Degradation Of H-acid Research Articles

Kinetics and mechanism study of H-acid degradation by peroxymonosulfate activation with Co3O4-Fe2O3/Al2O3

Alumina supported bimetallic cobalt-iron oxide (Co3O4-Fe2O3/Al2O3) catalyst was prepared via co-impregnation of boehmite with the mixture solution of cobalt nitrate and iron nitrate followed by calcination in air. X-ray photoelectron spectroscopy and high-resolution transmission electron microscope analyses confirmed the existence of highly dispersed Co3O4 and Fe2O3 nanoparticles in the as-prepared catalysts. The catalytic activity of Co3O4-Fe2O3/Al2O3 was evaluated for the degradation of H-acid in aqueous solution by heterogeneous activation of peroxymonosulfate. The results indicated that the Co3O4-Fe2O3/Al2O3 catalyst exhibited an identical initial activity but much better recyclability than Co3O4/Al2O3 due to its low amount of metal leaching and possible redox circle of Co(II)/Co(III). Electron paramagnetic resonance spectroscopy and radical quenching experiments suggested that singlet oxygen (1O2) contributed much more than ·OH and SO4• to H-acid degradation, and the degradation mainly followed a nonradical reaction mechanism.

Influence of Fenton's reagent doses on the degradation and mineralization of H-acid

The recalcitrant H-acid (1-amino-8-naphthol-3,6-disulfonic acid) in aqueous solution was oxidized by Fenton process, focusing on the relation of Fenton's reagent doses and degradation products. The experimental results showed that COD and TOC removals and biodegradability (BOD/COD ratio) of the solution increased with increasing Fenton's reagent doses. Over 80% COD can be removed and the biodegradability was improved significantly. It was found that major SO3H and NH2 groups in H-acid molecules were mineralized to SO42− and NH4+ ions during Fenton oxidation processes. H-acid degradation intermediates with benzene structures substituted by hydroxyl and/or carboxyl groups were identified by GC–MS. It was also found that short-chain fatty acids primarily oxalic acid were degradation products of H-acid by Fenton oxidation. Oxalic acid accumulated could account for approximately 60% of the residual TOC. The degradation pathway of H-acid was proposed based on above analyses in this work.

Application of TiO2–RuO2/Ti electrodes modified with transition metal oxides in photoelectrochemical degradation of H-acid - synergetic effect

Abstract Results of investigation of H-acid degradation in photoelectrochemical process with the application of TiO 2 –RuO 2 /Ti electrodes modified with transition metals oxides like: Nb 2 O 5 , ZrO 2 and Y 2 O 3 , are described. Comparison of H-acid conversion calculated as a change in COD and TOC in photocatalytic, electrochemical and photoelectrochemical process shows that the highest conversion was achieved in the photoelectrochemical process due to a significant synergetic effect. The synergetic effect in the photodegradation of H-acid was estimated as a parameter – synergetic factor (SF). It appeared that SF depended on current intensity applied in the photoelectrochemical degradation of H-acid and on modification of titanium electrodes. The highest synergetic effect was obtained in the case of TiO 2 –RuO 2 /Ti electrodes modified with Nb 2 O 5 in the atmosphere of nitrogen and applied in the processes carried out at the current intensity of 0.3 A.

Study on Catalytic Wet Oxidation of H-Acid Containing Water over Fe/SiO<sub>2</sub> Catalyst

This study has investigated the degradation of H-acid (1-amino-8-naphthol-3, 6-disulfonic acid) containing water by catalytic wet hydrogen peroxide oxidation method, in which the catalyst of Fe/SiO2 was prepared by impregnation technology. The effect of catalyst dosage, initial pH value, amount of hydrogen peroxide and reaction temperature on the degradation process have been discussed, and the results indicated that wet hydrogen peroxide oxidation is an effective method for treating the wastewater containing H-acid, under the conditions that: catalyst dosage was 2 g, initial pH value was 7, amount of hydrogen peroxide was 10 mL (0.83 time of theoretical required amount) and reaction temperature was 80 °C, the COD and color removal rate can reach 87.3% and 96.5%, respectively.

