, ferric oxyhydroxide powder (CFH-12 from a commercial provider) and zerovalent iron (powder or grit), were mixed into different soil types in order to test their generic effects as stabilizing agents in contaminated soil from shooting ranges. Factors that were considered for their effects were soil water pH, limestone addition, soil chemical composition, and content of organic matter. The stabilizing agents (2–4% weight basis) were mixed into four different soil types contaminated with ammunition residues. The effects of the amendments were elucidated in two column experiments, one small-scale and one larger-scale experiment. Leaching of Pb, Cu, Zn, and Sb from the soil mixed with stabilizing agents was compared with reference soil with no amendments added. Best performance was achieved on leaching of Sb irrespective of the type of iron amendment and soil type. The Sb concentrations in the soil leachates were 55–94% less than in the leachates from the reference soils. Both amendments mixed into an acidic soil reduced the Pb, Cu, and Zn concentrations in the soil leachates in the range of 79–99%. The ability of the amendment to reduce leaching of Pb, Cu, and Zn from the other soil types was highly dependent on soil pH. CFH-12 was acidic and pH had to be balanced with limestone. The general trend was that the iron amendments reduced leaching of the elements in the order Sb>>Cu > Pb ≥ Zn. Iron amendment may be suitable as stabilizing agents for Pb, Cu, Zn, and Sb in soil. The soil pH appeared to be the most important factor governing the mobility of the ammunition residues in the soils. Overall, best effect was achieved with zerovalent iron, which can be purchased at low cost and appeared to have minor influence on the properties of the soils.

While biologically mediated reductive dechlorination continues to be a significant focus of chlorinated solvent remediation, there has been an increased interest in abiotic reductive processes for the remediation of chlorinated solvents. In situ chemical reduction (ISCR) uses zero‐valent iron (ZVI)–based technologies, such as nanoscale iron and bimetallic ZVI, as well as naturally occurring reduced minerals incorporating dual‐valent iron (DVI), such as magnetite, green rust, and iron sulfides that are capable of dechlorinating solvents. A more recent area of development in ISCR has been in combining biological and abiotic processes.There are several ways in which biological and abiotic processes can be combined. First, the interaction between the two may be “causative.” For example, the Air Force Center for Engineering and the Environment's biogeochemical reductive dechlorination (BiRD) technology combines a mulch barrier with hematite and gypsum to create an iron‐sulfide‐based reducing zone. Biodegradation under sulfate‐reducing conditions produces sulfide that combines with the hematite to form iron sulfides. As such, the BiRD technology is “causative”; the biological processes create reducing minerals. The biological generation of other reducing minerals such as magnetite, siderite, and green rust is feasible and is, with magnetite, observed in nature at some petroleum sites. A second type of interaction between abiotic and biotic processes is “synergistic.” For example, biological processes can enhance the activity of reduced metals/minerals. This is the basis of the EHC® ISCR technologies, which combine ZVI with a (slowly) degradable carbon substrate. This combination rapidly creates buffered, strongly reducing conditions, which result in more complete solvent degradation (i.e., direct mineralization). The extent and level of reducing activity commonly observed are much greater when both the carbon substrate and the ZVI are present. When the carbon substrate is expended, the reducing activity due to ZVI alone is much less. The understanding of biogeochemical processes and their impact on abiotic processes is still developing. As that understanding develops, new and improved methods will be created to enhance volatile organic compound destruction. © 2009 Wiley Periodicals, Inc.