Providing safe drinking water is a great challenge for both the developing and the developed world. Increasing demand and source water quality deterioration has led to the exploration of new technological innovations for better water management. Nanotechnology holds great promise in ensuring safe drinking water through designing innovative centralised and decentralised (household-level) water treatment systems. The paper provides an overview of recent advances in nanotechnologies for (household level) water treatment processes, such as its use as nanoadsorbents, photocatalysts, microbial disinfectants and in membranes. Extensive implementation of nanotechnology for water treatment would require overcoming the high cost of the nanomaterials by enabling their reuse and regeneration. This would also ensure minimising potential environmental exposure. Potential advances in nanotechnology must go hand in hand with environmental health to alleviate any undesirable consequences to humans.

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The study was designed to synthesize iron oxide/alumina nanocomposites and to investigate their application as an adsorbent to remove both fluoride and arsenic from aqueous solutions. The nanocomposites were extensively characterized by X-ray diffraction analysis, Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy and zeta potential analysis. The size and morphology of the particles were determined by scanning electron microscopy which revealed an average particle size of ~230 nm. The synthesized nanocomposites were stable for at least 4 h in static conditions as evidenced by particle size measurements. Batch sorption studies were carried out and sorption isotherms and reaction kinetics were analyzed. The nanocomposites followed the Langmuir isotherm model and fitted well with pseudo-second-order reaction for both As and F. The maximum sorption capacity of the nanocomposites for As(III), As(V) and F at pH 7 was 1,136 µg/g, 2,513 µg/g and 4 mg/g, respectively. The presence of F in the model water had a synergistic effect on As(III) and As(V) removal whereas the presence of As had no significant effect on F removal at pH 7. Furthermore, the nanocomposites demonstrated significant antibacterial activity at a concentration of 4 mg/mL with ~3 log reduction of Escherichia coli after 24 h. The results of the study showed that the synthesized nanocomposites can be a promising adsorbents for As and F removal in small-scale water systems.

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The study was designed to synthesize iron oxide nanoparticles and to investigate their application as a sorbent to remove fluoride and arsenic from contaminated water. The nanoparticles, synthesized by co-precipitation, were extensively characterized by X-ray diffraction analysis, Brunauer-EmmettTeller analysis and zeta potential analysis. The size and morphology of the particles were determined by scanning electron microscopy, which revealed an average particle size of ~130 nm. The synthesized nanoparticles were stable for at least 4 h in static conditions as evidenced by particle size measurements. Batch sorption studies were carried out, and sorption isotherms and reaction kinetics were analyzed. The iron oxide nanoparticles were not effective in fluoride removal at the pH and concentrations studied. They followed the Freundlich isotherm model and fitted well with pseudo-first-order reaction for As(III) and As(V) with R2 value of 0.93 and 0.98 at pH 7, respectively. The maximum sorption capacity of the nanoparticles for As(III) and As(V) at pH 7 were 909 and 3,333 µg/g, respectively. The results of the study showed that the synthesized nanoparticles can be promising adsorbents for As removal in small-scale water systems.@en

The study was designed to optimize the process for the synthesis of alumina/iron oxide nanocomposites and to investigate their potential as a sorbent to remove fluoride and arsenic from contaminated water. The nanocomposites had a size range between ∼250-500 nm. Process variables such as the weight of iron oxide nanoparticles added during the course of synthesis of the nanocomposites and the duration of calcination were studied as a function of particle size and As and F removal potential. Increase in the weight of iron oxide nanoparticles (from 0.05 g to 0.1 g) added during the course of synthesis did not lead to a significant change in the particle size measurements nor did it increase the As and F removal capacity. Increase in the duration of calcination at 550 °C led to a corresponding increase in the particle size from 219 ± 13.31 nm to 273 ± 19.49 nm. The sorption data for As (III), As (V) fitted best to Freundlich isotherm while for F it fitted the Langmuir isotherm. Increase in the duration of calcination from lh to 3h showed increased qm values for As (V) and F. The results demonstrated that 0.05 g of iron oxide nanoparticles added during synthesis and calcination of the composites at 550 °C/3h was sufficient for optimum As and F removal.@en

The study provides a comparative analysis of As (III), As (V) and F removal by iron oxide nanoparticles and iron oxide/alumina nanocomposites. The nanoparticles were characterized by particle size, zeta potential and Scanning Electron Microscopic analysis which showed spherical iron oxide nanoparticles around ~200 nm and nanocomposites around ~300 nm. Batch sorption studies carried out at varying initial concentrations of As and F revealed an enhanced F and As sorption capacity for the nanocomposites. The sorption isotherm showed that the data for As (III), As (V) and F fitted best to Freundlich isotherm for both the type of nanoparticles. The maximum sorption capacity of the iron oxide nanoparticles for As (III) and As (V) at pH 7 were 909 μg/g and 3333 μg/g while the comparative qm values for the nanocomposites were 1000 μg/g and 2500 μg/g respectively. The maximum F sorption capacity of iron oxide nanoparticles was 1.47 mg/g while it was 4.82 mg/g for the nanocomposites. The preliminary results of the study showed that the nanocomposites can be promising adsorbents for both As and F removal in small scale water systems.

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