A facile, versatile approach to hydroxyl-anchored metal oxides with high Cr(VI) adsorption performance in water treatment

In this study, a facile and versatile urea-assisted approach was proposed to synthesize Chinese rose-like NiO, pinecone-like ZnO and sponge-like CoO adsorbents. The presence of urea during syntheses endowed these adsorbents with high concentration of surface hydroxyl groups, which was estimated as 1.83, 1.32 and 4.19 mmol [OH^-] g^-1 for NiO, ZnO and CoO adsorbents, respectively. These surface hydroxyl groups would facilitate the adsorption of Cr(vi) species (e.g. HCrO₄^-, Cr₂O₇^2- and CrO₄^2-) from wastewater by exchanging with hydroxyl protons or hydroxide ions, and hence result in extremely high maximum adsorbed amounts of Cr(vi), being 2974, 14 256 and 408 mg g^-1 for NiO, ZnO and CoO adsorbents in the pH range of 5.02-5.66 at 298 K, respectively. More strikingly, the maximum adsorbed amounts of Cr(vi) would be greatly enhanced as the adsorbing temperature is increased, and even amount to 23 411 mg g^-1 for ZnO adsorbents at 323 K. Based on the kinetics and equilibrium studies of adsorptive removal of Cr(vi) from wastewater, our synthetic route will greatly improve the adsorptivity of the as-synthesized metal-oxide adsorbents, and hence it will shed new light on the development of high-performance adsorbents.

Activated charcoal mediated purification of Yellow Sodium Sulphate: a green process to utilize a hazardous by-product of the leather chemical industry

Activated charcoal assisted a green and sustainable recovery of highly pure sodium sulphate and Cr-residue from yellow sodium sulphate, a hazardous by-product of the leather chemical industry.

Gram-grade Cr(vi) adsorption on magnetite/carbon hybrid architectures

The maximum Cr(vi) adsorption capacities on our as-synthesized Fe₃O₄@C architectures were found to be ca. 1100 mg g⁻¹.