Arsenic removal from water/wastewater using adsorbents—A critical review

The increasing worldwide contamination of freshwater systems with thousands of industrial and natural chemical compounds is one of the key environmental problems facing humanity. Although most of these compounds are present at low concentrations, many of them raise considerable toxicological concerns, particularly when present as components of complex mixtures. Here we review three scientific challenges in addressing water-quality problems caused by such micropollutants. First, tools to assess the impact of these pollutants on aquatic life and human health must be further developed and refined. Second, cost-effective and appropriate remediation and water-treatment technologies must be explored and implemented. Third, usage and disposal strategies, coupled with the search for environmentally more benign products and processes, should aim to minimize introduction of critical pollutants into the aquatic environment.

https://science.sciencemag.org/content/sci/313/5790/1072.full.pdf

The Challenge of Micropollutants in Aquatic Systems

The finding that total viral abundance is higher than total prokaryotic abundance and that a significant fraction of the prokaryotic community is infected with phages in aquatic systems has stimulated research on the ecology of prokaryotic viruses and their role in ecosystems. This review treats the ecology of prokaryotic viruses ('phages') in marine, freshwater and soil systems from a 'virus point of view'. The abundance of viruses varies strongly in different environments and is related to bacterial abundance or activity suggesting that the majority of the viruses found in the environment are typically phages. Data on phage diversity are sparse but indicate that phages are extremely diverse in natural systems. Lytic phages are predators of prokaryotes, whereas lysogenic and chronic infections represent a parasitic interaction. Some forms of lysogeny might be described best as mutualism. The little existing ecological data on phage populations indicate a large variety of environmental niches and survival strategies. The host cell is the main resource for phages and the resource quality, i.e., the metabolic state of the host cell, is a critical factor in all steps of the phage life cycle. Virus-induced mortality of prokaryotes varies strongly on a temporal and spatial scale and shows that phages can be important predators of bacterioplankton. This mortality and the release of cell lysis products into the environment can strongly influence microbial food web processes and biogeochemical cycles. Phages can also affect host diversity, e.g., by 'killing the winner' and keeping in check competitively dominant species or populations. Moreover, they mediate gene transfer between prokaryotes, but this remains largely unknown in the environment. Genomics or proteomics are providing us now with powerful tools in phage ecology, but final testing will have to be performed in the environment.

Ecology of prokaryotic viruses

Chromium occurrence in the environment and methods of its speciation.

Plastic litter is widely acknowledged as a global environmental threat, and poor management and disposal lead to increasing levels in the environment. Of recent concern is the degradation of plastics from macro- to micro- and even to nanosized particles smaller than 100 nm in size. At the nanoscale, plastics are difficult to detect and can be transported in air, soil, and water compartments. While the impact of plastic debris on marine and fresh waters and organisms has been studied, the loads, transformations, transport, and fate of plastics in terrestrial and subsurface environments are largely overlooked. In this Critical Review, we first present estimated loads of plastics in different environmental compartments. We also provide a critical review of the current knowledge vis-a-vis nanoplastic (NP) and microplastic (MP) aggregation, deposition, and contaminant cotransport in the environment. Important factors that affect aggregation and deposition in natural subsurface environments are identified and c...

/pdf/microplastics-and-nanoplastics-in-aquatic-environments-151u4ngf12.pdf

Microplastics and Nanoplastics in Aquatic Environments: Aggregation, Deposition, and Enhanced Contaminant Transport

https://stormwater.ucf.edu/fileRepository/docs/chemicaltreatment/documents/Blowes%20et%20al.,%202000.pdf

