Abstract
Aqueous pollution due to textile industry is an important issue. Photocatalysis is one of the methods used for eradication of dyes from textile industrial effluents. In this study, the synthesis, characterization and evaluation of photo catalytic activity of Ag-TiO2 is reported. TiO2 catalysts with 2, 4, 6 and 8% loading of Ag were prepared by green methods using Azadirachta indica leaves extract as reducing agent with titanium dioxide and silver nitrate as precursor materials. Prepared catalyst was characterized by advanced techniques and was used as catalyst for degradation of Methylene blue and Rhodamine B dyes. Deposition of Ag greatly enhanced the catalytic efficiency of TiO2 towards degradation of dyes. Irradiation of catalyst excites electrons from conduction band of catalyst to valence band yielding an electron-hole pair. This electron-hole pair undergoes secondary reactions and produce OH∙ radicals. These active radicals take part in degradation of dyes. More than 90% dyes were degraded in 120 min. Photo catalytic degradation of Methylene blue and Rhodamine B followed Eley-Rideal mechanism which states that dye react in fluid phase with adsorbed oxygen.
1 Introduction
Dyes and pigments are predominantly used in different industries and a reasonable amount of these compounds go to environment through industrial effluents. As these compounds are toxic and carcinogenic in nature, therefore, their impact on the environment is a major concern. Furthermore, these dyes impart color to aqueous body blocking the penetration of sunlight and dissolution of oxygen [1, 2, 3]. Thus, a number of physical and chemical techniques such as filtration, precipitation, coagulation, adsorption and oxidation have been pursued for elimination of these toxic compounds. Photocatalytic oxidation, which is one of the viable and developing methods utilized for destruction of toxic pollutants and dyes, has increased much research enthusiasm for late years. The photocatalytic oxidation technique has a number of preferences over traditional techniques, viz less energy requirement, no requirement for sludge disposal and complete degradation of pollutants [4, 5, 6, 7, 8, 9]. TiO2 has been broadly utilized as catalyst for photocatalytic oxidation of a wide scope of pollutants because of its low cost and high stability. However, the photocatalytic activity of TiO2 has been restrained due two reasons; firstly, the rate of electron–hole pair recombination formed by irradiation is relatively high and secondly, it has wide band gap (about 3.2 eV) [10, 11, 12, 13, 14]. These restrictions can be overcome by modification in electronic band structure of TiO2. This modification has been accomplished by addition of a substance like Ag that decreases the rate of recombination of electron–hole pair [15,16]. Although silver (Ag) is highly effective, however, it cannot be employed as photocatalyst because the recovery of Ag nanoparticles from reaction mixture is difficult. Immobilization of Ag nanoparticles on other substances like TiO2 is technique to produce an efficient photocatalyst for aqueous phase degradation of pollutants. Immobilization of Ag nanoparticles on TiO2 prevents the electron-hole pair recombination, thus enhancing the photocatalytic activity of TiO2 [17, 18, 19]. Different strategies have been utilized for fabrication of Ag-TiO2, however, green synthesis has received high consideration in which extract of plants is utilized as stabilizing and reducing agent. A number of plants have been used for green synthesis of nanoparticles [20, 21, 22, 23, 24, 25, 26, 27].
In present study, Ag-TiO2 is fabricated utilizing the aqueous extract of Azadirachta indica L, locally called as neem. The prepared Ag-TiO2 was employed as photocatalyst for degradation of Methylene blue and Rhodamine B dyes.
2 Experimental
2.1 Materials
TiO2 (Merck), AgNO3 (Alfa Aesar), Methylene blue (Merck), Rhodamine B (commercial grade), Azadirachta indica leaves (Botanical garden, University of Agriculture Faisalabad, Pakistan) and distilled water were used in this study.
