Rate Of Decolourization Research Articles

Isolation of lignocellulolytic bacteria from oil palm mesocarp waste

In the present investigation, the bacterial strains were isolated from oil palm mesocarp waste dumped soil by serial dilution and pour plate method. The highest lignocellulolytic index was produced by bacterial isolate OPMW 6 (1.5 mm) followed by OPMW 5 (1.2 mm), OPMW 1 (0.83 mm), OPMW3 and OPMW 4 (0.71 mm). Changes in methylene blue color supplemented in nutrient broth from blue to light green or yellow were observed by three bacterial isolates (OPMW1, OPMW 3 and OPMW5), and rest of the bacterial isolatesrecorded less decolourization as the cultures were incubated between 24 and 48 hours respectively with highest percentage of dye decolourization produced by bacterial isolate i.e. OPMW5 (83.3%) and lowest rate ofdecolourization by bacterial isolate OPMW 6 (13.54%) as inoculated in nutrient broth supplemented with methylene blue dye. Utilization of gallic acid as supplemented in minimal salt media recorded positive reactionfor 4 bacterial isolates (OPMW 2, OPMW 5, OPMW 6 and OPMW 8) by the formation of dark colouration and addition ofa-naphthol in MSM inoculated broth culturesshowed formation of purple blue colour due to productionof laccase activity. Among the 4 best isolates having the highest indices, two isolates of bacteria (OPMW5 and OPMW6) had the best lignocellulolytic activity. Based on enzyme biosynthesis ability, the OPMW5 and OPMW6were selected as the best isolates as it can synthesie cellulase and ligninase enzymes. These enzymes are known to accelerate the degradation of oil palm mesocarp fibre substrate.

Solar light assisted degradation of Rhodamine B dye by chemically synthesized silver nanoparticles

Utilization of dyes and dyestuff is increasing day by day, which affects environmental health and sustainability. Rhodamine B (RhB) is a synthetic xanthene class of dye that has a major application in cosmetic, painting, printing, and textile industries. The toxicity of RhB has been reported in animals, insects as well as humans in parts per billion (ppb) concentration. Exposure to this dye causes skin irritation, nervous system issues, and developmental changes. Therefore, the remediation of the dye is a crucial factor. The aim of this study was solar-assisted photocatalytic degradation of RhB. Synthesis of silver nanoparticles (AgNPs) was carried out with chemical reduction method, and characterization with the X-ray diffraction (XRD). The photocatalytic activity was checked with 1000 mL wastewater in which 10 ppm dye was added. Optimization of physicochemical parameters was performed by one-factor-at-a-time (OFAT) method. Maximum 99.32 % decolourization was observed at 2 g/L catalyst concentration, pH = 6, and 10 ppm dye concentration in 50 min irradiation time at 0.19 mg/L/min rate of decolourization. The initial degradation was confirmed based on chemical oxygen demand (COD) reduction; 89.25 % COD removal at a 0.17 mg/L/min rate was observed. The confirmation of degradation was carried out with UV-visible spectrophotometer and high-performance thin-layer chromatography (HPTLC) analysis. AgNPs were the efficient catalyst for the degradation of RhB. The toxicity study proved that, after degradation of RhB with AgNPs, the degraded products were less toxic than the original ones.

Decolourization of Congo Red Dye using Solar/H2O2 Process

The Congo red dye was decolourized by advanced oxidation process using solar/H2O2 method and the effect of various parameters on decolourization like pH, H2O2 concentration, dye concentration, solar light intensity, additives, COD and TOC removal studies and kinetic studies were investigated. The photodegradation process was done by exposing dye solutions with the concentration of 100 mg/L treated with 50% H2O2 to sunlight with the lux intensity range of 60,000-90,000 lux. The best possible pH 2 with an optimal H2O2 concentration of 1000 mM to achieve 100% decolourization within the period of 5 h. The kinetic studies done on H2O2 concentration also proved that the high solar light intensity leads to higher decolourization and low solar light intensity leads to lesser decolourization. Addition of additives like H2PO4 – and Cl– leads to a decrease in the rate of decolourization. The removal of COD and TOC removal was found to be 83.26% and 5.18%, respectively.

Elucidation of fungal dye-decolourizing peroxidase (DyP) and ligninolytic enzyme activities in decolourization and mineralization of azo dyes.