Treatment of inorganic contaminants using permeable reactive barriers

Batch tests were performed to evaluate the effects of inorganic anion competition on the kinetics of arsenate (As(V)) and arsenite (As(III)) removal by zerovalent iron (Peerless Fe0) in aqueous solution. The oxyanions underwent either sorption-dominated reactions (phosphate, silicate, carbonate, borate, and sulfate) or reduction-dominated reactions (chromate, molybdate, and nitrate) with Peerless Fe0 in the presence of As(V) or As(III), relative to chloride. Pseudo-first-order rate equations were found to describe satisfactorily both As(V) and As(III) removal kinetics in the presence of each competing anion. Of the oxyanions tested for Peerless Fe0 in the pH range from 7 to 9, phosphate caused the greatest decrease in As removal rate (7.0 × 10-3 to 18.5 × 10-3 h-1) relative to chloride (34.9 × 10-3 to 36.2 × 10-3 h-1). Silicate, chromate, and molybdate also caused strong inhibition of As removal, followed by carbonate and nitrate, whereas borate and sulfate only caused slight inhibition to As(III) removal...

/pdf/arsenate-and-arsenite-removal-by-zerovalent-iron-effects-of-uomd84mdfq.pdf

Arsenate and Arsenite Removal by Zerovalent Iron: Effects of Phosphate, Silicate, Carbonate, Borate, Sulfate, Chromate, Molybdate, and Nitrate, Relative to Chloride

Batch tests were performed utilizing four zerovalent iron (Fe0) filings (Fisher, Peerless, Master Builders, and Aldrich) to remove As(V) and As(III) from water. One gram of metal was reacted headspace-free at 23 °C for up to 5 days in the dark with 41.5 mL of 2 mg L-1 As(V), or As(III) or As(V) + As(III) (1:1) in 0.01 M NaCl. Arsenic removal on a mass basis followed the order:  Fisher > Peerless ≈ Master Builders > Aldrich; whereas, on a surface area basis the order became:  Fisher > Aldrich > Peerless ≈ Master Builders. Arsenic concentration decreased exponentially with time, and was below 0.01 mg L-1 in 4 days with the exception of Aldrich Fe0. More As(III) was sorbed than As(V) by Peerless Fe0 in the initial As concentration range between 2 and 100 mg L-1. No As(III) was detected by X-ray photoelectron spectroscopy (XPS) on Peerless Fe0 at 5 days when As(V) was the initial arsenic species in the solution. As(III) was detected by XPS at 30 and 60 days present on Peerless Fe0, when As(V) was the initial ...

Arsenate and arsenite removal by zerovalent iron: kinetics, redox transformation, and implications for in situ groundwater remediation.

The reduction of chromium from the Cr(VI) to the Cr(III) state by the presence of elemental, or zero-oxidation-state, iron metal was studied to evaluate the feasibility of such a process for subsurface chromate remediation. Reactions were studied in systems of natural aquifer materials with varying geochemistry. Different forms of iron metal had significantly different abilities to reduce chromate, ranging from extremely rapid to essentially no effect. Impure, partially oxidized iron was most effective, with iron quantity being the most important rate factor, followed by aquifer material type and solid :solution ratio. Evidence for chromium-iron hydroxide solid solution (Cr x, Fe 1-x )(OH) 3 (ss) formation was obtained by electron probe microanalysis. A cyclic, multiple reaction electrochemical corrosion mechanism, enhanced by the development of an electrical double-layer analogue, is proposed to explain the differing iron reactivities and aquifer material effects.

Coupled Iron Corrosion and Chromate Reduction: Mechanisms for Subsurface Remediation

http://www.okepscor.org/sites/default/files/u6/1-s2.0-S0883292799000104-main.pdf

The application of in situ permeable reactive (zero-valent iron) barrier technology for the remediation of chromate-contaminated groundwater: a field test

Robert W. Puls

Papers

Treatment of inorganic contaminants using permeable reactive barriers

Arsenate and Arsenite Removal by Zerovalent Iron: Effects of Phosphate, Silicate, Carbonate, Borate, Sulfate, Chromate, Molybdate, and Nitrate, Relative to Chloride

Arsenate and arsenite removal by zerovalent iron: kinetics, redox transformation, and implications for in situ groundwater remediation.

Coupled Iron Corrosion and Chromate Reduction: Mechanisms for Subsurface Remediation

The application of in situ permeable reactive (zero-valent iron) barrier technology for the remediation of chromate-contaminated groundwater: a field test