Phosphorus recovery and recycling from model animal wastewaters using materials prepared from rice straw and corn cobs.

Anthropogenic loss of phosphorus to surface waters not only causes environmental problems but depletes valuable phosphorus reserves. In this study, magnesium amended biochars and magnesium silicate, synthesized from corn cobs and rice straw, respectively, were evaluated for phosphorus uptake including the effects of pH and alkalinity. The overall goal was to close the phosphorus loop by recovering phosphorus from animal waste and reusing it as fertilizer.

Transformation of mackinawite to greigite by trichloroethylene and tetrachloroethylene.

Trichloroethylene (TCE) and tetrachloroethylene (PCE) are common ground water contaminants susceptible to reductive dechlorination by FeS (mackinawite) in anaerobic environments. The objective of this study was to characterize the mineral-associated products that form when mackinawite reacts with TCE and PCE. The dissolved products of the reaction included Cl and Fe, and trace amounts of cis 1,2-dichloroethylene (for TCE) and TCE (for PCE).

Iron-Sulfide-Associated Products Formed during Reductive Dechlorination of Carbon Tetrachloride.

This paper investigated the mackinawite (FeS)-associated products formed during reaction between FeS and carbon tetrachloride (CT) at pH 7 and 8. At pH 8, reaction of FeS with CT led to formation of abundant spherical particles with diameters between 50 and 400 nm on the FeS surface and in solution; far fewer such particles were observed at pH 7. Analysis of the FeS surface by energy dispersive X-ray spectroscopy after reaction with CT at pH 8 showed decreased sulfur and elevated oxygen compared to unreacted FeS.

Biological versus mineralogical chromium reduction: potential for reoxidation by manganese oxide.

Hexavalent chromium (Cr(vi), present predominantly as CrO4(2-) in water at neutral pH) is a common ground water pollutant, and reductive immobilization is a frequent remediation alternative. The Cr(iii) that forms upon microbial or abiotic reduction often co-precipitates with naturally present or added iron (Fe), and the stability of the resulting Fe-Cr precipitate is a function of its mineral properties. In this study, Fe-Cr solids were formed by microbial Cr(vi) reduction using Desulfovibrio vulgaris strain RCH1 in the presence of the Fe-bearing minerals hematite, aluminum substituted goethite (Al-goethite), and nontronite (NAu-2, Clay Minerals Society), or by abiotic Cr(vi) reduction by dithionite reduced NAu-2 or iron sulfide (FeS).

Synthesis, characterization, and evaluation of simple aluminum-based adsorbents for fluoride removal from drinking water.

Simple aluminum (hydr)oxides and layered double hydroxides were synthesized using common chemicals and equipment by varying synthesis temperature, concentrations of extra sulfate and citrate, and metal oxide amendments. Aluminum (hydr)oxide samples were aged at either 25 or 200°C during synthesis and, in some cases, calcined at 600 °C. Despite yielding increased crystallinity and mineral phase changes, higher temperatures had a generally negative effect on fluoride adsorption.

Comparison of four advanced oxidation processes for the removal of naphthenic acids from model oil sands process water.

Four advanced oxidation processes (UV/TiO(2), UV/IO(4)(-), UV/S(2)O(8)(2-), and UV/H(2)O(2)) were tested for their ability to mineralize naphthenic acids to inorganic carbon in a model oil sands process water containing high dissolved and suspended solids at pH values ranging from 8 to 12. A medium pressure mercury (Hg) lamp was used, and a Quartz immersion well surrounded the lamp. The treatment goal of 5mg/L naphthenic acids (3.

Impacts of microbial community composition on isotope fractionation during reductive dechlorination of tetrachloroethylene.

Isotope fractionation has been used with increasing frequency as a tool to quantify degradation of chlorinated aliphatic pollutants in the environment. The objective of this research was to determine if the electron donor present in enrichment cultures prepared from uncontaminated sediments influenced the extent of isotope fractionation of tetrachloroethylene (PCE), either directly, or through its influence on microbial community composition. Two PCE-degrading enrichment cultures were prepared from Duck Pond (DP) sediment and were incubated with formate (DPF) or H(2) (DPH) as electron donor.

Effects of natural organic matter model compounds on the transformation of carbon tetrachloride by chloride green rust.

Interest has grown in the use of reactive minerals for natural and engineered transformation of ground water contaminants. This study investigated how the structural properties of 10 model compounds representing natural organic matter (NOM) influenced their adsorption to chloride green rust (GR-Cl), and how this adsorption affected rate constants for transformation of carbon tetrachloride (CT) by GR-Cl. The affinity of benzoic acid, phthalic acid, trimesic acid, pyromellitic acid, and mellitic acid for the GR-Cl surface generally increased in the order of increasing number of carboxylic acid functional groups, increasing acidity of these functional groups, and increasing charge density.

Influence of soil minerals on the rates and products of abiotic transformation of carbon tetrachloride in anaerobic soils and sediments.