The aim of the study is to investigate the efficiency of Geotrichum candidum in the decolourization and mineralization of synthetic azo dyes. It includes screening of enzymes from G. candidum and its optimization, followed by decolourization and mineralization studies. Decolourization was observed to be maximum in methyl orange (94·6%) followed by Congo red (85%), trypan blue (70·4%) and Eriochrome Black T (55·6%) in 48h, suggesting the plausible degradation of the azo dyes by G. candidum. The enzyme activity study showed that DyP-type peroxidase has highest activity of 900mUml-1 compared to that of laccase (405mUml-1 ) and lignin peroxidase (LiP) (324mUml-1 ) at optimized pH (6) and temperature (35°C). Moreover, the rate of decolourization was found to be directly proportional to the production of laccase and LiP, unlike DyP-type peroxidase. Furthermore, mineralization study demonstrated reduction in aromatic amines, showing 20% mineralization of methyl orange. Geotrichum candidum with its enzyme system is able to efficiently decolourize and mineralize the experimental azo dyes. The efficient decolourization and mineralization of azo dyes makes G. candidum a promising alternative in the treatment of textile effluent contaminated with azo dyes.

Degradation of Azo Dye (Acid Orange 7) in a Microbial Fuel Cell: Comparison Between Anodic Microbial-Mediated Reduction and Cathodic Laccase-Mediated Oxidation

More than 80 per cent of wastewater from industries is discharged into receiving water bodies without any pollution control. Microbial fuel cells (MFCs) are a promising technology for the simultaneous treatment of wastewater and electricity production. With regard to azo-dye containing wastewater (e.g. from textile manufacturing), the dye may be fed via the anode chamber containing electrochemically active bacteria or via the cathode chamber containing laccase enzyme as catalyst for oxygen reduction. This study investigated which of the two approaches is the best with regard to rate of decolourization of the dye (Acid orange 7), COD reduction and electricity production. The power density was higher for the MFCDye cathode (50±4 mW m-2, COD reduction 80.4±1.2%) compared with 42.5±2.6 mW m-2 (COD reduction 69±2%) for MFCDye anode. The time required for decolourization was longer in the MFCDye anode (Shewanella oneidensis) where only 20% decolourization was obtained after 24 h compared to 80% for the MFCDye cathode. The anodic dye degradation products were unstable when exposed to air resulting in regaining of colour. In case of degradation by laccase in the cathode chamber, the decolourization products were stable and simpler in chemical structure as determined by GC-MS. This work suggests that feeding azo dyes in cathode chambers of MFCs containing laccase is a better way of treating the dyes compared to the commonly used approach of feeding the dye in the anode chamber provided enzyme activity can be sustained.

Triphenylamine based reactive coloro/fluorimetric chemosensors: Structural isomerism and solvent dependent sensitivity and selectivity

Triphenyl amine based chemosensors, (2-(((2-(9H-carbazol-9-yl)phenyl)imino)methyl)-5-(diphenylamino)phenol (ortho-CPDP) and 2-(((4-(9H–carbazol-9-yl)phenyl)imino)methyl)-5-(diphenylamino)phenol (para-CPDP), showed solvent and isomerism dependent selective coloro/fluorometric sensing of multiple metal ions (Fe3+, Al3+ and Zn2+) with distinguishable responses. In CH3CN, ortho and para-CPDP selectively produced yellow color upon addition of Al3+ and Fe3+ that was slowly disappeared. The yellow color of ortho and para-CPDP in DMF was decolourised selectively by adding Al3+ and Fe3+. Both ortho and para-CPDP in CH3CN showed nearly similar rate of decolourization for Fe3+ and Al3+. However, the rate of decolourization of ortho and para-CPDP in DMF was different for Fe3+ (10μM, 8min) and Al3+ (5×10−4M, 40min) ions. The limit of detection of para-CPDP for Fe3+ is 10μM and Al3+ 500μM. The mechanistic studies revealed the imine hydrolysis of ortho and para-CPDP in presence of Lewis acidic Fe3+ and Al3+. The reactivity based sensing lead to high selectivity for Al3+ and Fe3+ ions. Further, para-CPDP exhibited selective fluorescence turn-on for Zn2+ in DMF (λmax=513nm) and detection limit of 6.0μM. Thus, reactive chemosensors, ortho and para-CPDP, exhibited selective and distinguishable colorimetric sensing of Fe3+ and Al3+ ions and isomerism and solvent dependent fluorescence sensing of Zn2+.