2.2 Synthesis of Ag-TiO2
First, the dried leaves (20 g) of Azadirachta indica were boiled in distilled water for 2 h. Then, after cooling the mixture, the aqueous extract was separated by filtration and was used for synthesis of Ag-TiO2. For synthesis of Ag-TiO2, a 50 mL plant extract was added dropwise to a mixture containing a known amount of AgNO3 and TiO2 under continuous stirring. Afterward, the synthesized Ag-TiO2 was filtered, washed and dried at 80°C for 12 h. Ag-TiO2 catalysts with 2, 4, 6 and 8% Ag loading were prepared. The leaves of referred plant contain a variety of phytochemicals including flavonoids and phenolic components which are considered as reducing agent for reduction of Ag1+ to Ag [28, 29, 30, 31, 32].
2.3 Photocatalytic degradation experiment
The photocatalytic activity of Ag-TiO2 was demonstrated with two different solutions of Methylene blue (λmax= 660 nm) and Rhodamine B (λmax= 554 nm) in a batch reactor. A 50 mL dye solution was taken in a reactor vessel. Then, a pre-weighed amount of photocatalyst was suspended in dye solution for 30 min in dark. Finally, the reaction mixture was irradiated with UV light. Reaction samples were withdrawn from the reactor after regular time intervals and were analysed using UV– visible spectrophotometer (U-2800, HITACHI, Japan). Equation 1 was used to calculate the degradation efficiency.
where Ao is the initial and A is the final absorbance at λMax of each dye. Effect of Ag loading, temperature and concentration on degradation of dyes was also investigated.
2.4 Reaction kinetics
The kinetics of present degradation study can be described by pseudo first order kinetics model in terms of Eley– Rideal (E-R) mechanism. This mechanism is described by Eq. 2 which transforms to Eq. 3 and Eq. 4 by considering constant pressure of oxygen and integration respectively.
3 Results and discussion
3.1 Characterization
Phase investigation and crystallinity of synthesized Ag-TiO2 was performed by XRD measurement with JDX-3532 Japan X-Ray Diffractometer and the results are given in Figure 1. The XRD pattern of TiO2 is dominated with sharp and well-resolved peaks at 25°, 36°, 48° and 55° which correspond to (1-0-1), (0-0-4), (2-0-0) and (1-0-5) diffraction planes, respectively, of anatase structural phase (JCPDS# 21-1272). In spectrum of Ag-TiO2, additional peaks at 2θ 38° and 44° can be observed corresponding to face cantered cubic unit cell of Ag [33, 34, 35, 36, 37].
XRD pattern of TiO2 (A) and Ag-TiO2 (B).
Figure 2 shows the scanning electron micrographs of TiO2 and Ag-TiO2 recorded with JSM-5910 Japan Microscope. Micrographs show that particles of TiO2 are spherical, uniform and homogeneous in morphology. Furthermore, it can also be noted that the particles are well dispersed and non-agglomerated. The Ag particles deposited on TiO2 are also well dispersed. Uniformity and smoothness in shape and homogeneous nature of
Scanning electron micrographs: (a) TiO2, (b) Ag-TiO2.
catalyst particles play an important role in reproducible catalytic activities.
The particle size distribution of prepared catalysts measured with Analysette 22 Compact, Germany is given in Figure 3. The particle sizes ranges from 0.001 to 20 μm, however, 85% of the particles have particles size equal to or less than 2μm. The surface area measured with Quanta Chrome, Nova 2200e instrument was found as 58 m2g-1 and 51 m2g-1 for TiO2 and Ag-TiO2 respectively. The decrease in surface area by deposition of Ag on TiO2 might be due to blockage of micropores by Ag nanoparticles.
Particle size distribution of the catalysts particles: (A) TiO2, (B) Ag-TiO2.
3.2 Photocatalytic activity
Separate degradation experiments were performed with solutions of Methylene blue and Rhodamine B dye for evaluation of catalytic activity of biosynthesized Ag-TiO2. This investigation was performed by suspending a 0.1 g 6% Ag-TiO2 catalyst in 50 mL of 100 mg/ L dye solution at 40°C and the resulting data in terms of Ct/Co (Co and Ct represents initial concentration of dye and concentration of dye at different time interval respectively) is given in Figure 4. This data is derived from measurement of absorbance at different time interval at λmax of each dye. The data presented in Figure 4 indicates that fabrication of Ag enhanced the photocatalytic activity of TiO2 for degradation of dyes. Similarly, the effect of Ag loading on photocatalytic activity of TiO2 was also investigated. For this purpose, degradation of Methylene blue dye was studied with 2, 4, 6 and 8% loading of Ag under identical experimental
Photo degradation of Methylene blue dye catalyzed by TiO2 (A) and Ag-TiO2 (B) in aqueous medium.
