| A novel catalyst Co (C3H6NS2)3·C6H12N2S3 has been synthesized with Tetramethyl Thiuram Monosulfide and cobalt (Ⅱ) slowly evaporating at room temperature, which is an in-situ reaction. Its structure also has been characterized by single crystal X-ray diffraction(XRD),Infrared spectrum (IR) and CNH elemental analysis. The catalyst crystallizes in P-1 space group with one Cobalt (Ⅲ) ion, three new ligands and one dissociated TMTM molecule in the asymmetric unit, presenting a distorted octahedral geometry.Using the single crystal heterogeneous Fenton catalytic degradation of Direct Orchid 6 and Direct Green 28, as a model reaction, the results showed that the degradation and mineralization rate of Direct Orchid 6 and Direct Green 28 reached a fairly high level under UV-light or microwave irradiation whether wastewater in acidic condition or alkaline condition. After the Fenton reaction the single crystal could be repeatedly used, which reduce the cost of wastewater treatment and secondary pollution.Though Direct Orchid 6 and Direct Green 28 could be adsorbed by the single crystal catalyst, the adsorption was not strong. The absorption of the dye enhanced with pH value increase. Both of the maximum absorptions are 6.33% and 5.99%, respectively, under 450W mercury lamp irradiation after 90 min in the extension of pH value. While the maximum absorptions are 5.17% and 4.86%, respectively, under microwave irradiation after 10 min among the pH ranges. Compared to UV-light irradiation the absorption under microwave irradiation was weak.Four major influencing factors of heterogeneous Fenton catalytic degradation of dyes are the pH value of waster water, the dosage of catalyst, the initial concentration of dyes and the dosage of H2O2, which have been respectively discussed by single factor method and Orthodoxy experimentation in order to find the optimality conditions of wastewater degradation.Under UV-irradiation the optimality conditions of degradation of Direct Orchid 6 are as follows: in acidic condition, the pH value of wastewater is 3.0, the dosage of catalyst is 1200mg·L-1, the initial concentration of dyes is 50mg·L-1 and the dosage of H2O2 is 800μL/L; In alkaline condition, the pH value of wastewater is 10.0, the dosage of catalyst is 1600mg·L-1, the initial concentration of dyes is 10mg·L-1 and the dosage of H2O2 is 800μL/L. The optimality conditions of degradation of Direct Orchid 28 are as follows: in acidic condition, the pH value of waster water is 3.0, the dosage of catalyst is 1600mg·L-1, the initial concentration of dyes is 100mg·L-1 and the dosage of H2O2 is 1000μL/L; In alkaline condition, the pH value of wastewater is 10.0, the dosage of catalyst is 1200mg·L-1, the initial concentration of dyes is 50mg·L-1 and the dosage of H2O2 is 1000μL/L.For two dyes Under UV-irradiation, pH value of wastewater is the most influence factor, the second is the dosage of catalyst, the third is the dosage of H2O2 and the last is the initial concentration of dyes.Under microwave irradiation, for Direct Orchid 6, the first is the pH value of wastewater, the second is the dosage of catalyst, the third is the dosage of H2O2 and the last is the initial concentration of dyes. The optimality conditions of degradation of Direct Orchid 6 under microwave irradiation are the pH value of waster water 3.0, the dosage of catalyst 400mg·L-1, the initial concentration of dyes 50mg·L-1 and the dosage of H2O2 800μL/L; or the pH value of waster water 10.0, the dosage of catalyst 600mg·L-1, the initial concentration of dyes 50mg·L-1 and the dosage of H2O2 800μL/L.For Direct Green 28, in acidic condition, the first is the pH value of wastewater, the second is the dosage of catalyst, the third is the dosage of H2O2 and the last is the initial concentration of dyes, which is the same to the system of Direct Orchid 6. Under microwave irradiation, the optimality conditions of degradation of Direct Orchid 6 are the pH value of waster water 3.0, the dosage of catalyst 600mg·L-1, the initial concentration of dyes 100mg·L-1 and the dosage of H2O2 1000μL/L. In alkaline condition, the first influencing factor is the pH value of wastewater, the second is the dosage of H2O2, the third is the dosage of catalyst and the last is the initial concentration of dyes. The optimality degradation experiment conditions of Direct Green 28, under microwave irradiation, is the pH value of wastewater 10.0, the dosage of catalyst 600mg·L-1, the initial concentration of dyes 10mg·L-1 and the dosage of H2O2 1000μL/L.The photo-catalytic degradation of Direct Orchid 6 and Direct Green 28 has been experimentally demonstrated to follow the Langmuir-Hinshelwood kinetic model when reaction was proceeding under UV-irradiation for 10 minute. When pH value is 3.0, the Linear relations of Direct Orchid 6 and Direct Green 28 are that y=18.912x + 0.0131 (R2=1) and y=20.947x + 0.0056 (R2=0.9999);Meanwhile the reaction rate constants (0.76×102 and 1.79×102 mg(L·min)-1) and the adsorption constants (6.93×10-4 and 2.64×10-4 7.23×10-5L·mg-1) have been determined, respectively. When pH value is 10.0, the Linear relations of Direct Orchid 6 and Direct Green 28 are that y=21.758x– 0.0033 (R2=1) and y=22.122x– 0.0016 (R2=0.9999); meanwhile the reaction rate constants(3.03×102 and 6.25×102mg(L·min)-1) and the adsorption constants(1.52×10-4 and 7.23×10-5L·mg-1)have also been determined, respectively.The catalytic degradation of two type dyes under microwave has been also discussed. The microwave-catalytic degradation of two type dyes has been experimentally demonstrated to follow pseudo-first order kinetic process in the previous 10 minutes.
|
PDF Full Text Request