Mechanistic aspects of electro-catalytic reduction of Reactive Black 5 dye in a divided cell in the presence of silver nano-particles

Abstract Electro-catalytic Reduction (ECR) of Reactive Black 5 (RB5) as a model compound was studied in a divided cell using graphite cathode in the presence and absence of silver nano-particles (AgNPs). In the absence of AgNPs and at current density of 20 mA cm−2 percentage RB5 decolourization at the end of 180 min and first-order reaction rate constant were 80% and 0.021 min−1, respectively. The presence of 10 mM AgNPs significantly improved the extent and rate of decolourization (99% and 0.043 min−1, respectively) under identical reaction conditions. The enhanced decolourization in the presence of AgNPs was attributed to generation of a nucleophilic species on the surface of NPs. It seems that nascent hydrogen ( H ) generated on the surface of AgNPs interacts with Ag to form a nucleophile such as silver hydride (AgHx) that decolorizes RB5. UV–Visible spectroscopy and LC-MS analyses confirmed generation and accumulation of sodium 1,2,7-triamino-8-hydroxynaphthalene-3,6-disulfonate (TAHNDS) and sodium 2-(4-aminobenzene-sulphonyl)-ethoxi-sulphonate (ABSES) as products of decolourization. RB5 decolourization in the presence or absence of AgNPs proceeded through cleavage of azo bonds ( N N ). The rate and extent of RB5 decolourization increased with increase in AgNPs concentration up to 16 mM. AgNPs could be reused at least three times yielding comparable results to that of fresh AgNPs. The results obtained in this study may lead to development of process wherein AgNPs can be activated at one place and sent to remote places for reduction of an aqueous target compound without the need of a reducing agent.

Engineering anatase hierarchically cactus-like TiO2 arrays for photoelectrochemical and visualized sensing platform

This work described that one–step synthesis three dimensional anatase hierarchically cactus–like TiO2 arrays (AHCT) and their application in constructing a novel photoelectrochemical (PEC) and visualized sensing platform based on molecular imprinting technique, which reports its result with the prussian blue (PB) electrode served as the electrochromic indicator for the detection of glycoprotein (RNase B). The AHCT arrays were perpendicularly grown on FTO substrate with tunable sizes, offering many advantages, such as large contact area, rapid charge electron separation and transport. A possible formation process of the interesting AHCT arrays has been investigated based on time–dependent experiment. In addition, the PEC and visualized sensing platform was constructed based on the molecularly imprinted polymer modified AHCT arrays. Specifically, in the proposed system, the more RNase B being, the more insulating layer was formed on the surface of AHCT arrays that impeded the harvesting of light and electron transfer, resulting in the reduction of photocurrent. When upon light illumination, the photogenerated electrons flow through an external circuit to PB, leading to the reduction of PB to prussian white (PW), which is transparent. The rate of decolourization of PB is proportional to the concentration of RNase B. In this way, a visualized PEC sensing platform that gives its quantitative information could be performed by monitoring the change of color intensity. Under optimal conditions, the protocol possessed a detection range of 0.5pM to 2μM (r=0.997) and the limit of detection was 0.12 pM toward RNase B. Our method eliminates the need for sophisticated instruments and high detection expenses, making it possible to be a reliable alternative in resource–constrained regions.

A Comparison Study of New TiO2/PEG Immobilized Techniques Under Normal and Visible Light Irradiations

Novel photocatalysts of TiO 2 and TiO 2 /PEG were immobilized using new technique which is double sided adhesive tape (DSAT) as a thin layer binder onto glass plate. The photocatalytic activity study of immobilized/TiO 2 and immobilized/TiO 2 /PEG were carried out by irradiating of 36 mg L -1 MB dye in the presence of normal and visible light with rate of decolourization was estimated from aliquot concentration spectrophotometrically. The high photocatalytic activity from immobilized/TiO 2 /PEG was observed with the rate constants of ca 0.06 and 0.02 min -1 under normal and visible light irradiation respectively. An active photocatalytic activity was observed for immobilized/TiO 2 /PEG sample while no photocatalytic activity detected under immobilized/TiO 2 . The high photoactivity was also detected under normal light for immobilized/TiO 2 /PEG sample. This might be due to the presence of electron conjugate in PEG that acted as electron donor for TiO 2 thus increase the photocatalysis process. Moreover, this electron donor is reported to be able to become active under low energy visible light hence the immobilized/TiO 2 /PEG can perfomed its photoactivity under visible light irradiation.

