Enhanced Cr(Ⅲ) Removal From Water By A Novel Hydrous Zirconium Oxide Loaded Nanocomposite

Chromium is a kind of heavy metal which has adverse effect to ecology, environment and human beings. Therefore, many countries and regions have already established very strict treatment and emission standard for wastewater containing chromium. Generally speaking, Cr(Ⅵ) is more toxic than Cr(Ⅲ). While as people know more about the toxicity of Cr(Ⅲ), as well as the transformation mechanism between Cr(Ⅲ) and Cr(VI), an advanced treatment is increasingly needed for water containing Cr(Ⅲ). The main source of Cr(Ⅲ) in environment is the wastewater of electroplate and tannery, and the common treatment cannot get an advanced management to this kind of water. A promising solution for this challenge task is to develop new environmental-friendly materials which have selective adsorption toward Cr(Ⅲ).Hydrated zirconium oxide (HZO) is a kind of amphoteric compound with a high capacity of inorganic ions. In this study, we fabricated some amorphous HZO with precipitation method. The ICP result shows that the Zr content in it is about 51.5% and water content is 25% as TGA indicates. The particle size of HZO in water distributes mainly in two different sectors,70% of them are about 0.2μm, and others are in 1-10 μm sector. The specific area and mean pore size are 248.1 m2/g and 2.82 nm respectively. Study shows that as the pH increases in solution, the Cr(Ⅲ) adsorption capacity of HZO improves; coexisted anions will promote the Cr(Ⅲ) adsorption capacity while cations has no obvious impact to the Cr(Ⅲ) adsorption of HZO.Meantime, a new kind of nanocomposite material (HZO-001) in which HZO was used as a precursor was fabricated too. This circular nanocomposite has a specific area about 21.6 m2/g, and the mean pore size is 24.8 nm. Zr content in the composite is 16.2%.Our study suggests the coexisted anions will promote the Cr(Ⅲ) adsorption capacity of HZO-001; although cations with one positive charge has no effect to the adsorption of HZO-001, cations like Ca2+ and Mg2+ can inhibit Cr(Ⅲ) adsorbed by HZO-001. As to the HZO-001 which has saturated adsorbed Cr(III), a di-solution of HNO3(pH=1) with 10% Ca(NO3)2 has been used for its desorption, followed by a regeneration process with a mixed solution of NaCl and NaOH. Fixed bed experiment indicates that the treatment ability of HZO-001 to wastewater which has a initial Cr(III) concentration about 5 mg/L is larger than 3400 BV. Recycling experiment suggested no obvious HZO loss of HZO-001 in its utility, thus HZO-001 can be a promising material in treatment of wastewater containing Cr(III).