conditions. It was found that 65, 84, 97 and 78% of dye degraded after 120 min of reaction with 2, 4, 6 and 8% Ag-TiO2 as catalyst respectively. Higher concentration of Ag block the active center of TiO2, therefore, the photocatalytic activity decreased at higher Ag loading. Hence, 6% loading of Ag was considered as optimum loading [38,39]. It is proposed that heterogeneous photocatalytic degradation reaction takes place through the creation of positive hole
Photo degradation of Rhodamine B dye catalyzed by TiO2 (A) and Ag-TiO2 (B) in aqueous medium.
series of further reaction. The proposed mechanism was confirmed by performing the degradation experiments with Methylene blue dye in absence of irradiation. The results showed that degradation efficiency [30] in absence of light was much lower in comparison to degradation efficiency under irradiation (97%). In another experiment, the degradation efficiency was observed as 48% in the presence of isopropyl alcohol, OH∙ radical scavenger [40]. These results support the proposed mechanism. The proposed mechanism can be summarized as follows:
The deposition of Ag reinforces the catalytic activities of TiO2 because the Ag nanoparticles prevent the recombination of positive holes and photo excited electrons [36,37,41,42].
3.3 Effect of temperature
Generally, temperature affects the rate of reactions, therefore, we explored the temperature dependence of present catalytic system. For this purpose, separate catalytic experiments were performed with 50 mL of 100 mg/L dye solution over 0.1 g of 6% Ag-TiO2 at 30, 40 and 50°C. The results are given in Figure 5. It can be noted that temperature does not affect significantly the rate of reaction in present study. It is due the fact that photochemical reactions are generally less temperature dependent [4,5]. The experimental data at different temperatures was analysed according to pseudo first order kinetics equation (Eq. 4) and results are given in Figure 6. The slop of straight lines gives the rate constants which are given in Table 1. The activation energy determined
Ag-TiO2 catalyzed photo degradation of (a) Methylene blue dye and (b) Rhodamine B dye, both at various temperatures.
Kinetics of Ag-TiO2 catalyzed photo degradation of (a) Methylene blue dye and (b) Rhodamine B dye, both at various temperatures.
Rate constants of Ag-TiO2 catalyzed photo degradation of Methylene blue and Rhodamine B dye at various temperatures.
| T (°C) | Methylene blue | Rhodamine B | ||
|---|---|---|---|---|
| k (per min) | R2 | k (per min) | R2 | |
| 30 | 0.0141 | 0.984 | 0.0095 | 0.0981 |
| 40 | 0.0189 | 0.979 | 0.0139 | 0.976 |
| 50 | 0.0221 | 0.991 | 0.0157 | 0.991 |
by application of Arrhenius equation to rate constants at various temperature was found to be 27.1 and 20.4 kJ/mol for photo degradation of Methylene blue and Rhodamine B dye respectively.
3.4 Effect of initial concentration of dye
To investigate the effect of initial concentration of dye on rate of reaction, separate experiments were performed with 100, 200 and 300 mg/L as initial concentration of dyes. Photocatalytic degradation experiments for Methylene blue and Rhodamine B dye were performed at 40°C with 6% Ag-TiO2 catalyst. It was found that 97, 79 and 60% of Methylene blue dye degraded with 100, 200 and 300 mg/ L as initial concentration after 120 min of reaction respectively. Similarly, 90, 74 and 58% Rhodamine B dye degraded after 120 min of reaction with 100, 200 and 300 mg/ L as initial concentration respectively. The experimental data with various initial concentration of dyes was analysed according to first order kinetic equation (Eq. 4) and the results are given in Figure 7. The rate constants determined from the slops of straight lines in Figure 7 are given in Table 2. The data listed in Table 2 shows that rate constants decreases with increase in initial concentration of dye.
Kinetics of Ag-TiO2 catalyzed photo degradation of (a) Methylene blue dye and (b) Rhodamine B dye, both with various initial concentrations.
