title: Treatment of refractory nano-filtration reject from a tannery using Pd-catalyzed wet air oxidation.
abstract: We attempted catalytic wet air oxidation (CWAO) of nanofiltration (NF)-reject using Pd based catalyst viz., Pd/activated charcoal (AC) and PdCl2 with the objective of degradation of refractory organic pollutants. Refractory organic pollutants in NF-reject before and after WAO and CWAO were confirmed by GC-MS analysis. Experiments were conducted to investigate the effects of temperature, catalyst dosage and air partial pressure on the rate of removal of total organic carbon (TOC). The reaction kinetics can be conveniently described by considering two-stage first order kinetics. The use of Pd/AC afforded 85% TOC removal, the corresponding rate constant (k) was 2.90 ± 0.075 × 10(-3)min(-1) (Pd/AC, 100mg/L; T, 473.15K; Pair, 0.69 MPa). On the other hand, 75% TOC was removed with k=2.31 ± 0.075 × 10(-3)min(-1) using Pd(2+) catalyst (Pd(2+), 16.66 mg/L; T, 473.15K; Pair, 0.69 MPa). The observed rate of mineralization under Pd-catalyzed conditions was significantly higher than that of the uncatalyzed oxidation (41%) under the similar experimental conditions. Catalyst stability experiments were performed and TEM, SEM, XRD, Raman and XPS characterization data collected. Despite some morphological transformation of support, Pd catalyst was stable under CWAO conditions.
authors.affiliation: Department of Chemistry, Tongji University, 1239 Siping Road, Shanghai 200092, PR China.
authors.forename: Pranav K
authors.initials: PK
authors.lastname: Tripathi
authors.forename: Nageswara N
authors.initials: NN
authors.lastname: Rao
authors.forename: Chetan
authors.initials: C
authors.lastname: Chauhan
authors.forename: Girish R
authors.initials: GR
authors.lastname: Pophali
authors.forename: Sanjay M
authors.initials: SM
authors.lastname: Kashyap
authors.forename: Satish K
authors.initials: SK
authors.lastname: Lokhande
authors.forename: Lihua
authors.initials: L
authors.lastname: Gan
mesh_terms: D000388:Air; D002384:Catalysis; D002606:Charcoal / Q000737:chemistry; D005374:Filtration; D007220:Industrial Waste; D010084:Oxidation-Reduction; D010165:Palladium / Q000737:chemistry*; D013633:Tanning; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D007220:Industrial Waste; D014874:Water Pollutants, Chemical; D002606:Charcoal; D010165:Palladium
keywords: Catalytic wet air oxidation; Nanofiltration-reject; Palladium catalysts; Refractory organic pollutants; Tannery effluent