Degradation of h-acid by free and immobilized cells of Alcaligenes latus

Alcaligenes latus, isolated from industrial effluent, was able to grow in mineral salts medium with 50 ppm (0.15 mM) of H-acid as a sole source of carbon. Immobilization of Alcaligenes latus in Ca-alginate and polyurethane foam resulted in cells embedded in the matrices. When free cells and immobilized cells were used for biodegradation studies at concentration ranging from 100 ppm (0.3 mM) to 500 ppm (1.15 mM) degradation rate was enhanced with immobilized cells. Cells immobilized in polyurethane foam showed 100% degradation up to 350 ppm (1.05 mM) and 57% degradation at 500 ppm (1.5 mM). Degradation rate of Ca-alginate immobilized cells was less as compared to that of polyurethane foam immobilized cells. With Ca-alginate immobilized cells 100% degradation was recorded up to 200 ppm (0.6 mM) of H-acid and only 33% degradation was recorded at 500 ppm (1.5 mM) of H-acid. Spectral analysis of the products after H-acid utilization showed that the spent medium did not contain any aromatic compounds indicating H-acid degradation by A. latus.

Degradation of h-acid by free and immobilized cells of Alcaligenes latus

Alcaligenes latus, isolated from industrial effluent, was able to grow in mineral salts medium with 50 ppm (0.15 mM) of H-acid as a sole source of carbon. Immobilization of Alcaligenes latus in Ca-alginate and polyurethane foam resulted in cells embedded in the matrices. When free cells and immobilized cells were used for biodegradation studies at concentration ranging from 100 ppm (0.3 mM) to 500 ppm (1.15 mM) degradation rate was enhanced with immobilized cells. Cells immobilized in polyurethane foam showed 100% degradation up to 350 ppm (1.05 mM) and 57% degradation at 500 ppm (1.5 mM). Degradation rate of Ca-alginate immobilized cells was less as compared to that of polyurethane foam immobilized cells. With Ca-alginate immobilized cells 100% degradation was recorded up to 200 ppm (0.6 mM) of H-acid and only 33% degradation was recorded at 500 ppm (1.5 mM) of H-acid. Spectral analysis of the products after H-acid utilization showed that the spent medium did not contain any aromatic compounds indicating H-acid degradation by A. latus.

Degradation of H-acid and its derivative in aqueous solution by ionising radiation

The mechanism of high-energy radiation induced degradation of H-acid (4-amino-5-hydroxynaphthalene-2,7-disulphonic acid, ( I)) and its derivative, 4-hydroxynaphthalene-2,7-disulphonic acid ( II) (central parts of a large number of azo dyes), was investigated in aqueous solutions. These compounds can be efficiently destroyed by the OH and hydrated electron intermediates produced during water radiolysis. As the first step of degradation mainly cyclohexadienyl-type radicals form, however, with I H-atom elimination from the NH 2 group is also observed yielding anilino-type radicals. Both the cyclohexadienyl and the anilino-type radicals decay on the millisecond timescale. In the OH reactions as stable products hydroxylated molecules and quinone-type compounds form. These molecules by further decomposition of the ring structure transform to open chain molecules. In the case of hydrated electron, the primarily formed products have absorption spectra shifted to the low-wavelength region indicating the destruction of at least one of the aromatic rings.

Degradation of H-acid by combined photocatalysis and ozonation processes

The combination of TiO 2-assisted photocatalysis and ozonation (TiO 2/UV/O 3) to degrade H-acid (1-amino-8-naphthol-3,6-disulfonic acid) was investigated. It was observed that a synergistic effect occurs in this process. The effects of O 3 dosage, initial solution pH and initial concentration of H-acid on the efficiency of the process were also studied. The results showed that COD (chemical oxygen demand) removal rate increased with increasing O 3 dosage whereas initial solution pH had little effect. An H-acid solution of 500–2000 mg/L could be efficiently degraded using TiO 2/UV/O 3. The intermediates formed in the early phase of degradation were studied using UV–vis absorption spectra, IC, HPLC–MS and IR; four possible intermediates, 1-amino-5,7,8-trihydroxynaphthalene-3,6-disulfonic acid, 1-amino-2,4,5,8-tetrahydroxynaphthalene-3,6-disulfonic acid, 8-hydroxy-1,2-naphthoquinone-3,6-disulfonic acid and 8-hydroxy-1,4-naphthoquinone-3,6-disulfonic acid, were proposed.

