Cr(VI) removal from a synthetic solution using a novel carbonaceous material prepared from oily sludge of tank bottom.

A novel carbonaceous material (NCM), prepared by the pyrolyzation of the oily sludge of tank bottom, was proposed to remove Cr(VI) from a synthetic solution for the first time. The effects of initial Cr(VI) concentration, NCM dosage and initial solution pH on Cr(VI) removal and the adsorption kinetics, the adsorption isothem were investigated. The removal mechanism was studied by comparing the surface properties of NCM before and after the Cr(VI) removal. The results showed that NCM can effectively remove Cr(Ⅵ) from the synthetic solution with the increase of solution pH at equilibrium. At the initial Cr(Ⅵ) concentrations of 40, 100, 150 and 250 mg/L and NCM dosages of 1, 3, 6 and 8 g/L with initial solution pH of 2, the removal efficiency of Cr(VI) was 95.5, 96.8, 95.2 and 81.2%, and the solution pH at equilibrium reached 2.3, 3.5, 5.8 and 7.5, respectively. NCM was suitable for Cr(Ⅵ) removal while the initial Cr(VI) concentration was less than 100 mg/L and initial solution pH was lower than 2.5. Most of Cr(VI) was removed by the reduction of Fe2+ and S2- in NCM to Cr(III) and with the generation of stable FeCr2O4. Some Cr(VI) may be removed by reacting with Fe2+ and Ca2+ to produce CaCrO4 and FeCrO4 on the NCM surface. The dissolution of CaAl2Si2O8 and CaS in the solution increased the solution pH at equilibrium. NCM has been proved to be a material with dual functions both chemical reduction and adsorption.

Sol gel synthesis of hybrid chitosan/calcium aluminosilicate nanocomposite membranes and its application as support for CO2 sensor.

Modification of chitosan with cross-linkers, blends with various kinds of polymers, nanoparticles and new organic-inorganic hybrid composites in order to obtain some improved properties attached more attention nowadays due to their good sensitivity in changing electrical and optical properties. In the current work modified hybrid chitosan/calcium aluminosilicate (CH/CAS) nanocomposite membranes and doped with (3, 5 & 7 mol%) Al2O3 nanoparticles were synthesized via sol-gel process in acidic conditions, which can be efficiently employed to capture CO2 gas at lower and moderate temperatures. Furthermore, the fabricated CH/CAS nanocomposite membrane loading with (3, 5 & 7 mol%) Al2O3 were investigated using XRD, SEM, FTIR and dielectric measurements. The results indicated that the incorporation of Al2O3 in CH/CAS matrix significantly affected on the structural, dielectric and appeared good reliability for sensing CO2 at atmospheric pressure. The dielectric behaviour for the prepared CH/CAS indicates that the dielectric constant (ε') decreases. According to XRD the introducing of Al2O3 leads to increase the crystallinity of the system and thus the dipoles of the system orient hardly with the applied field and results in lesser dielectric constant (ε'). Correspondingly, the CH/CAS nanocomposite membranes were characterized and its performance as CO2 gas sensor was evaluated.