Photo catalytic efficiency and kinetic studies of ZnO nanoparticles for the removal of basic dye Rhodamine B

The present study reports on the photo catalytic degradation of Rhodamine B, wet chemically synthesized ZnO photocatalyst. The average particle size and shape of synthesized ZnO were 24nm and spherical, subsequently. The experiment was carried out by irradiating the aqueous solutions of dye containing photocatalysts with UV. The rate of decolourization was estimated from residual concentration spectrophotometrically. The experiment was carried out by varying the amount of catalyst (0.5, 1, 1.5 and 2 g/L) and initial concentration of dye (10–40 mg/L). The experimental results indicated that the maximum decolourization (more than 90%) of dyes occurred with ZnO catalyst at 1.5 g/L catalyst dose. The percentage reduction of Rhodamine B was estimated under UV system. Dye adsorption equilibrium was described by the Langmuir and Freundlich adsorption isotherms over the entire concentration ranging from 10 to 40 mg/L. Adsorption data are used for modelling, from the first- and second-order kinetic equation. The characteristic results and dimensionless factors showed that ZnO nanoparticles can be employed as commercial adsorbents in the removal of Rhodamine B from aqueous solution and wastewater.

Decolourisation and Detoxification of Reactive Azo Dyes by Saccharothrix Aerocolonigenes TE5

Reactive azo dyes primarily present in the effluent of textile industries are recalcitrant molecules and are highly toxic enough to impart severe adverse effects on vital organs of human or animal system and are difficult to degrade by biological means. The present study is structured to study the decolourization and detoxification potential of Saccharothrix aerocolonigenes strain TE5 isolated from the soil contaminated with textile effluents. The percent of decolourization was calculated under static and shaking conditions by employing UV-VIS Spectroscopy. The effect of pH, temperature, carbon and nitrogen sources on the rate of decolourization was determined. The toxicity of the degraded products was assessed by germination assay.

UV/H2O2/TiO2/Zeolite Hybrid System for Treatment of Molasses Wastewater

Wastewater from molasses processing contains a large amount of coloured substances that give a recalcitrant dark brown colour and high organic load to the effluent. Photocatalytic decolourization of molasses wastewater was performed using titanium dioxide catalyst coated on the surface of South African natural zeolite using the solid-solid dispersion method. Addition of hydrogen peroxide as an oxidant was investigated and 30W UV-Clamp was used as source of irradiation. The Chemical Oxygen Demand (COD) of the wastewater treated was varied from 20 g/L to 1 g/L. Batch experiments were conducted in a thermostatic shaker fitted with the UV lamp. The effects of pH, catalyst loading, oxidant dosage and irradiation time on the COD reduction and decolourization of the Molasses Waste Water (MWW) were investigated in this study. The highest colour removal of more than 90% was achieved at pH = 4 and oxidant dosage of 1.47 mM, while low COD removal (< 20%) was observed during photodegradation. A H 2O2/UV/TiO 2 system achieved higher colour removal of 97% compared to a UV/TiO 2 system which achieved 44% while H 2O2 /UV system achieved 34% colour removal. The rate of decolourization was found to fitpseudo - first order reaction kinetics with the highest rate constant value of 1.36 x 10 -2 min -1 .

Decolourization of tartrazine from aqueous solutions by coupling electrocoagulation with ZnOphotocatalyst

Decolourization of tartrazine (C.I. Acid Yellow 23, AY23) in aqueous solutions has been investigated by coupling electrocoagulation and ZnO photocatalyst methods and also by a comparison between ZnO, UV, EC, UV/ZnO, UV/EC, and EC/UV/ZnO systems in the removal of AY23 as a model contaminant. Results indicated that the decolourization efficiency was in order of EC/UV/ZnO > UV/EC > EC > UV/ZnO > ZnO ≥ UV. Combining EC with UV/ZnO can trigger the Fenton or Fenton-like reaction, which accelerates the rate of decolourization. Desired operating conditions for decolourization of 40 mg·dm AY23 solution in EC/UV/ZnO process were [ZnO]0 = 650 mg·dm, [NaCl] = 800 mg·dm, light intensity = 31/2 W·m, current density = 120 A·m, electrodes distance = 15 mm, pH = 6.29, stirring rate = 900 rpm and electrodes of steel 304/Al, which yielded 99.70% colour removal in 5 min of treatment time.