Decomposition of a dye intermediate, (H-acid) 1 amino-8-naphthol-3,6 disulfonic acid in aqueous solution by ozonation

In this research, ozonation of H-acid, a dye intermediate was studied in a semi batch reactor. The effect of pH and ozone dose on decolorization and degradation of H-acid was studied. The results showed that pH 11.5 was effective for color and COD removal. Both color (98.7%) and COD (87.8%) could be removed by 30 min of ozonation at an ozone dose of 4.33 mg/l. Oxidation and cleavage of substituent groups were evidenced by the release of nitrate and sulphate during ozonation. The study also showed that the O 3/Fe 2+ ion influenced the ozonation efficiency of H-acid. Treatment with O 3/H 2O 2 did not enhance color and COD removal. Acetic acid and oxalic acid were identified as the major oxidation products. The ozonation reaction followed a pseudo first order kinetics. Increase in the biodegradability as measured by the BOD 5/COD ratio was observed after ozonation. The study revealed that ozonation of dye intermediate is a viable technique for wastewater treatment.

Photocatalytic degradation of H-acid over a novel TiO 2 thin film fixed bed reactor and in aqueous suspensions

The present work is focused on the heterogeneous photocatalytic degradation of H-acid, a toxic and non-biodegradable dye intermediate, in TiO 2 suspensions and TiO 2 thin film fixed bed reactor (TFFBR). The degradation studies in slurry form are investigated using TiO 2 Degussa P25 and different Millennium PC50, PC100 and PC500 photocatalysts under UV illumination. The study includes dark adsorption experiments in different pH conditions, influence of the amount of photocatalyst, effect of H-acid concentration, effect of pH on chemical oxygen demand (COD), biological oxygen demand (BOD) and the sulfate ion formation during the photocatalytic degradation. Photocatalytic treatment significantly reduces COD and increases the biodegradability of H-acid. The intermediates have been identified by LCMS. The study with slurry is extended to the immobilization of preformed TiO 2 Degussa P25 in thin film using an acrylic emulsion by simple spray technique on inert Cuddapah stone. This method of immobilization does not require the thermal treatment of the catalyst at high temperatures. It may be used for the photocatalytic treatment of effluents at a higher scale.

Decolorization and degradation of H-acid and other dyes using ferrous-hydrogen peroxide system.

In this study, advanced oxidation process utilizing Fenton's reaction was investigated for the decolorization and degradation of two commercial dyes viz., Red M5B, Blue MR and H-acid, a dye intermediate used in chemical industries for the synthesis of direct, reactive and azo dyes. Effect of Fe2 +, H2O2, pH, and contact time on the degradation of the dyes was studied. Maximum color and COD removal was obtained for Red MSB, H-acid and Blue MR at 10-25 mg/l of Fe2+ dose and 400-500 mg/l of H2O2 dose at pH 3.0. The initial oxidation reaction was found to fit into first order rate kinetics and the rate of oxidation of H-acid was higher than the other dyes. Release of chloride and sulfate from the Fenton's treated Red M5B dye and sulfate from H-acid and Blue MR indicates that the dye degradation proceeds through cleavage of the substituent group.

Monitoring of azo dye degradation processes in a bioreactor by on-line high-performance liquid chromatography

A technical solution and development of a method for on-line HPLC monitoring of bioreactor processes in a membrane reactor system are presented. Experiences in system design for the continuous coupling of a bioreactor system with capillary by-pass circuits using membrane flow cells and a dual HPLC system are reported. A continuously working integrated sample purification step by ultrafiltration with the membrane cell coupling is established. Using electrical switching valves and separated pumping and eluent systems, the dual HPLC system allows diode array detection as well as measurement of the refractive index. The application of the on-line HPLC monitoring system is demonstrated by measuring the anaerobic H-acid degradation kinetics. H-acid, 1-amino-8-hydroxynaphthalene-3,6-disulfonic acid, is one of the most important coupling components for a variety of direct, mordant, reactive dyes which remains in the process water and the textile dyeing effluents in high concentration.