Comparing the efficiency of UV/ZrO2 and UV/H2O2/ZrO2 photocatalytic processes in furfural removal from aqueous solution
- 463 Downloads
Furfural is a toxic chemical compound that is widely applied as a solvent in a great many of industries, and it can cause many problems to the human beings and environment. Various methods of removing furfural from the wastewaters have been studied. AOPs methods are utilized for the elimination of a vast majority of the pollutants due to their high efficiency as well as for their lack of creating secondary contamination. Therefore, the present study aims at comparing the efficiency of UV/ZrO2 and UV/H2O2/ZrO2 photocatalytic processes in removing furfural from aqueous solutions. The solution’s initial pH, furfural’s concentration, zirconium catalyst dosage and time were investigated as the parameters influencing the removal efficiency by the two foresaid processes, and the effect of H2O2 addition in various concentrations into UV/H2O2/ZrO2 process was also evaluated. Spectrophotometer device was employed to assay the concentration of the residual furfural. The results indicated that the pH of the environment, the amount of the nanoparticle and H2O2 input concentration largely influence the furfural omission. The optimal condition for the removal of furfural in UV/ZrO2 process in an initial concentration of 20 mg/L, a pH equal to 3, a catalyst dose of 0.25 g/L during a period of 60-min time was 81.6%, and it was 99% for UV/H2O2/ZrO2 process in a pH equal to 7 with the addition of H2O2 for a concentration of 0.75 mL/L under the same conditions. Generally, it can be concluded that UV/H2O2/ZrO2 and UV/ZrO2 photocatalytic processes can effectively be applied to remove furfural from the aqueous solutions, especially in lower concentrations.
KeywordsFurfural Photocatalytic processes Zirconium dioxide Hydrogen peroxidation
Furfural has numerous use cases and is extensively and widely utilized. Furfural and its derivatives are used in the production processes of solid resins as well as plastic and paper (Fazlzadeh et al. 2018). Also, this chemical compound is most frequently used in petroleum and oil purification industry (Hoydonckx et al. 2000; Presto et al. 2007; Borghei and Hosseini 2008). In such a manner that the furfural concentrations of the wastewaters stemming from rubber and plastic manufacturing, furfural production and oil refineries are reportedly 500 mg/L, 600 mg/L and 1000 mg/L, respectively (Wirtz and Dague 1993; Presto et al. 2007; Sahu et al. 2007). Since furfural is a toxic chemical compound and persistent in the environment (Faramarzpour et al. 2009; Leili et al. 2013), the wastewaters containing furfural should be appropriately treated before being discharged to the environment so as to preserve the human health and conserve the environment.
There are numerous methods studied for the removal of furfural from the wastewaters including the surface absorption and oxidation methods (Sahu et al. 2007, 2008; Borghei and Hosseini 2008; Singh et al. 2009). Advanced oxidation processes (AOPs) such as UV/H2O2, TiO2/UV, UV/O3, O3/H2O2, US/H2O2/Fe2+ and others of the like are inter alia these methods. These processes featuring very high efficiency and lacking secondary pollutions can be used for the degradation of a great many of the pollutants (Rahmani et al. 2017; Seid-Mohammadi et al. 2017).
Photocatalysis is an AOP process, that is, a light absorption-based process by a solid substrate (Samarghandi et al. 2011; Parastar et al. 2013). In this process, the nanoparticles act as catalysts to absorb the UV high-energy photons subsequent to which active chemical materials like hydroxyl radicals are formed (Parga et al. 2003; Fazlzadeh et al. 2016a, 2017a, b; Azizl et al. 2017; Khosravi et al. 2018). Photocatalytic oxidation processes by the use of metal oxides have been taken into consideration in the process of removing organic pollutants and microbial factors during the recent years, and the photocatalytic characteristics of metal oxides such as ZrO, ZnO and TiO2 have been explored (Kamat et al. 2008; Fazlzadeh et al. 2016b, 2017a). Recently, a compound, called ZrO2, has been considered as a photocatalyst in inhomogeneous photochemical reactions. This compound has been applied in the production of hydrogen from water as well as for the oxidation of 2-propanol to acetone, and propane and ethane oxidation, photolysis of 4-chlorophenol, 4-nitrophenol and 1, 4-pentandiole due to its high band gap energy and the high negative conduction band potential (Botta et al. 1999).
