Rapid small-scale column tests for Cr(VI) removal by granular magnetite

This study evaluates the possibility of using magnetite as an adsorbent for the removal of Cr(VI) in a bed column setup under continuous flow conditions. For this purpose, granular magnetite was synthesized on a large scale and tested in both batch and rapid small-scale column experiments using reliable conditions of drinking water treatment. Column tests, which were designed to scaledown larger adsorption systems in terms of size, time and water flow, indicate a higher removal capacity compared to that observed during batch experiments with magnetite powder, reaching 9.2 mg/g at pH 6.4 before residual Cr(VI) exceeds 10 μg/L. The main parameters of this process, including pH, contact time and granular size, were also examined under similar column tests suggesting the improvement of the overall effectiveness and operation time at lower water pH, higher empty bed contact times and larger particle dimensions. © IWA Publishing 2016

Inorganic engineered nanoparticles in drinking water treatment: A critical review

This review summarizes the recent research in the field of inorganic engineered nanoparticle development with direct or potential interest for drinking water treatment. The incorporation of engineered nanoparticles into drinking water treatment technologies against the removal of heavy metals, microorganisms and organic pollutants appears as a very dynamic branch of nanotechnology. Nanoparticles owe their potential to the high specific surface area and surface reactivity compared to conventional bulk materials. Depending on the mechanism of uptake, nanoparticles can be designed to establish high selectivity against specific pollutants and provide the required efficiency for application. However, despite early encouraging results, nanoparticles meet a number of limitations to get promoted and become part of large-scale water treatment plants. The most important is their availability in the required large quantities and their efficiency to fulfil the strict regulations for drinking water consumption and environmental safety. Both deal with the particle preparation cost and the cost of treatment operation with respect to the increase in supplied water price for the consumers. Under this view, this work attempts to evaluate reported studies according to their possibility to meet the reliable requirements of water technology and also suggests an experimental approach to allow validation of tested nanoparticles. © 2016 The Royal Society of Chemistry

Adapting the use of Fe3O4 nanoparticles in large-scale water treatment facilities

Magnetite nanoparticles were produced by the chemical co-precipitation of iron sulfates at alkaline conditions and were tested as a Cr(VI) adsorbent from water. Batch adsorption experiments showed a high removal efficiency, which is maximized at pH values below 6. This behavior was also verified in a continuous flow reactor, where nanoparticles were in contact with the polluted water. In particular, using a particle concentration of 1 g/L in water containing 100 μg Cr(VI)/L, a contact time of at least 2 h was required to achieve complete removal of Cr(VI). The recovery of nanoparticles after their use was accomplished using their magnetic nature. Application of an external magnetic field at the sides of the tube in which the suspension was flowing was sufficient to completely collect the nanoparticles in the outflow of the contact reactor, thus, providing water free of Cr(VI) and a solid phase. Copyright © Materials Research Society 2014