Detoxification and mineralization of Acid Blue 74: study of an alternative secondary treatment to improve the enzymatic decolourization

Many reports describe the decolourization of dyes by fungal enzymes. However, these enzymes do not contribute to dye mineralization but only to its biotransformation into less coloured or colourless molecules persisting in solution. Therefore, it is essential to analyse the identity of the metabolites produced during enzymatic treatments and its biodegradation into an appropriate system. The present work examines the decolourization/detoxification of a simulated effluent (containing Acid Blue 74) by fungal enzymes and proposes a secondary treatment using an anaerobic system to improve the enzymatic decolourization through the complete mineralization of the dye. Ligninolytic enzymes were produced by solid culture using the thermo-tolerant fungus Fomes sp. EUM1. The enzymes produced showed a high rate of decolourization (>95 % in 5 h) and were stable at elevated temperature (40 °C) and ionic strength (NaCl, 50 mM). Isatin-5-sulphonic acid was identified via (1)H-NMR as oxidation product; tests using Daphnia magna revealed the non-toxic nature of this compound. To improve the enzymatic degradation and avoid coupling reactions between the oxidation products, the effluent was subjected to an anaerobic (methanogenic) treatment, which achieved high mineralization efficiencies (>85 %). To confirm the mineralization of isatin-5-sulphonic acid, a specific degradation study, which has not been reported before, with this single compound was conducted under the same conditions; the results showed high removal efficiencies (86 %) with methane production as evidence of mineralization. These results showed the applicability of an anaerobic methanogenic system to improve the enzymatic decolourization/detoxification of Acid Blue 74 and achieve its complete mineralization.

Decolourization of C.I. Reactive Orange 16 via photocatalysis involving TiO2/UV and TiO2/UV/oxidant systems

Abstract Decolourization of C.I. Reactive Orange 16 (RO16) via photocatalysis involving TiO2/UV and TiO2/UV/oxidant systems has been investigated. The experiments were carried out in a stirred cylindrical batch photoreactor under UV irradiation. The effects of pH, TiO2 concentration and addition of electron acceptors such as H2O2, Na2S2O8 and Cu+ ions were studied. The decolourization efficiency followed the order of pH 3 > pH 9 > pH 6 in TiO2/UV system. The addition of Cu+ ions to TiO2/UV/oxidant system significantly increased the decolourization efficiency. The performance of addition of 0.5 mM Cu+ ions to TiO2/UV/Na2S2O8 system was also evaluated by using synthetic dye-bath effluent. The results reveal that almost complete decolourization (99%) was achieved with RO16, while 76% decolourization was obtained with synthetic dyebath effluent after 360 min of reaction time. Similar trend was observed with COD measurements. The rate of decolourization of RO16 was found to follow pseudo-first order kinetics a...

Decolourization potential of white-rot fungus Phanerochaete chrysosporium on synthetic dye bath effluent containing Amido black 10B

Synthetic azo dyes are extensively used in textile industry and are not easily degraded into the environment due to their complex structure. Due to the low degree of fixation of these dyes to fabrics, more than 10–15% of the dye does not bind to fabrics during colour processing and release into water bodies as effluent cause serious environmental pollution. White-rot fungus is found to be capable of degrading lignin which has a complex structure similar to azo dyes. In this study, the decolourization potential of white-rot fungus Phanerochaete chrysosporium, which is capable of decolourizing synthetic dye bath effluent, was investigated. Maximum decolourization of 98% was achieved on the third day under normal conditions. The rate of decolourization carried out at different concentrations revealed that the increase in dye effluent concentration suppresses the percentage decolourization. The optimized amounts of nutrients were found to be 0.5%, 0.1% and 0.5% of glucose, manganese sulphate and ammonium salts, respectively. The addition of inducers such as starch and lignin increased enzyme production and the rate of decolourization.

Kinetic of Azo Dyes Decolourization by Enterobacteriaceae Species in the Intact Cell Assay System

The method Intact cell was adopted to assess the influencing factors on the process of decolourization ability of the enterobacteriaceaea specie isolates under predisposed environment. Taken into account several ingredient are added individually as well in combinations in the assay reaction. Values of dye decolourized in µg ml -1 with Multi vitanmins solution (MVS) with glucose 42.53; MVS 36.00; Riboflavin (RF) 39.00; Yeast extract 36.00 and B- complex 23.00 from the initial dye of 46.00µg ml -1 were observed , where as glucose, Ascorbic acid, Cysteine, Cetyl-trimethyl-ammonium bromide (CTAB), Sodium molybdate, Biotin, KNO3, NaNO2, folic acid and 1-amino-2- naphtho-4-sulfonic acid (ANSA) does not shows influence on to the process, but, some of them showed inhibitory effect toward the decolourization. It was observed that the riboflavin addition at 19.95 n moles ml -1 in the reaction mixture, rate of decolourization was suddenly change from 0.019 ∆A/minutes to 0.20 ∆A/minutes, which is extremely high by 10 fold fast and subsequently remains faster i.e 0.2 ∆A/minutes without further additional RF in the same assay mixture. Rate of decolourization with different concentrations of riboflavin i.e. 13.0 n moles ml -1 to 59.9 n moles ml -1 showed second order kinetic. This indicates that the minimum amount of RF is essential to trigger the process of decolourization by the intact cells under the assay condition. While five different azo dyes were subjected, showed diverse behavior on to the rate of decolourization. Results of entire study incite on role of riboflavin could to a certain extent act as a redox mediator in the reaction(s) process and electron mediator between intracellular pool to the dye available at periplasmic redox sink @ JASEM

