Despite their vast industrial importance, almost all extended inorganic synthetic structures and naturally occurring minerals adopt a neutral or anionic charge. This tutorial review describes the current knowledge of inorganic materials that bear a positive charge on the host. The best-known example is the family of clays known as layered double hydroxides, and other limited examples also exist. Our research efforts have given rise to a series of new cationic inorganic materials, oxides and fluorides of heavy p-block metals. Organic-based cationic materials will also be briefly discussed. Interest in these materials is widespread, with potential applications in many areas including anionic pollutant trapping, exchange, selective catalysis, polymer hybrids and nanocomposites, and biomaterials for drug or DNA delivery.

Cationic inorganic materials for anionic pollutant trapping and catalysis.

Strategies for the removal of halides from drinking water sources, and their applicability in disinfection by-product minimisation: A critical review

Removal of boron and iodine from optoelectronic wastewater using Mg–Al (NO3) layered double hydroxide

Polymer-inorganic supramolecular nanohybrids for red, white, green, and blue applications

The adsorption of iodine onto silica coated magnetite nanoparticles (im-SCMNPs) that modified with imidazole was investigated for removal of high concentrations of iodine from wastewater. Modified silica magnetite nanoparticles showed high efficiency in removing iodine from wastewater samples. The optimum pH for iodine removal was 7.0–8.0. The adsorption capacity was evaluated using both the Langmuir and Freundlich adsorption isotherm models. The size of the produced magnetite nanoparticles was determined by X-ray diffraction analysis and scanning electron microscopy. Synthesized magnetite nanoparticles showed the high adsorption capacity and would be a good method to increase adsorption efficiency for the removal of iodine in a wastewater treatment process. The Langmuir adsorption capacity (qmax) was found to be 140.84 mg/g of the adsorbent.

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Application of Modified Silica Coated Magnetite Nanoparticles for Removal of Iodine from Water Samples

From leaching experiments with metallic uranium-aluminium material test reactor fuel elements in repository-relevant MgCl2-rich salt brines, a Mg-Al-layered double hydroxide with chloride as interlayer anion was identified as a crystalline secondary phase component. In the present study, this Mg-Al-Cl-layered double hydroxide (Mg-Al-Cl-LDH) was synthesized and its ability to adsorb iodine was evaluated. The adsorption of I− was rapid, and equilibrium for an initial concentration of 4.25 × 10−5 mole/l was obtained within 48 h. Further results indicated that the adsorption isotherm for I− retention could be fitted to Freundlich and Dubinin-Radushkevich equations. The values obtained indicate that iodine is adsorbed on Mg-Al-Cl-LDH by an anion-exchange process. The adsorption of I− was also studied as a function of pH. In the pH range between 3.5 and 8.5, the adsorption was independent of the pH. The effects of competiting anions were investigated using an MgCl2-solution instead of water, and indicate that chloride anions have a greater affinity towards the Mg-Al-Cl-layered double hydroxide than iodine.

Z. Kattilparampil

Papers

Sorption of iodine on Mg-Al-layered double hydroxide