It can be noted that increase in concentration causes a decrease in degradation efficiency, which is due to two reasons. Frist, the concentrated solution becomes more intense in colour which results in hindrance to penetration of radiations to the catalyst surface. Secondly, as other experimental conditions are same, so the ratio of number of OH∙ radicals to number of molecules of dye decreases with increase in concentration, hence, the rate of reaction decreases with increase in initial concentration of dye [4,5,36,37,43,44].
3.5 Effect of pH
pH of reaction mixture is also an experimental parameter that affects the photo degradation efficiency of dyes. The
Rate constants of Ag-TiO2 catalyzed photo degradation of Methylene blue and Rhodamine B dye with various initial concentrations of dyes.
| Conc. (mg/L) | Methylene blue | Rhodamine B | ||
|---|---|---|---|---|
| k (per min) | R2 | k (per min) | R2 | |
| 100 | 0.0189 | 0.979 | 0.0139 | 0.976 |
| 200 | 0.0125 | 0.979 | 0.0091 | 0.969 |
| 300 | 0.0095 | 0.981 | 0.0068 | 0.959 |
surface charge of titania changes with variation of solution pH and changes the catalytic activity of TiO2 particles. The surface of TiO2 becomes positive and negative in acidic and alkaline condition respectively. As both Methylene blue and Rhodamine B dyes are cationic dyes therefore, the alkaline condition favors the adsorption of these dyes on TiO2 surface. Furthermore, the OH∙ radicals are easier to be generated in alkaline solution due to oxidation of OH ions, thus, the degradation efficiency increases with pH [2, 45, 46, 47, 48, 49, 50]. Therefore, both Methylene blue and Rhodamine B dyes have shown to degrade more at pH 10. Other researchers have also reported similar trends [36,37,51,52].
4 Conclusions
Ag-TiO2 was successfully fabricated by environmentally friendly and low cost green method using Azadirachta indica leaves extract as reducing agent and titanium dioxide and silver nitrate as precursor materials. The photo catalytic activities of prepared particles were evaluated by degrading Methylene blue and Rhodamine B dyes under UV irradiation. The 6% Ag-TiO2 exhibited the best catalytic activity for degradation of Methylene blue and Rhodamine B dyes. More than 90% dyes were degraded in 120 min. It was found that there was no loss in catalytic efficiency of prepared Ag-TiO2 catalyst after recycling it for two times. Photocatalytic degradation of Methylene blue and Rhodamine B followed Eley-Rideal mechanism which states that dye react in fluid phase with adsorbed oxygen.
Acknowledgment
Project No. 65-CHM-5 of GCUF-RSP is appreciated.
References
[1] Muthirulan P., Devi C.N., Sundaram M.M., Synchronous role of coupled adsorption and photocatalytic degradation on CAC–TiO2 composite generating excellent mineralization of alizarin cyanine green dye in aqueous solution. Arab. J. Chem., 2017, 10, S1477-S1483.10.1016/j.arabjc.2013.04.028Search in Google Scholar
[2] Rauf M.A., Meetani M.A., Hisaindee S., An overview on the photocatalytic degradation of azo dyes in the presence of TiO2 doped with selective transition metals. Desalination, 2011, 276, 13-27.10.1016/j.desal.2011.03.071Search in Google Scholar
[3] Sood S., Kumar S., Umar A., Kaur A., Mehta S.K., Kansal S.K., TiO2 quantum dots for the photocatalytic degradation of indigo carmine dye. J. Alloy. Compd., 2015, 650, 193-198.10.1016/j.jallcom.2015.07.164Search in Google Scholar