Effect of ph and nutrient starvation on biodegradation of azo dyes by Cellulomonas sp.

The effect of pH and some nutrients starvation on biodegradation of azo dyes (Orange II and Direct Blue 71) by Cellulomonas sp. was investigated. Highest percentage decolourization values of 62.85% and 56.23% were obtained at pH 6.5 for Orange II and Direct Blue 71 respectively. Rate of decolourization decreased with increasing concentration of nitrate (sodium nitrate) and sulphate (magnesium sulphate heptahydrate). Highest percentage decolourization (83.75% for Orange II and 76.89% for Direct Blue 71) was obtained in positive controls (no nitrate added). Corresponding values for sulphate-limited conditions were 91.71% for Orange II and 76.25% for Direct Blue 71 in positive controls (no sulphate added). The nitrogen of the generated aromatic amines provided the sole source of nitrogen in positive controls. Desulphonation of the aromatic moiety provided the sole source of sulphur in the positive control medium. The study shows that detoxification of ecosystems contaminated with azo dyes are enhanced under nitrate and sulphate-limited conditions Keywords: Biodegradation, Cellulomonas sp., azo dyes, pH, nitrate, sulphate. AJAZEB Vol. 6 2004: pp. 51-55

Effect of inorganic oxidants in photodecolourization of an azo dye

Aqueous solutions of the dye Acid Orange 7 were decolourized in the presence of ultraviolet irradiation (UV) and photocatalyst, TiO 2. Decolourization rate was increased in the presence of UV/TiO 2 compared to UV alone. Addition of hydrogen peroxide, H 2O 2, in concentrations ranging from 8.82 × 10 −3 to 7.1 × 10 −2 M to the solution containing pollutant and TiO 2 (0.5 g l −1) resulted in increased rates of decolourization. The rate of dye decolourization using periodate, NaIO 4, (4.76 × 10 −5 to 1 × 10 −3 M) at TiO 2 concentration of 0.5 g l −1 under UV illumination was higher than that for UV/TiO 2/H 2O 2 and increases with periodate concentration. The rate of decolourization of Acid Orange 7 was found to follow first-order kinetics. Reaction rate orders with respect to the oxidant species were 0.51 and 0.8, respectively for H 2O 2 and NaIO 4. Kinetic parameters of the photodecolourization process such as apparent rate constant ( k app) and initial reaction rate ( R initial) and efficiency parameters such as apparent quantum yield ( Q app) and electrical energy per order (EE/O) were estimated and compared for UV/TiO 2, UV/TiO 2/H 2O 2 and UV/TiO 2/IO 4 − catalytic systems.

Decolourization of an Azo Dye by Heterogeneous Photocatalysis

The decolourization of the azo dye Acid Orange 7 was investigated using a heterogeneous photocatalysis which comprised irradiating aqueous solutions of the dye with UV light at a wavelength of 254 nm in the presence of either (TiO 2 + ZnO) mixture, [ ( Ti O 2 + ZnO ) / S 2 O 8 2 − + or [(TiO 2 + ZnO)/Ag 2SO 4] at a pH of 6.1. It was observed that the dye decolourization was enhanced using UV / [ ( Ti O 2 + ZnO ) / S 2 O 8 2 − ] and UV/[(TiO 2 + ZnO)/Ag 2SO 4] catalytic systems over UV/(TiO 2 + ZnO) alone. Also, it can be seen that increasing the concentration of oxidant (Na 2S 2O 8 or Ag 2SO 4) added to (TiO 2 + ZnO) mixture led to a higher rate of dye decolourization. Electrical energy per order (EE/O) was proposed to assess the relative performance of each catalytic system used. It was found that EE/O decreases with increasing the concentration of Na 2S 2O 8 and Ag 2SO 4.