Shri Chand

Catalytic wet peroxide oxidation of azo dye (Congo red) using modified Y zeolite as catalyst

The present study explores the degradation of azo dye (Congo red) by catalytic wet peroxide oxidation using Fe exchanged commercial Y zeolite as a catalyst. The effects of various operating parameters like temperature, initial pH, hydrogen peroxide concentration and catalyst loading on the removal of dye, color and COD from an aqueous solution were studied at atmospheric pressure. The percent removals of dye, color and COD at optimum pH(0) 7, 90 degrees C using 0.6 ml H(2)O(2)/350 ml solution and 1g/l catalyst was 97% (in 4h), 100% (in 45 min) and 58% (in 4h), respectively. The % dye removal has been found to be less in comparison to % color removal at all conditions, e.g. dye removal in 45 min and at above conditions was 82%, whereas the color removal was 100%. The results indicate that the Fe exchanged Y zeolite is a promising catalyst for dye removal. Fe exchanged catalyst is characterized using XRD, SEM/EDAX, surface area analyzer and FTIR. Though the dye, color and COD removals were maximum at pH(0) 2 but as the leaching of Fe from the catalyst was more in acidic pH range, pH(0) 7 was taken as operating pH due to almost comparable removals as of pH(0) 2 and no leaching of Fe ions.

Zeolite-encapsulated Cr(III), Fe(III), Ni(II), Zn(II) and Bi(III) salpn complexes as catalysts for the decomposition of H2O2 and oxidation of phenol

Abstract Cr(III), Fe(III), Bi(III), Ni(II) and Zn(II) complexes of N , N′ -bis(salicylidene)propane-1,3-diamine (H 2 salpn) encapsulated in Y-zeolite were prepared by flexible ligand method. These complexes were characterized by chemical and thermal analyses, FT-IR and electronic spectral studies and their XRD pattern. The encapsulated materials are active catalysts for the decomposition of hydrogen peroxide and for the oxidation of phenol using H 2 O 2 as oxidant with good selectivity.

Spectroscopic and catalytic activity study of N, N'-bis(salicylidene)propane-1,3-diamine copper(II) encapsulated in zeolite-Y

Abstract N , N ′-Bis(salicylidene)propane-1,3-diamine copper(II), [Cu(salpn)] has been encapsulated in the super cages of zeolite-Y and characterized by spectroscopic studies and thermal as well as X-ray diffraction (XRD) patterns. Catalytic activity of [Cu(salpn)]-Y in the oxidation of phenol to a mixture of catechol and hydroquinone using H 2 O 2 as an oxidant has been studied and the best suited reaction conditions have been optimized by considering the effect of solvents used, concentration of substrate, temperature, reaction time, amount of catalyst and oxidant. Under the best suited conditions, the selectivity towards the formation of catechol and hydroquinone is about 80 and 20%, respectively.

Liquid-phase catalytic hydroxylation of phenol using Cu(II), Ni(II) and Zn(II) complexes of amidate ligand encapsulated in zeolite-Y as catalysts

Copper(II), nickel(II) and zinc(II) complexes of amidate ligand 1,2-bis(2-hydroxybenzamido)ethane(H2hybe) encapsulated in the super cages of zeolite-Y have been prepared and characterized by spectroscopic studies and thermal as well as X-ray diffraction (XRD) patterns. These complexes catalyze the liquid-phase hydroxylation of phenol with H2O2 to catechol as a major product and hydroquinone as a minor product. Considering the concentration of substrate and oxidant, amount of catalyst, temperature of the reaction and volume of solvent, a best-suited reaction condition has been optimized to get maximum hydroxylation. Under the optimized reaction conditions, [Cu(hybe)]-Y has shown the highest conversion of 40% after 6 h, which is followed by [Ni(hybe)]-Y with 37% conversion and [Zn(hybe)]-Y has shown the poorest performance with 33% conversion. All these catalysts are more selective towards catechol formation (∼90%), irrespective of their catalytic performance.

REACTIVE EXTRACTION OF PROPIONIC ACID USING TRI-n-OCTYLAMINE

Reactive extraction of propionic acid using tri-n-octylamine (TOA) in 1-decanol and 2-octanol was studied. Physical and chemical extractions from aqueous solution of acid were presented. The extraction of propionic acid from aqueous solutions using TOA in 1-decanol and 2-octanol, respectively, resulted in a degree of extraction as high as 92%. The effect of temperature was studied and it was found that as the temperature was raised from 305 to 353 K, KE decreased from 30.11 to 11.85 and 19.44 to 10.23 in the case of 30 and 40% TOA, respectively, in 1-decanol and 28.57 to 11.32 and 21.99 to 8.70 in the case of 30 and 40% TOA, respectively, in 2-octanol. TOA in both diluents was found to be more effective at pH values less than 4. Increasing the pH from natural pH to 7 was found to severely affect the extraction. Different salts (NaCl, Na2SO4, K2HPO4) and substrate sources (lactose and dextrose) were selected to study their effects on the reactive extraction of propionic acid. The presence of salts lowers the extraction, but substrate sources were found to have no effect on the extraction of propionic acid using TOA in either diluent. Six model solutions were prepared containing various concentrations of salts and substrate to get a real view of extraction. Extraction from the model solutions was lower than that observed in the aqueous solutions. However, the values are still high enough to have a sustainable extraction.

