The present invention relates to a method of removing chromate ions from an ion-exchange effluent, the method comprising: (i) providing an ion-exchange effluent comprising chromate ions obtained from the regeneration of an ion-exchange material, (ii) admixing the ion-exchange effluent with a source of alkali metal dithionite to form a first precipitate, and (iii) removing the first precipitate

Compositions containing a porous organic polymer and a heavy metal chelating moiety are provided for binding heavy metals, for example in remediation and purification. The compositions can be stable and recyclable. The compositions can contain heavy metal chelating moieties such as a thiol, a sulfide, an amine, a pyridine, or a combination thereof. The compositions can bind heavy metals such as lead, cadmium, and mercury. The compositions can have a large surface area greater than about 20 m.sup.2/g. The compositions can be used for remediation and purification to remove heavy metals from a solution. The compositions can have a maximum metal uptake capacity of more than 500 mg g.sup.−1 and/or a metal distribution coefficient of at least 1×10.sup.7 mL g.sup.−1 at 1 atm and 296 K. Methods of making the compositions are provided. Methods of binding heavy metals in remediation and purification are also provided.

Methods for removing one or more contaminants from an aqueous stream comprising: adding one or more hydraulic binders and one or more promoters to the aqueous stream, and separating the contaminants from the aqueous stream are provided. The methods may be used for removing contaminants that are arsenic-based, selenium-based, cadmium-based, zinc-based, mercury-based, iron-based, chromium-based and/or phosphate-based.

The present invention entails a method of treating an ion exchange regenerant stream containing selenate and removing the selenate from the regenerant stream through an oxidation-reduction process where selenate is reduced to selenite and the selenite is adsorbed onto an adsorbent which, in one embodiment, comprises iron oxide or iron oxyhydroxide. In particular, the method includes catalytically reducing the selenate to selenite in a selenate reduction reactor by reacting iron powder with the selenate in the presence of a nickel powder, which functions as a catalyst, to form selenite which is then adsorbed onto the iron oxide or iron oxyhydroxide.

In one embodiment, a treatment system for removing dissolved contaminants (e.g., arsenic) from a contaminated fluid (e.g., water) utilizes in-situ generation of adsorption filtration media or reactive components. Corrosion materials (e.g., iron oxide complexes) that serve as the adsorption filtration media or reactive components are generated by supplying a flow of contaminated fluid, and injecting air, into a generator vessel containing pieces of an oxidizable source (e.g., zero-valent iron spheres). The pieces of the oxidizable source are agitated to release particulates of corrosion materials from their surface into solution with the contaminated fluid. Simultaneous to the ongoing generation of corrosion materials, dissolved contaminants in the contaminated fluid are adsorbed on the corrosion materials. New particulate compounds generated by adsorption of the dissolved contaminants on the corrosion materials precipitate from the solution, and are filtered out, thereby removing the contaminants, and yielding treated fluid (e.g., potable water).

Methods and systems for reducing the concentration of selenocyanate in water. In the methods and systems, water containing selenocyanate is treated an oxidant to provide oxidant-treated water, which is then contacted with a zero-valent iron treatment system comprising (a) a reactive solid comprising zero-valent iron and one or more iron oxide minerals in contact therewith and (b) ferrous iron.

A biodegradable iron-crosslinked alginate is useful as a remediation agent for environmental contaminants such as phosphate. When charged with phosphate, or other nutrients, the iron-functionalized alginate can be used as an agricultural fertilizer.

Disclosed are magnetic nanoparticles and methods of using magnetic nanoparticles for selectively removing biologics, small molecules, analytes, ions, or other molecules of interest from liquids.

A method of removing or reducing the concentration of a contaminant in wastewater. The method involves combining wastewater and an elemental iron, comprising of zero valent iron, in a tank to produce treatment water. In this method the wastewater contains a contaminant consisting of: selenate [Se(VI)], selenite [Se(IV)], selenocyanate [SeCN.sup.−1], selenide [Se(−II)], and combinations thereof. The treatment water is then agitated with mechanical mixing and air sparging to produce a treated slurry. The treated slurry is then separated into a treated water stream and a contaminate stream.

A system containing a reactor vessel including zero valent iron media, a source of a conditioning additive, a source of a reaction additive, and a process control subsystem is disclosed. A method for reducing a concentration of one or more contaminants in contaminated water including contacting zero valent iron media with a conditioning additive, contacting contaminated water with conditioned zero valent iron media, and introducing a reaction additive is also disclosed. The conditioning additive and reaction additive may each contain an aluminum salt.