[4] Gupta V.K., Jain R., Agarwal S., Nayak A., Shrivastava M., Photodegradation of hazardous dye quinoline yellow catalyzed by TiO2 J. Colloid Interf. Sci., 2012, 366, 135-140.10.1016/j.jcis.2011.08.059Search in Google Scholar
[5] Gupta V.K., Jain R.J., Mittal A., Saleh T.A., Nayak A., Agarwal S., et al., Photo-catalytic degradation of toxic dye amaranth on TiO2/UV in aqueous suspensions. Mater. Sci. Eng., 2012, 332, 12-17.10.1016/j.msec.2011.08.018Search in Google Scholar
[6] Ata S., Shaheen I., Ayne Q., Ghafoor S., Sultan M., Majid F., et al., Graphene and silver decorated ZnO composite synthesis, characterization and photocatalytic activity evaluation. Diam. Relat. Mater., 2018, 90, 26-31.10.1016/j.diamond.2018.09.015Search in Google Scholar
[7] Arshad M., Qayyum A., Abbas G., Haider R., Iqbal M., Nazir A., Influence of different solvents on portrayal and photocatalytic activity of tin-doped zinc oxide nanoparticles. J. Mol. Liq., 2018, 260, 272-278.10.1016/j.molliq.2018.03.074Search in Google Scholar
[8] Arshad M., Qayyum A., Abbas G., Soomro G.A., Nazir A., Munir B., et al., Zn-doped SiO2 nanoparticles preparation and characterization under the effect of various solvents: Antibacterial, antifungal and photocatlytic performance evaluation. J. Photoch. Photobio. B, 2018, 185, 176-183.10.1016/j.jphotobiol.2018.04.043Search in Google Scholar
[9] Arshad M., Abbas M., Haque S.E., Farrukh M.A., Ali A., Rizvi H., et al., Synthesis and characterization of SiO2 doped Fe2O3 nanoparticles: Photocatalytic and antimicrobial activity evaluation. J. Mol. Struct., 2019, 1180, 244-250.10.1016/j.molstruc.2018.11.104Search in Google Scholar
[10] Silva C.G., Faria J.L., Photochemical and photocatalytic degradation of an azo dye in aqueous solution by UV irradiation. J. Photoch. Photobio. A, 2003, 155, 133-143.10.1016/S1010-6030(02)00374-XSearch in Google Scholar
[11] Wu Y., Zhou Y., Liu Y., Wang Y., Yang L., Li C., Photocatalytic performances and characterizations of sea urchin-like N, Ce codoped TiO2 photocatalyst. Mater. Res. Innov., 2017, 21, 33-39.10.1080/14328917.2016.1168088Search in Google Scholar
[12] Nada A.A., Tantawy H.R., Elsayed M.A., Bechelany M., Elmowafy M.E., Elaboration of nano titania-magnetic reduced graphene oxide for degradation of tartrazine dye in aqueous solution. Solid State Sci., 2018, 78, 116-125.10.1016/j.solidstatesciences.2018.02.014Search in Google Scholar
[13] Ghasemi S., Hashemian S., Alamolhoda A., Gocheva I., Setayesh S.R., Plasmon enhanced photocatalytic activity of Au@ TiO2-graphene nanocomposite under visible light for degradation of pollutants. Mater. Res. Bull., 2017, 87, 40-47.10.1016/j.materresbull.2016.11.020Search in Google Scholar
[14] El-Maghrabi H.H., Barhoum A., Nada A.A., Moustafa Y.M., Seliman S.M., Youssef A.M., et al., Synthesis of mesoporous core-shell CdS@TiO2 (0D and 1D) photocatalysts for solar-driven hydrogen fuel production. J. Photochem. Photobiol. Chem., 2018, 351, 261-270.10.1016/j.jphotochem.2017.10.048Search in Google Scholar
[15] Nasr M., Balme S., Eid C., Habchi R., Miele P., Bechelany M., Enhanced visible-light photocatalytic performance of electrospun rGO/TiO2 composite nanofibers. J. Phys. Chem. C, 2016, 121, 261-269.10.1021/acs.jpcc.6b08840Search in Google Scholar
[16] Bhanvase B., Shende T., Sonawane S., A review on graphene– TiO2 and doped graphene–TiO2 nanocomposite photocatalyst for water and wastewater treatment. Environ. Technol. Rev., 2017, 6, 1-14.10.1080/21622515.2016.1264489Search in Google Scholar
