Removal and speciation of chromium by static step-by-step deposition and extraction technique

A schematic diagram of static (SbS-DET) •Static step-by-step deposition and extraction technique.•Efficient, rapid and low cost treatment of chromium species.•Cr(III) was highly removed as Cr(III)(8HQ)3 in pH⩾5.0.•Cr(VI) was completely removed as (8HQH+)2CrO42- in pH⩽2.0.•All experimental factors were optimized. Nowadays, numerous well known methods and techniques are commonly used for removal, extraction, preconcentration and speciation of chromium ions. The present work describes a continuation of our efforts to establish the novel static step-by-step deposition and extraction technique (SbS-DET) as an efficient, rapid and low cost methodology for treatment of chromium. Cr(III) and Cr(VI) were efficiently removed from aqueous and nonaqueous matrices by using the static (SbS-DET) technique. The extraction process was initiated by an initial deposition step of 8-hydroxyquinoline (8HQ) from ethanolic solution on the surface of a glass substrate. The deposited 8HQ molecules were then immersed into aqueous solution of either Cr(III) or Cr(VI) and allowed to react for the formation and deposition of Cr(III)(8HQ)3 complex and (8HQH+)2CrO42- product on the same glass substrate. The final chromium ion concentration of the examined species was substantially decreased and this process was repeated several times to ensure complete recovery and removal of the target chromium ion. Several experimental parameters were found to exhibit significant contributions to the static (SbS-DET) such as solution pH, deposition area, reaction temperature, dipping cycles, dipping time and metal ion concentration. These factors were extensively investigated, optimized and evaluated in this work. The proposed methodology (SbS-DET) was successfully applied for adsorptive removal and speciation of Cr(III) and Cr(VI) from aqueous and nonaqueous samples.