Rates and products of abiotic mineral-mediated carbon tetrachloride (CT) transformation were measured in microcosms prepared from natural soils and sediments that were incubated under iron-reducing and sulfate-reducing conditions, then sterilized to inhibit microbial activity. For one set of microcosms, the rate of CT disappearance was correlated with the concentration of weakly bound (MgCl2 extractable) Fe(II) in an experiment in which CT was repeatedly spiked into the microcosms. When pooling the results from all microcosms, however, there was no statistically significant positive correlation between CT transformation rate and the concentration of weakly bound Fe(II) or any other mineral species.

The relative contributions of abiotic and microbial processes to the transformation of tetrachloroethylene and trichloroethylene in anaerobic microcosms.

Reductive dechlorination of tetrachloroethylene (PCE) and trichloroethylene (TCE) was studied in well-defined microcosms prepared with aquifer materials from three locations. Electron donors and terminal electron acceptors were added to both stimulate microbial activity and generate reactive minerals via microbial iron and sulfate reduction. The relative importance of abiotic and microbial PCE and TCE reductive dechlorination was then assessed by analysis of reaction products and kinetics and, in some cases, by stable carbon isotope fractionation.

Kinetic and isotope analyses of tetrachloroethylene and trichloroethylene degradation by model Fe(II)-bearing minerals.

The kinetics and in some cases stable carbon isotope fractionation associated with abiotic reductive dechlorination of tetrachloroethylene (PCE) and trichloroethylene (TCE) by model Fe(II)-bearing minerals present in anaerobic soils were measured. The minerals studied were chloride green rust (GR-Cl), sulfate green rust (GR-SO(4)), pyrite, magnetite, and adsorbed Fe(II) or FeS formed at the surface of goethite by treatment with dissolved Fe(II) or S(-II). We observed some abiotic transformation of PCE and TCE in every system studied, as evidenced by the presence of abiotic reaction products.

Photocatalytic oxidation of aqueous ammonia in model gray waters.

This study investigated the TiO2 photocatalytic degradation of aqueous ammonia (NH4+/NH3) in the presence of surfactants and monosaccharides at pH approximately 10.1. Initial rates of NH4+/NH3 photocatalytic degradation decreased by approximately 50-90% in the presence of anionic, cationic, and nonionic surfactants and monosaccharides.

Distinguishing abiotic and biotic transformation of tetrachloroethylene and trichloroethylene by stable carbon isotope fractionation.

Significant carbon isotope fractionation was observed during FeS-mediated reductive dechlorination of tetrachloroethylene (PCE) and trichloroethylene (TCE). Bulk enrichment factors (E(bulk)) for PCE were -30.2 +/- 4.

The influence of iron and sulfur mineral fractions on carbon tetrachloride transformation in model anaerobic soils and sediments.

The objective of this research was to identify the dissolved species or solid phase mineral fraction(s) best correlated with rates of carbon tetrachloride (CT) reductive transformation in systems modeling sulfate-reducing and iron oxide-rich soils and sediments. We used sulfide (S(-II))-treated goethite as our model system, but also studied Fe(II) and S(-II)-treated goethite, Fe(II)-treated goethite, pure FeS, and Fe(II)-treated FeS in order to isolate and evaluate the influence of different mineral fractions on reaction rates. Initial rates of CT transformation were measured for different pH values and concentrations of added Fe(II), as well as different aging times and conditions.

Effects of pH and catalyst concentration on photocatalytic oxidation of aqueous ammonia and nitrite in titanium dioxide suspensions.

Batch experiments were conducted to study the effects of titanium dioxide (TiO2) concentration and pH on the initial rates of photocatalytic oxidation of aqueous ammonium/ ammonia (NH4+/NH3) and nitrite (NO2-) in UV-illuminated TiO2 suspensions. While no simple kinetic model could fit the data at lower TiO2 concentrations, at TiO2 concentrations > or = 1 g/L, the experimental data were consistent with a model assuming consecutive first-order transformation of NH4+/NH3 to NO2- and NO2- to nitrate (NO3-). For TiO2 concentrations > or = 1 g/L, the rate constants for NO2 photocatalytic oxidation to NO3 were far more dependent on TiO2 concentration than were those for NH4+/NH3 oxidation to NO2-, suggesting that, without sufficient TiO2, complete oxidation of NH4+/NH3 to NO3- will not occur.

Effects of iron purity and groundwater characteristics on rates and products in the degradation of carbon tetrachloride by iron metal.

Carbon tetrachloride (CT) batch degradation experiments by four commercial irons at neutral pH indicated that iron metal (Fe0) purity affected both rates and products of CT transformation in anaerobic systems. Surface-area-normalized rate constants and elemental composition analysis of the untreated metals indicate that the highest-purity, least-oxidized Fe0 was the most reactive on a surface-area-normalized basis in transforming CT. There was also a trend of increasing yield of the hydrogenolysis product chloroform (CF) with increasing Fe0 purity.