Efficient artificial mineralization route to decontaminate Arsenic(III) polluted water -the Tooeleite Way

Increasing exposure to arsenic (As) contaminated ground water is a great threat to humanity. Suitable technology for As immobilization and removal from water, especially for As(III) than As(V), is not available yet. However, it is known that As(III) is more toxic than As(V) and most groundwater aquifers, particularly the Gangetic basin in India, is alarmingly contaminated with it. In search of a viable solution here, we took a cue from the natural mineralization of Tooeleite, a mineral containing Fe(III) and As(III)ions, grown under acidic condition, in presence of SO42- ions. Complying to this natural process, we could grow and separate Tooeleite-like templates from Fe(III) and As(III) containing water at overall circumneutral pH and in absence of SO42- ions by using highly polar Zn-only ends of wurtzite ZnS nanorods as insoluble nano-acidic-surfaces. The central idea here is to exploit these insoluble nano-acidic-surfaces (called as INAS in the manuscript) as nucleation centres for Tooeleite growth while keeping the overall pH of the aqueous media neutral. Therefore, we propose a novel method of artificial mineralization of As(III) by mimicking a natural process at nanoscale

Coagulating and flocculating ferrihydrite: application of zinc acetate salt

This paper outlines a method of extraction of iron from water in the form of iron oxyhydroxide natural nanoclusters at comparatively low concentrations and varied ranges of pH using zinc acetate salt. The zinc acetate salt dissociates into Zn(2+)and acetate ions in water where Zn(2+)interacts with iron clusters present in a solution of a given iron concentration and pH, while the acetate ion helps in charge-neutralization based coagulation and consequent precipitation of such nanoclusters. The Zn(2+)ions may also lead to the growth of layered zinc hydroxide (LZH) nanosurfaces at pH >= 6 at sufficient loading. The advantage of this method is the active chemical interaction of Zn(2+)with Fe clusters, followed by growth, which ensures that only some added Zn ions remain in the water while the rest precipitate out along with the residual iron oxyhydroxide, especially at higher pH. The solid that precipitated under various different conditions was successfully evaluated by XRD (formation of ferrihydrite-like nanoclusters (n-Fh)), FTIR (the presence of acetate in the solid n-Fh), TEM (the presence of zinc at higher pH), and EXAFS (local structural characterization). ICP analysis of the obtained solid and the corresponding filtrate revealed the removal efficiency of iron and zinc from the solution at various initial concentrations and pH values. This method of extracting soluble Fh-like nanoclusters by charge neutralization appears to be a suitable promising tool for water purification, because ferrihydrite is capable of isolating other adsorbed contaminants from water, along with itself