Investigation of copper sorption by sugar beet processing lime waste

In the western US, sugar beet processing for sugar recovery generates a lime-based waste product (~250,000 megagrams/yr) that has little liming value in the region’s calcareous soils. This area has recently experienced an increase in dairy production, with dairies utilizing copper-based hoof baths to prevent hoof diseases. A concern exists regarding soil copper accumulation as spent hoof baths may be disposed of in waste ponds with pond waters utilized for irrigation. The objective of this preliminary study was to evaluate the ability of lime waste to sorb copper. Lime waste was mixed with increasing copper-containing solutions (up to 100,000 mg/kg), at various buffered pH values (6, 7, 8, 9), and shaken over various time periods (up to 30 days). Copper sorption phenomenon was quantified using sorption maximum fitting and sorption mechanism was investigated using X-ray absorption spectroscopy. Results showed that sorption onto lime waste increased with decreasing pH, and the maximum copper sorption of ~40,000 mg/kg occurred at pH 6. X-ray absorption spectroscopy indicated that copper hydroxide was the probable species present, although the precipitate existed as small multinuclear precipitates on the surface of the lime waste. Such structures may be precursors for larger surface precipitates that develop over longer incubation times. Findings suggest that sugar beet processing lime waste can viably sorb Cu from liquid waste streams, and thus it may have the ability to remove Cu from spent hoof baths

Selenium adsorption to aluminum-based water treatment residuals

Aluminum-based water treatment residuals (WTR) can adsorb water- and soil-borne P, As(V), As(III), and perchlorate, and may be able to adsorb excess environmental selenium. WTR, clay minerals, and amorphous aluminum hydroxide were shaken for 24 h in selenate or selenite solutions at pH values of 5–9, and then analyzed for selenium content. Selenate and selenite adsorption edges were unaffected across the pH range studied. Selenate adsorbed on to WTR, reference mineral phases, and amorphous aluminum hydroxide occurred as outer sphere complexes (relatively loosely bound), while selenite adsorption was identified as inner-sphere complexation (relatively tightly bound). Selenite sorption to WTR in an anoxic environment reduced Se(IV) to Se(0), and oxidation of Se(0) or Se(IV) appeared irreversible once sorbed to WTR. Al-based WTR could play a favorable role in sequestering excess Se in affected water sources

Biochars impact on soil moisture storage in an Ultisol and two Aridisols

Excessive copper concentrations in water systems can negatively impact biological systems. Because copper can form strong associations with organic functional groups, we examined the ability of biochar (a carbon-enriched organic bioenergy by-product) to sorb copper from solution. In a batch experiment, potassium hydroxide-steam activated pecan shell biochar was shaken for 24 hours in pH 6, 7, 8, or 9 buffered solutions containing various copper concentrations to identify effect of pH on biochar copper sorption. Afterwards, all biochar solids from the 24 hours shaking period were air-dried and then analyzed using X-ray absorption fine structure spectroscopy to determine solid-phase copper speciation. In a separate batch experiment, biochar was shaken for 30 days in pH 6 buffered solution containing increasing copper concentrations; the copper sorption maximum was calculated based on the exponential rise to a maximum equation. Biochar sorbed increasing amounts of copper as the solution pH decreased from 9 to 6. The X-ray absorption fine structure results revealed that copper was predominantly sorbed onto a biochar organic phase at pH 6 in a molecular structure similar to copper adsorbed on humic acid. The X-ray absorption fine structure spectra at pH 7, 8, and 9 suggested that copper was associated with the biochar as three phases: 1) a complex adsorbed on organic ligands similar to copper on humic acid; 2) carbonate phases similar to azurite; and 3) a copper oxide phase like tenorite. The exponential rise equation fit to the incubated samples predicted a copper sorption maximum of 42,300 mg/kg copper. The results showed that potassium hydroxide-steam activated pecan shell biochar could be utilized as a material for sorbing excess copper from water systems, potentially reducing the negative effects of copper in the environment

Biochars impact on soil moisture storage in an Ultisol and two Aridisols

Excessive copper concentrations in water systems can negatively impact biological systems. Because copper can form strong associations with organic functional groups, we examined the ability of biochar (a carbon-enriched organic bioenergy by-product) to sorb copper from solution. In a batch experiment, potassium hydroxide-steam activated pecan shell biochar was shaken for 24 hours in pH 6, 7, 8, or 9 buffered solutions containing various copper concentrations to identify effect of pH on biochar copper sorption. Afterwards, all biochar solids from the 24 hours shaking period were air-dried and then analyzed using X-ray absorption fine structure spectroscopy to determine solid-phase copper speciation. In a separate batch experiment, biochar was shaken for 30 days in pH 6 buffered solution containing increasing copper concentrations; the copper sorption maximum was calculated based on the exponential rise to a maximum equation. Biochar sorbed increasing amounts of copper as the solution pH decreased from 9 to 6. The X-ray absorption fine structure results revealed that copper was predominantly sorbed onto a biochar organic phase at pH 6 in a molecular structure similar to copper adsorbed on humic acid. The X-ray absorption fine structure spectra at pH 7, 8, and 9 suggested that copper was associated with the biochar as three phases: 1) a complex adsorbed on organic ligands similar to copper on humic acid; 2) carbonate phases similar to azurite; and 3) a copper oxide phase like tenorite. The exponential rise equation fit to the incubated samples predicted a copper sorption maximum of 42,300 mg/kg copper. The results showed that potassium hydroxide-steam activated pecan shell biochar could be utilized as a material for sorbing excess copper from water systems, potentially reducing the negative effects of copper in the environment