[17] Ziyu L., Zhigang J., Wenwen L., Jianhong L., Shan J., Shengbiao L., et al., Synthesis of Ag/AgCl nanoparticles immobilized on CoFe2O4 fibers and their photocatalytic degradation for methyl orange. Rare Metal Mater. Eng., 2017, 46, 3669-3674.10.1016/S1875-5372(18)30055-9Search in Google Scholar
[18] Li W., Ma Z., Bai G., Hu J., Guo X., Dai B., et al., Dopamine-assisted one-step fabrication of Ag@AgCl nanophotocatalyst with tunable morphology, composition and improved photocatalytic performance. Appl. Catal. B-Environ., 2015, 174, 43-48.10.1016/j.apcatb.2015.02.029Search in Google Scholar
[19] Lu L., Li J., Yu J., Song P., Ng D.H., A hierarchically porous MgFe2O4/γ-Fe2O3 magnetic microspheres for efficient removals of dye and pharmaceutical from water. Chem. Eng. J., 2016, 283, 524-534.10.1016/j.cej.2015.07.081Search in Google Scholar
[20] Kamran U., Bhatti H.N., Iqbal M., Jamil S., Zahid M., Biogenic synthesis, characterization and investigation of photocatalytic and antimicrobial activity of manganese nanoparticles synthesized from Cinnamomum verum bark extract. J. Mol. Struc., 2019, 1179, 532-539.10.1016/j.molstruc.2018.11.006Search in Google Scholar
[21] Bibi I., Kamal S., Ahmad A., Iqbal M., Nouren S., Jilani K., et al., Nickel nanoparticle synthesis using Camellia Sinensis as reducing and capping agent: Growth mechanism and photo-catalytic activity evaluation. Int. J. Bio. Macromol., 2017, 103, 783-790.10.1016/j.ijbiomac.2017.05.023Search in Google Scholar PubMed
[22] Bibi I., Nazar N., Iqbal M., Kamal S., Nawaz H., Nouren S., et al., Green and eco-friendly synthesis of cobalt-oxide nanoparticle: Characterization and photo-catalytic activity. Adv. Powder Technol., 2017, 28, 2035-2043.10.1016/j.apt.2017.05.008Search in Google Scholar
[23] Nazar N., Bibi I., Kamal S., Iqbal M., Nouren S., Jilani K., et al., Cu nanoparticles synthesis using biological molecule of P. granatum seeds extract as reducing and capping agent: Growth mechanism and photo-catalytic activity. Int. J. Bio. Macromol., 2018, 106, 1203-1210.10.1016/j.ijbiomac.2017.08.126Search in Google Scholar PubMed
[24] Alzohairy M.A., Therapeutics role of Azadirachta indica (Neem) and their active constituents in diseases prevention and treatment. Evid. Based Compl. Alter. Med., 2016, 7382506.10.1155/2016/7382506Search in Google Scholar PubMed PubMed Central
[25] Fan X., Lin P., Lu X., Zi J., A new spiro-type limonoid from Azadirachta indica A. Juss. Tetrahedron Lett., 2019, 60, 1158-1160.10.1016/j.tetlet.2019.03.050Search in Google Scholar
[26] Rajendaran K., Muthuramalingam R., Ayyadurai S., Green synthesis of Ag-Mo/CuO nanoparticles using Azadirachta indica leaf extracts to study its solar photocatalytic and antimicrobial activities. Mat. Sci. Semicon. Proc., 2019, 91, 230-238.10.1016/j.mssp.2018.11.021Search in Google Scholar
[27] Babatunde D.E., Otusemade G.O., Efeovbokhan V.E., Ojewumi M.E., Bolade O.P., Owoeye T.F., Chemical composition of steam and solvent crude oil extracts from Azadirachta indica leaves. Chem. Data Collec., 2019, 20, 100208.10.1016/j.cdc.2019.100208Search in Google Scholar
[28] Hossain M.A., Al-Toubi W.A.S., Al-Riyami Q.A., Al-Sabahi J.N., Identification and characterization of chemical compounds in different crude extracts from leaves of Omani neem J. Taibah Uni. Sci., 2013, 7, 181-188.10.1016/j.jtusci.2013.05.003Search in Google Scholar