The study by Karunakaran et al. (2012) on phenol decomposition by the use of reinforced ZrO2 with various semiconductors in the presence of UV rays indicated that the photocatalytic decomposition linearly increases with the phenol concentration and the light intensity and decreases with the increase in pH. Also, semiconductors’ precipitation enhanced the efficiency of ZrO2 (Karunakaran et al. 2012). In the study that was conducted by Malakootian et al. (2013) on the efficiency of UV/ZrO2 and UV/H2O2/ZrO2 in removing cyanide from aqueous solutions, it was concluded that the efficiency of UV/ZrO2 process is increased with the increase in the amount of nanoparticle used and the extension of irradiation time and reduction in pH and that the increase in the cyanide concentration depreciates the efficiency of both of the processes. Increasing the H2O2 to an optimal amount (0.5 mL/100 mL) enhances the efficiency of UV/H2O2/ZrO2 process, but the use of higher H2O2 amounts decreases the process output (Malakootian et al. 2013).
The objective of the present study is to investigate the efficiency of photocatalytic process of furfural removal by the use of UV/ZrO2 and UV/H2O2/ZrO2 from the aqueous solutions and then to compare the two processes. Moreover, the study evaluates the direct photolysis states (UV alone), UV/H2O2 and ZrO2/H2O2 in furfural removal. The COD of the solution was also measured under optimal conditions so as to assess the COD variations caused by the changes in furfural concentration.
The experiments were conducted by the use of zirconia nanoparticles and hydrogen peroxidation in various ranges of pH so as to determine the optimal pH value. The pH ranged from 3 to 11 for both of the processes. pH regulation was conducted by the use of normal 0.1 NaOH and H2SO4. To perform the experiment, first of all, the initial furfural solution, with a 10 g/L concentration, was made in deionized distilled water. According to the studies undertaken in this regard, the furfural concentration in the current research paper was selected equal to its real concentrations in wastewaters. Zirconia nanoparticle concentration in UV/ZrO2 process was in a range from 0.1 to 1 g/L with an optimal pH of the first stage (Malakootian and Hashemi Cholicheh 2012; Malakootian et al. 2013). After acquiring the optimal concentration of each of the oxidant materials (zirconia and hydrogen peroxide), furfural removal was continued by blending H2O2 and ZrO2 in UV/H2O2/ZrO2 process so as to attain a high furfural elimination output. Hydrogen peroxidation concentration in UV/H2O2/ZrO2 process in an optimal pH value in a range from 0.1 to 1.5 mL/L was increased and an optimal concentration was obtained. Next, the effect of furfural concentration was investigated in a 20–1000 mg/L range on its removal (Wirtz and Dague 1993; Sahu et al. 2007; Borghei and Hosseini 2008). COD of the initial and secondary solutions was measured under optimum conditions (only for a 500 mg/L concentration of furfural) so that the COD variations caused by the furfural concentration changes can be assessed. To determine the effect of reaction time on UV/ZrO2 and UV/H2O2/ZrO2 processes’ output, the sampling was carried out within 5–60-min retention times of the experiment in the entire study.
To segregate the catalyst particles from the solution, the samples were centrifuged (3 min in 5000 rpm) and then filtered in 0.22-μm filter papers. UV–Vis spectrophotometer device (Perkin-Elmer Lambda 25) was employed to assess the concentration of the residual furfural at 228 nm (Cuevas et al. 2014). Then, the standard curves were delineated for various concentrations so that the equivalent concentration of each absorption process can be determined (Borghei and Hosseini 2008). COD assessment was also carried out based on chromometry in a spectrometer device.
To compare the processes, besides the two above-mentioned processes, UV alone conditions, UV/H2O2 and ZrO2/H2O2, as well, were evaluated in furfural degradation process. The data were analyzed by the use of SPSS and Excel.
