Treatment of refractory organics from membrane rejects using ozonation.

The reject water or retentate generated from membrane application for recovery of water from tannery wastewater treatment contains certain refractory organics. These refractory organics are present in substantial quantity in the condensate of reject water also. Hence the treatment of rejects using conventional methods is rather difficult. In this paper, an attempt has been made to treat the reject water from the reverse osmosis (RO) and nano filtration (NF) operation on tannery wastewater using ozonation treatment technique. Ozonation studies on RO and NF rejects indicate that ozone dose of 80 and 100mg/min for 60 and 70 min contact time achieves 59 and 78% chemical oxygen demand (COD) reduction, respectively. The mass balance in ozone indicates the ozone consumption for RO and NF rejects varies from 2.4 to 3.4 and 2.8 to 4.5 g/g of COD removed respectively. The results suggest that ozonation of RO and NF rejects would significantly reduce the refractory organic pollutant loading into the environment from wastewater reuse facility.

Sol-gel synthesized semiconducting LaCo0.8Fe0.2O3-based powder for thick film NH3 gas sensor.

Perovskite type LaCo(x)Fe(1-x)O(3) nanoparticles was synthesized by a sol-gel citrate method. The structural, electrical and sensing characteristics of the LaCo(x)Fe(1-x)O(3) system were investigated. The structural characteristics were performed by using X-ray diffraction (XRD) and transmission electron microscopy (TEM) to examine the phase and morphology of the resultant powder. The XRD pattern shows nanocrystalline solid solution of LaCo(x)Fe(1-x)O(3) with perovskite phase. Electrical properties of synthesized nanoparticles are studied by DC conductivity measurement. The sensor shows high response towards ammonia gas in spite of other reducing gases when x=0.8. The effect of 0.3 wt.% Pd-doped LaCo(0.8)Fe(0.2)O(3) on the response and a recovery time was also addressed.

H2S sensing properties of nanocrystalline Sr2Fe(0.6)Ni(0.4)MoO6 thick film prepared by sol-gel citrate method.

Nanocrystalline Sr(2)FeMoO(6) (SFMO) belonging to the group of double perovskite oxides, was prepared by the sol-gel citrate method. The structural and microstructural characterization has been carried out with the help of X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. XRD of Sr(2)Fe(1-x)Ni(x)MoO(6) (SFNMO) shows the formation of solid solution with average grain size of about 40nm. A comparative study of gas sensing behaviour of Sr(2)FeMoO(6) and Sr(2)Fe(1-x)Ni(x)MoO(6) with reducing gases like hydrogen sulfide (H(2)S), liquid petroleum gas (LPG), hydrogen (H(2)), ethanol (C(2)H(5)OH) and carbon monoxide (CO) were also discussed. The sensitivity is calculated by measuring the change the resistance of the sensor material in the presence of gas. Among the different composition of x (x=0.2, 0.3, 0.4, 0.5), Sr(2)Fe(0.6)Ni(0.4)MoO(6) (x=0.4) shows better response to H(2)S gas at 260 degrees C. Incorporation of palladium (Pd) improves the gas response, selectivity, response time and reduced the operating temperature from 260 to 220 degrees C for H(2)S gas.