[29] Dash S.P., Dixit S., Sahoo S., Phytochemical and biochemical characterizations from leaf extracts from Azadirachta indica An important medicinal plant. Anal. Biochem., 2017, 6, 1000323.Search in Google Scholar
[30] Ayodhya D., Veerabhadram G., One-pot green synthesis, characterization, photocatalytic, sensing and antimicrobial studies of Calotropis gigantea leaf extract capped CdS NPs. Mater. Sci. Eng. B, 2017, 225, 33-44.10.1016/j.mseb.2017.08.008Search in Google Scholar
[31] Ahluwalia V., Elumalai S., Kumar V., Kumar S., Sangwan R.S., Nano silver particle synthesis using Swertia paniculata herbal extract and its antimicrobial activity. Microb. Pathogenesis, 2018, 114, 402-408.10.1016/j.micpath.2017.11.052Search in Google Scholar PubMed
[32] Bordbar M., Negahdar N., Nasrollahzadeh M., Melissa officinalis L. leaf extract assisted green synthesis of CuO/ZnO nanocomposite for the reduction of 4-nitrophenol and Rhodamine B. Sep. Purif. Technol., 2018, 191, 295-300.10.1016/j.seppur.2017.09.044Search in Google Scholar
[33] Deshmane V.G., Owen S.L., Abrokwah R.Y., Kuila D., Mesoporous nanocrystalline TiO2 supported metal (Cu, Co, Ni, Pd, Zn, and Sn) catalysts: Effect of metal-support interactions on steam reforming of methanol. J. Mol. Catal. A-Chem., 2015, 408, 202-213.10.1016/j.molcata.2015.07.023Search in Google Scholar
[34] Atarod M., Nasrollahzadeh M., Sajadi S.M., Euphorbia heterophylla leaf extract mediated green synthesis of Ag/TiO2 nanocomposite and investigation of its excellent catalytic activity for reduction of variety of dyes in water. J. Colloid Interf. Sci., 2016, 462, 272-279.10.1016/j.jcis.2015.09.073Search in Google Scholar PubMed
[35] Xu M., Wang Y., Geng J., Jing D., Photodecomposition of NOx on Ag/TiO2 composite catalysts in a gas phase reactor. Chem. Eng. J., 2017, 307, 181-188.10.1016/j.cej.2016.08.080Search in Google Scholar
[36] Saeed M., Ahmad A., Boddula R., Din I., Haq A., Azhar A., Ag@MnxOy An effective catalyst for photo-degradation of rhodamine B dye. Environ. Chem. Lett., 2018, 16, 287-294.10.1007/s10311-017-0661-zSearch in Google Scholar
[37] Saeed M., Muneer M., Mumtaz N., Siddique M., Akran N., Humayun M., Ag-Co3O4 Synthesis, characterization and evaluation of its photo-catalytic activity towards degradation of rhodamine B dye in aqueous medium. Chin. J. Chem. Eng., 2018, 26, 1264-1269.10.1016/j.cjche.2018.02.024Search in Google Scholar
[38] Chen G., Si X., Yu J., Bai H., Zhang X., Doping nano-Co3O4 surface with bigger nanosized Ag and its photocatalytic properties for visible light photo degradation of organic dyes. Appl. Surf. Sci., 2015, 330, 191-199.10.1016/j.apsusc.2015.01.011Search in Google Scholar
[39] Jermwongratanachai T., Jacobs G., Ma W.P., Shafer W.D., Gnanamani M.K., Gao P., et al., Fischer–Tropsch synthesis: comparisons between Pt and Ag promoted Co/Al2O3 catalysts for reducibility, local atomic structure, catalytic activity, and oxidation–reduction (OR) cycles. Appl. Catal. A-Gen., 2013, 464, 165-180.10.1016/j.apcata.2013.05.040Search in Google Scholar
[40] Yue B., Zhou Y., Xu J., Wu Z., Zhang X., Zou Y., et al., Photocatalytic degradation of aqueous 4-chlorophenol by silica-immobilized polyoxometalates. Environ. Sci. Technol., 2002, 36, 1325-1329.10.1021/es011038uSearch in Google Scholar PubMed