Results and discussion
The effect of pH on the efficiency of furfural removal in UV/ZrO2 and UV/H2O2/ZrO2 processes
Generally, it can be stated that the furfural removal efficiency decreases with the creation of more basic conditions. There was a significant correlation found between pH and UV/ZrO2 process in 60 min after the reaction initiation (P < 0.01). One reason behind such an increase in efficiency in lower pHs is that the ZrO2 nanocatalyst surface becomes positively charged and absorbs furfural as a result of which more furfural is absorbed, OH• is produced, the decomposition becomes more intensified in acidic environment, and then the removal efficiency increases eventually. Also, in UV/H2O2/ZrO2 process, H2O2 acts as the dominant oxidizing agent in the environment and the hydroxyl radical produced resultantly will display a higher oxidation potential. But, in basic environments, the nanocatalyst becomes negatively charged on its surface as a result of which absorption is reduced and then less OH• is produced. The results of the present study were similar to what was found by Malakootian et al. (2013). They studied the efficiency of UV/ZrO2 and UV/H2O2/ZrO2 processes in elimination of cyanide, and the highest removal efficiency found in pH values was equal to 4 and 8. Also, the results of the present study are consistent with what was found by Samarghandi et al. who studied photocatalytic decomposition of cyanide by the use of TiO2 as well as pentachlorophenol elimination by the use of UV/H2O2/ZrO2 process (Malakootian et al. 2013; Samarghandi et al. 2015). The optimal pH values in UV/ZrO2 and UV/H2O2/ZrO2 processes were 3 and 7, respectively.
The effect of zirconia nanoparticles on furfural removal efficiency in UV/ZrO2 and UV/H2O2/ZrO2 processes
The reason why the number of absorbed photons is increased with the initial increase in the nanoparticle’s concentration from 0.1 to 0.25 g/L has been the increase in the number of available activated sites as a result of which more furfural molecules are absorbed. Furthermore, the reason behind the lower furfural removal efficiency in a concentration of 1 g/L as compared with the concentrations 0.25 g/L and 0.5 g/L is that the increase in catalyst can even reduce the light infiltration to the solution and increase the light scattering of the nanoparticle surface that results in the reduction in the light-activated volume of the nanoparticle (Yang et al. 2008; Kashif and Ouyang 2009; Mahvi et al. 2009; Abdoallahzadeh et al. 2016), following which a small amount of ZrO2 is activated. The study by Chan et al. as well as the study by Parastar et al. on the nitrate removal in a ZnO/UV process also confirms this same finding of the present study (Chun et al. 2000; Mahvi et al. 2009; Biglari et al. 2015). But, in the study conducted by Samarghandi et al., it was shown that the pentachlorophenol removal efficiency reduces in UV/ZrO2/H2O2 process with the increase in catalyst amount from 0.1 to 1 g/L (Samarghandi et al. 2015). Therefore, the present study introduces 0.25 g/L as the optimal amount of the catalyst for performing the experiment.
The effect of hydrogen peroxidation amount addition on the furfural removal efficiency of UV/H2O2/ZrO2 process
The effect of furfural concentration on furfural removal efficiency in UV/ZrO2 and UV/ZrO2/H2O2 processes
Comparing the efficiency of UV irradiation and UV/H2O2 and ZrO2/H2O2 processes in furfural removal
Under the conditions of H2O2 and ZrO2 combination, furfural removal efficiency attained was 4–7%. At this stage, due to the absence of UV irradiation and resultant lack of valence band electron activation and the lack of active holes formation on ZrO2 photocatalyst surface as well as due to the lack of H2O2 photolysis and eventually for such a reason as the lack of hydroxyl radical’s generation, as the main agent contributing to the contaminant decomposition, the removal efficiency reached to its least possible value.
Comparing the efficiency of UV/ZrO2 and UV/H2O2/ZrO2 in removing dissolved COD
The results of the present study indicated that the highest efficiencies were, respectively, obtained for UV/H2O2/ZrO2, UV/H2O2, ZrO2/H2O2, UV irradiation and UV/ZrO2. UV alone, inter alia the performed stages, was found to have a small effect in furfural removal, and ZrO2/H2O2 process efficiency was very trivial. The highest removal output, about 99%, was obtained by UV/H2O2/ZrO2 process for a furfural concentration of 20 mg/L. The removal efficiency was somewhat increased with the increase in the dosage of the photocatalyst used as well as the increase in the H2O2 added which subsequently followed by a reduction; thus, the optimal conditions of the experiments were considered as stated in the following words: pH 7, H2O2 0.75 mg/L and catalyst dosage 0.25 g/L. The relationship between pH and furfural concentration in UV/ZrO2 process and the relationship between the reaction time and removal efficiency in UV/ZrO2 and UV/H2O2/ZrO2 process were found statistically significant. It can be finally stated that the hydrogen peroxide in combination with zirconium nanoparticle can be utilized as an effective method in furfural removal. Of course, it has to be pointed out that there is a need for pretreatment in higher furfural concentrations of industrial wastewaters before employing the above-described method so as to decrease furfural concentration in which case the aforementioned processes can promise a high efficiency in furfural removal.