Effectiveness of coagulation and acid precipitation processes for the pre-treatment of diluted black liquor

The effectiveness of coagulation (using aluminium-based chemicals and ferrous sulfate) and acid precipitation (using H(2)SO(4)) processes for the pre-treatment of diluted black liquor obtained from a pulp and paper mill is reported. Commercial alum was found to be the most economical among all the aluminium and ferrous salts used as a coagulant. A maximum removal of chemical oxygen demand (COD) (ca. 63%) and colour reduction (ca. 90%) from the wastewater (COD = 7000 mg l(-1)) at pH 5.0 was obtained with alum. During the acid precipitation process, at pH < 5.0, significant COD reductions (up to 64%) were observed. Solid residue obtained from the alum treatment at a temperature of 95 degrees C showed much better (3 times) settling rate than that for the residue obtained after treatment with the same coagulant at a temperature of 25 degrees C. The settling curves had three parts, namely, hindered, transition and compression zones. Tory plots were used to determine the critical height of suspension-supernatant interface that is used in the design of a clarifier-thickener unit. High heating values and large biomass fraction of the solid residues can encourage the fuel users to use this waste derived sludge as a potential renewable energy source.

Treatment of paper and pulp mill effluent by coagulation.

Pulp and paper mill effluent is highly polluting and is a subject of great environmental concern. In the present research we studied the removal of chemical oxygen demand (COD) and colour from paper mill effluent, using the coagulation process. A batch coagulation study was conducted using various coagulants such as aluminium chloride (AlCl3), polyaluminium chloride (PAC) and copper sulphate (CuSO4·5H20). The initial pH of the effluent had a tremendous effect on the COD and colour removal. The PAC reduced COD by 83% and reduced colour by 92% at an optimum pH of 5.0 and a coagulant dose of 8 mL L−1. With AlCl3, at an optimum pH of 4.0 and a coagulant dose of 5 g L−1, 72% COD removal and 84% colour removal were observed. At an optimum pH of 6.0 and a mass loading of 5 g L−1, 76% COD reduction and 78% colour reduction were obtained with copper sulphate. It was also observed that, after addition of coagulant, the pH of the effluent decreased. The decrease in the pH was highest with AlCl3, followed by PAC and then CuSO4·5H20.

Treatment of desizing wastewater by catalytic thermal treatment and coagulation.

In the present study, the coagulation of the fresh and thermally treated desizing wastewater has been reported. The maximum COD reduction of fresh desizing wastewater using coagulation was observed with commercial alum at initial pH 4. This was followed by aluminum potassium sulfate (pH 4), FeCl(3) (pH 6), PAC (pH 6) and FeSO(4) (pH 4). The maximum COD reduction observed at a coagulant (commercial alum) dose of 5 kg/m(3) and pH 4 was 58% whereas the color reduction at these conditions was 85%. The results reveal that the application of coagulation on the catalytic thermal treated effluent is more effective in removing nearly 88% of COD and 96% of color at above mentioned conditions except at a coagulant dose of 1 kg/m(3). The amount of inorganic sludge generated gets drastically reduced (almost 25%) due to the reduced amount of coagulant. The COD and color of the final effluent were found to be 98.6 mg/l and 2.67 PCU, respectively, and the COD/BOD(3) ratio was 1.36. The settling rate of the slurry was found to be strongly influenced by treatment pH. The slurry obtained after treatment at pH 12 settled faster in comparison to slurry obtained at pH 4. The filterability of the treated effluent is also strongly dependent on pH. pH 12 was adjudged to be the best in giving highest filtration rate.

Adsorption of lead from aqueous solution onto coir-pith activated carbon

Abstract Adsorption of lead (Pb(II)) from aqueous solution using H2SO4-activated carbon developed from coir pith (CPAC) was studied. Batch experiments were performed to explain the effect of initial pH (pH 0), contact time, adsorbent dose, and temperature on adsorption. A pH 0 of 5.0, a dose of 1 g L−1 for adsorption at a concentration of Pb of 20 mg L−1 were the optimal conditions. The adsorption of lead onto CPAC was found to be a gradual process and the quasi-equilibrium condition reached in 4 h. The adsorption followed pseudo-second-order kinetics and the adsorption equilibrium followed the Temkin isotherm. Thermodynamic parameters such as ΔG 0, ΔH 0, and ΔS 0 were evaluated by applying the Arrhenius and Van’t Hoff equations, and it was found that adsorption of Pb(II) on CPAC was spontaneous and endothermic.

Oxidation of styrene and cyclohexene with TBHP catalyzed by copper(II) complex encapsulated in zeolite-Y

Reaction of monobasic tridentate Hacpy-oap (Hacpy-oap = Schiff base derived from 2-acetylpyridine and o-aminophenol) with CuIICl2 in refluxing methanol results in formation of [CuII(acpy-oap)Cl]. DFT calculations have been used to optimize structure of the complex. [CuII(acpy-oap)Cl] has also been encapsulated in the nanocavity of zeolite-Y and its encapsulation ensured by various physico-chemical techniques. Neat as well as encapsulated complexes are active catalysts for oxidation of styrene and cyclohexene using tert-butylhydroperoxide. Reaction conditions for oxidation of these substrates have been optimized by concentration of oxidant, amount of catalyst, volume of solvent and temperature of the reaction mixture. [CuII(acpy-oap)Cl] does not leach metal ion during catalytic activity and is recyclable.