Chemical characterisation, antibacterial activity, and (nano)silver transformation of commercial personal care products exposed to household greywater

The objective of this study was to test the original speciation of silver (Ag) in eight different commercially available personal care products and investigate the chemical transformation of Ag during exposure to two types of synthetic greywater. The antimicrobial activity of the products was examined to determine the relationship between Ag content and speciation with the antibacterial functionality of the products. The Ag content of each product was quantified and X-ray absorption near-edge structure (XANES) analysis was used to investigate the initial speciation in the products and the changes occurring upon mixture with greywater. The results showed that the total Ag concentration in the products ranged from 17 to 30 mg kg-1, and was usually below the value reported on the label. Analyses revealed the complexity of Ag speciation in these products and highlighted the importance of characterisation studies to help elucidate the potential risks of nano-Ag in the environment. The antibacterial results confirmed that the antibacterial efficacy of the products depends on the concentration, form and speciation of Ag in the products, but is also significantly affected by product formulation. For instance, many of the products contained additional bactericidal ingredients, making it difficult to determine how much of the bactericidal effect was due directly to the Ag content/species. This paper offers some suggestions for standard methodologies to facilitate cross-comparison of potential risks across different studies and nano-enabled products. This journal is © The Royal Society of Chemistry

Labile lead in polluted soils measured by stable isotope dilution

It is well known that lead (Pb) is strongly immobilized in soil by adsorption or precipitation. However, the reversibility of these reactions is poorly documented. In this study, the isotopically exchangeable Pb concentration in soils (E-value) was measured using a stable isotope (²⁰⁸Pb). Soils were collected at three industrialized sites where historical Pb emissions have resulted in elevated Pb concentrations in the surrounding soil. Lead concentrations ranged from background values, in the control soils collected far from the emission source, to highly elevated concentrations (5460–14440 mg Pb kg⁻¹). The control soil of each site was amended in the laboratory with Pb(NO₃)₂ to the same total Pb concentrations as the field-contaminated soils. The %E values (E-value relative to total Pb content) were greater than 84% in the laboratory-amended soils, and ranged from 45% to 78% (mean 58%) in the field-contaminated soils. The relatively large labile fractions of Pb in the field-contaminated soils show that the majority of Pb is reversibly bound despite the fact that the binding strength is large. The Pb concentrations in soil solution were up to 3500-fold larger for the laboratory-amended soils than for field-contaminated soils at corresponding total Pb concentrations. These differences cannot be explained by differences in labile fractions of Pb but are attributed to the decrease in soil solution pH upon addition of Pb²⁺-salt.F. Degryse, N. Waegeneers & E. Smolder

Dynamics of lead bioavailability and speciation in indoor dust and x-ray spectroscopic investigation of the link between ingestion and inhalation pathways

Lead (Pb) exposure from household dust is a major childhood health concern because of its adverse impact on cognitive development. This study investigated the absorption kinetics of Pb from indoor dust following a single dose instillation into C57BL/6 mice. Blood Pb concentration (PbB) was assessed over 24 h, and the dynamics of particles in the lung and gastro-intestinal (GI) tract were visualized using X-ray fluorescence (XRF) microscopy. The influence of mineralogy on Pb absorption and particle retention was investigated using X-ray absorption near-edge structure spectroscopy. A rapid rise in PbB was observed between 0.25 and 4 h after instillation, peaking at 8 h and slowly declining during a period of 24 h. Following clearance from the lungs, Pb particles were detected in the stomach and small intestine at 4 and 8 h, respectively. Analysis of Pb mineralogy in the residual particles in tissues at 8 h showed that mineral-sorbed Pb and Pb-phosphates dominated the lung, while organic-bound Pb and galena were the main phases in the small intestines. This is the first study to visualize Pb dynamics in the lung and GI tract using XRF microscopy and link the inhalation and ingestion pathways for metal exposure assessment from dust.Farzana Kastury, Euan Smith, Enzo Lombi, Martin W. Donnelley, Patricia L. Cmielewski, David W. Parsons, Matt Noerpel, Kirk G. Scheckel, Andrew M. Kingston, Glenn R. Myers, David Paterson, Martin D. de Jonge, and Albert L. Juhas