[41] Vidyasagar D., Ghugal S.G., Kulkarni A., Mishra P., Shende A.G., Umare J.S.S., et al., Silver/Silver(II) oxide (Ag/AgO) loaded graphitic carbon nitride microspheres: An effective visible light active photocatalyst for degradation of acidic dyes and bacterial inactivation. Appl. Catal. B-Environ., 2018, 221, 339-348.10.1016/j.apcatb.2017.09.030Search in Google Scholar
[42] Vartooni A.R., Nasrollahzadeh M., Niasari M.S., Atarod M., Photocatalytic degradation of azo dyes by titanium dioxide supported silver nanoparticles prepared by a green method using Carpobrotus acinaciformis extract. J. Alloy. Compd., 2016, 689, 15-20.10.1016/j.jallcom.2016.07.253Search in Google Scholar
[43] Davis R.J., Gainer J.L., Neal G., Wenwu I., Photocatalytic decolourisation of wastewater dyes. Water Environ. Res., 1994, 66, 50-53.10.2175/WER.66.1.8Search in Google Scholar
[44] Pare B., Jonnalagadda S.B., Tomar H., Singh P., Bhagwat V.W., ZnO assisted photocatalytic degradation of acridine orange in aqueous solution using visible irradiation. Desalination, 2008, 232, 80-90.10.1016/j.desal.2008.01.007Search in Google Scholar
[45] Konstantinou I.K., Albanis T.A., TiO2-assisted photocatalytic degradation of azo dyes in aqueous solution: kinetic and mechanistic investigations: a review. Appl. Catal. B-Environ., 2004, 49, 1-14.10.1016/j.apcatb.2003.11.010Search in Google Scholar
[46] Lachheb H., Puzenat E., Houas A., Ksibi M., Elaloui E., Guillard C., et al., Photocatalytic degradation of various types of dyes (Alizarin S, Crocein Orange G, Methyl Red, Congo Red, Methylene Blue) in water by UV-irradiated titania. Appl. Catal. B-Environ., 2002, 39, 75-90.10.1016/S0926-3373(02)00078-4Search in Google Scholar
[47] Baran W., Makowski A., Wardas W., The effect of UV radiation absorption of cationic and anionic dye solutions on their photocatalytic degradation in the presence TiO2 Dyes Pigments, 2008, 76, 226-230.10.1016/j.dyepig.2006.08.031Search in Google Scholar
[48] Augugliaro V, Baiocchi C, Prevot A.B., López E.G., Loddo V., Malato S., et al., Azo-dyes photocatalytic degradation in aqueous suspension of TiO2 under solar irradiation. Chemosphere, 2002, 49, 1223-1230.10.1016/S0045-6535(02)00489-7Search in Google Scholar
[49] Soutsas K., Karayannis V., Poulios I., Riga A., Ntampegliotis K., Spiliotis X., et al., Decolorization and degradation of reactive azo dyes via heterogeneous photocatalytic processes. Desalination, 2010, 250, 345-350.10.1016/j.desal.2009.09.054Search in Google Scholar
[50] Behnajady M.A, Modirshahla N., Shokri M., Photodestruction of Acid Orange 7 (AO7) in aqueous solutions by UV/H2O2 influence of operational parameters. Chemosphere, 2004, 55, 129-134.10.1016/j.chemosphere.2003.10.054Search in Google Scholar
[51] Zielinska B., Grzechulska J., Grzmil B., Morawski A.W., Photocatalytic degradation of Reactive Black 5: a comparison between TiO2-Tytanpol A11 and TiO2-Degussa P25 photocatalysts. Appl. Catal. B-Environ., 2001, 35, L1-L7.10.1016/S0926-3373(01)00230-2Search in Google Scholar
[52] Guillard C., Lachheb H, Houas A., Ksibi M., Elaloui E., Herrmann J.M., Influence of chemical structure of dyes, of pH and of inorganic salts on their photocatalytic degradation by TiO2 comparison of the efficiency of powder and supported TiO2 J. Photoch. Photobio. A, 2003, 158, 27-36.10.1016/S1010-6030(03)00016-9Search in Google Scholar
© 2019 Saeed et al., published by De Gruyter
This work is licensed under the Creative Commons Attribution 4.0 Public License.