The authors would like to gratefully acknowledge the financial support by the research center of Hamadan University of Medical Sciences, Iran.
The study was funded by Vice-chancellor for Research and Technology, Hamadan University of Medical Sciences (No. 9310235297).
- Abdoallahzadeh H, Alizadeh B, Khosravi R, Fazlzadeh M (2016) Efficiency of EDTA modified nanoclay in removal of humic acid from aquatic solutions. J Mazandaran Univ Med Sci 26(139):111–125Google Scholar
- Azizl E, Fazlzadeh M, Ghayebzadeh M et al (2017) Application of advanced oxidation process (H2O2/UV) for removal of organic materials from pharmaceutical industry effluent. Environ Prot Eng 43(1):183–191Google Scholar
- Biglari H, Sajjadi S, Javan N, Mirzabeigi M, Afsharnia M (2015) Removal of water soluble phenol by simultaneous using of UV radiation and ZnO. Q Horizon Med Sci 21(Special Issue):33–41Google Scholar
- Fazlzadeh M, Abdoallahzadeh H, Khosravi R, Alizadeh B (2016a) Removal of acid black 1 from aqueous solutions using Fe3O4 magnetic nanoparticles. J Mazandaran Univ Med Sci 26(143):174–186Google Scholar
- Fazlzadeh M, Ahmadfazeli A, Entezari A, Shaegi A, Khosravi R (2016b) Removal of cephalexin using green montmorillonite loaded with TiO2 nanoparticles in the presence potassium permanganate from aqueous solution. Koomesh 18(3):388–396Google Scholar
- Fazlzadeh M, Rahmani K, Zarei A, Abdoallahzadeh H, Nasiri F, Khosravi R (2017b) A novel green synthesis of zero valent iron nanoparticles (NZVI) using three plant extracts and their efficient application for removal of Cr(VI) from aqueous solutions. Adv Powder Technol 28:122–130CrossRefGoogle Scholar
- Hoydonckx H, Van Rhijn W, Van Rhijn W, De Vos D, Jacobs P (2000) Furfural and derivatives. In: Ullmann’s encyclopedia of industrial chemistry. Wiley, WeinheimGoogle Scholar
- Kamat PS, Huehn R, Nicolaescu R (2008) Semiconductor nanostructures for simultaneous detection and degradation of organic contaminants in water. J Photochem Photobiol Chem 42:573–577Google Scholar
- Malakootian M, Hashemi Cholicheh M (2012) Efficacy of photocatalytic processes using silica and zirconia nanoparticles in the bivalent nickel removal of aqueous solutions and determining the optimum removal conditions. J Mazandaran Univ Med Sci 22(93):87–96Google Scholar
- Malakootian M, Dowlatshahi S, Hashemi Cholicheh M (2013) Reviewing the photocatalytic processes efficiency with and without hydrogen peroxide in cyanide removal from aqueous solutions. J Mazandaran Univ Med Sci 23(104):69–78Google Scholar
- Parastar S, Nasseri S, Mahvi AH, Gholami M, Javadi AH, Hemmati S (2012) Photocatalytic reduction of nitrate in aqueous solutions using Ag-doped TiO2/UV process. Iran J Health Environ 5(3):307–318Google Scholar
- Samarghandi M, Siboni M, Maleki A, Jafari SJ, Nazemi F (2011) Kinetic determination and efficiency of titanium dioxide photocatalytic process in Removal of Reactive Black 5 (RB5) dye and cyanide from aquatic solution. J Mazandaran Univ Med Sci 21(81):44–52Google Scholar
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.