Iron supported on bioinspired green silica for water remediation.

Iron has been used previously in water decontamination, either unsupported or supported on clays, polymers, carbons or ceramics such as silica. However, the reported synthesis procedures are tedious, lengthy (involving various steps), and either utilise or produce toxic chemicals. Herein, the use of a simple, rapid, bio-inspired green synthesis method is reported to prepare, for the first time, a family of iron supported on green nanosilica materials (Fe@GN) to create new technological solutions for water remediation. In particular, Fe@GN were employed for the removal of arsenate ions as a model for potentially toxic elements in aqueous solution. Several characterization techniques were used to study the physical, structural and chemical properties of the new Fe@GN. When evaluated as an adsorption platform for the removal of arsenate ions, Fe@GN exhibited high adsorption capacity (69 mg of As per g of Fe@GN) with superior kinetics (reaching ∼35 mg As per g sorbent per hr) - threefold higher than the highest removal rates reported to date. Moreover, a method was developed to regenerate the Fe@GN allowing for a full recovery and reuse of the adsorbent in subsequent extractions; strongly highlighting the potential technological benefits of these new green materials.

Field application of a rapid spectrophotometric method for determination of persulfate in soil.

Remediation of hydrocarbon contaminated soils can be performed both in situ and ex situ using chemical oxidants such as sodium persulfate. Standard methods for quantifying persulfate require either centrifugation or prolonged settling times. An optimized soil extraction procedure was developed for persulfate involving simple water extraction using a modified disposable syringe. This allows considerable saving of time and removes the need for centrifugation. The extraction time was reduced to only 5 min compared to 15 min for the standard approach. A comparison of the two approaches demonstrated that each provides comparable results. Comparisons were made using high (93 g kg(-1) soil) and low (9.3 g kg(-1) soil) additions of sodium persulfate to a petroleum hydrocarbon-contaminated soil, as well as sand spiked with diesel. Recoveries of 95±1% and 96±10% were observed with the higher application rate in the contaminated soil and spiked sand, respectively. Corresponding recoveries of 86±5% and 117±19% were measured for the lower application rate. Results were obtained in only 25 min and the method is well suited to batch analyses. In addition, it is suitable for application in a small field laboratory or even a mobile, vehicle-based system, as it requires minimal equipment and reagents.

Biochar diminishes nitrous oxide and nitrate leaching from diverse nutrient sources.

Manure generated by intensive livestock operations poses potential ecological risk in the form of water pollution and greenhouse gas emission. To assess the impact of biochar on coarse-textured soils under contrasting nutrient management regimes, a 55-d incubation was conducted using unplanted soil columns amended with manure, slurry, or fertilizer (plus unamended control), each with or without biochar applied at 2% soil mass (dry weight basis). Under repeated leaching, the cumulative NO emission from the columns was significantly affected by the presence of biochar ( < 0.0001), although these data were not normally distributed. Results indicated that the biochar-amended soils emitted significantly less NO than their unamended counterparts, with the exception of manure-amended soils. The presence of biochar increased the pH of column leachate by 0.08 to 1.70 and significantly decreased the cumulative amount of mineral N leached from the soil. The presence of biochar significantly increased the amount of PO-P in soil leachate, but there was no significant difference between the means for any of the amendments used on their own relative to their biochar-amended counterparts. The data demonstrate that biochar could potentially aid in the mitigation of NO emissions from certain soils and in N loss in leachate from soil amended with slurry, manure, or fertilizer used in livestock systems.

Preconcentration and selective extraction of chromium species in water samples using amino modified mesoporous silica.

Speciation and separation of chromium (VI) and chromium (III) from aqueous solutions were investigated using amino-propyl functionalised mesoporous silica (AP-MCM-41) as an adsorbent. The as-synthesised adsorbent was produced following a simple synthesis method at room temperature prior to template removal using microwave digestion. The maximum adsorption capacity at 111.1 mg/g was calculated according to the Langmuir isotherm model, suggesting a 1:1 monolayer adsorption mechanism. Moreover, AP is a simple chelate, yet it can extract Cr (VI) exclusively from solutions containing other mixed metal ions simply by tuning the solution pH. Recovery of Cr (VI) from loaded sorbents is equally easy to perform with 100% extraction efficiencies allowing reuse of the sorbent and recovery of Cr (VI) from aqueous solutions containing a complex mixture of ions. The material would find use in environmental remediation applications, as a selective adsorbent of Cr (VI) or even as a solid-phase extraction stationary phase to remove and pre-concentrate Cr (VI) from aqueous solutions; this study demonstrates enrichment factors of 100 although higher levels are also possible.