Abstract:Absorption of nitric oxide from nitric oxide /air mixture in hydrogen peroxide solution has been studied on bench scale internal loop airlift reactor. The objective of this investigation was to study the performance of nitric oxide absorption in hydrogen peroxide solution in the airlift reactor and to explore/determine the optimum conditions using response surface methodology. A BoxBehnken model has been employed as an experimental design. The effect of three independent variables-namely nitric oxide gas veloc… Show more
“…The high coefficients of determination R 2 of 0.974 and 0.967, respectively, also indicated the adequate ability of the model to represent the actual relationship among the operating variables (Bashir et al, 2010; Naik and Setty, 2014; Subramonian et al, 2015). The predicted R 2 values of 0.844 and 0.809 were in desirable and reasonable agreement with the adjusted R 2 of 0.942 and 0.926, respectively, indicating the aptness of the experimental model within the range of operating variables (Bhanarkar et al, 2014).…”
The widespread distribution of persistent organic pollutants (POPs) in landfill leachate is problematic due to their acute toxicity, carcinogenicity and genotoxicity effects, which could be detrimental to public health and ecological systems. The objective of this study was to evaluate the effective removal of POPs - namely, p-tert-Butylphenol and Pyridine, 3-(1-methyl-2-pyrrolidinyl)-, (S)- - from landfill leachate using locust bean gum (LBG), and in comparison with commonly used alum. The response surface methodology coupled with a Box-Behnken design was employed to optimize the operating factors for optimal POPs removal. A quadratic polynomial model was fitted into the data with the R values of 0.97 and 0.96 for the removal of p-tert-Butylphenol and Pyridine, 3-(1-methyl-2-pyrrolidinyl), (S)-, respectively. The physicochemical characteristics of the flocs produced by LBG and alum were evaluated with Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM). The infrared spectra of LBG-treated floc were identical with LBG powder, but there was some variation in the peaks of the functional groups, signifying the chemical interactions between flocculants and pollutant particles resulting from POPs removal. The results showed that p-tert-Butylphenol and Pyridine, 3-(1-methyl-2-pyrrolidinyl)-, (S)- obtained 96% and 100% removal using 500 mg/L of LBG at pH 4. pH have a significant effect on POPs removal in leachate. It is estimated that treating one million gallons of leachate using alum (at 1 g/L dosage) would cost US$39, and using LBG (at 500 mg/L dosage) would cost US$2. LBG is eco-friendly, biodegradable and non-toxic and, hence, strongly recommended as an alternative to inorganic coagulants for the treatment of POPs in landfill leachate.
“…The high coefficients of determination R 2 of 0.974 and 0.967, respectively, also indicated the adequate ability of the model to represent the actual relationship among the operating variables (Bashir et al, 2010; Naik and Setty, 2014; Subramonian et al, 2015). The predicted R 2 values of 0.844 and 0.809 were in desirable and reasonable agreement with the adjusted R 2 of 0.942 and 0.926, respectively, indicating the aptness of the experimental model within the range of operating variables (Bhanarkar et al, 2014).…”
The widespread distribution of persistent organic pollutants (POPs) in landfill leachate is problematic due to their acute toxicity, carcinogenicity and genotoxicity effects, which could be detrimental to public health and ecological systems. The objective of this study was to evaluate the effective removal of POPs - namely, p-tert-Butylphenol and Pyridine, 3-(1-methyl-2-pyrrolidinyl)-, (S)- - from landfill leachate using locust bean gum (LBG), and in comparison with commonly used alum. The response surface methodology coupled with a Box-Behnken design was employed to optimize the operating factors for optimal POPs removal. A quadratic polynomial model was fitted into the data with the R values of 0.97 and 0.96 for the removal of p-tert-Butylphenol and Pyridine, 3-(1-methyl-2-pyrrolidinyl), (S)-, respectively. The physicochemical characteristics of the flocs produced by LBG and alum were evaluated with Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM). The infrared spectra of LBG-treated floc were identical with LBG powder, but there was some variation in the peaks of the functional groups, signifying the chemical interactions between flocculants and pollutant particles resulting from POPs removal. The results showed that p-tert-Butylphenol and Pyridine, 3-(1-methyl-2-pyrrolidinyl)-, (S)- obtained 96% and 100% removal using 500 mg/L of LBG at pH 4. pH have a significant effect on POPs removal in leachate. It is estimated that treating one million gallons of leachate using alum (at 1 g/L dosage) would cost US$39, and using LBG (at 500 mg/L dosage) would cost US$2. LBG is eco-friendly, biodegradable and non-toxic and, hence, strongly recommended as an alternative to inorganic coagulants for the treatment of POPs in landfill leachate.
“…The model had insignificant lack-of-fit values, which supported a strong model correlation between the operating conditions and COD removal. Additionally, R 2 value greater than 0.75 indicates the aptness of the model (Naik and Setty, 2014) and adjusted R 2 indicates the capability of the developed model to satisfactorily describe the system behaviour within the range of operating factors (Bhanarkar et al, 2014). In this study, the quadratic model was well-fitted to the experimental data with high R 2 and adjusted R 2 values (0.9966 and 0.9935, respectively).…”
Section: Rsm Modeling and Optimization Study On Photocatalysis Of Ppmementioning
In this work, heterogeneous photocatalysis was used to treat pulp and paper mill effluent (PPME). Magnetically retrievable FeO-TiO was fabricated by employing a solvent-free mechanochemical process under ambient conditions. Findings elucidated the successful incorporation of FeO into the TiO lattice. FeO-TiO was found to be an irregular and slightly agglomerated surface morphology. In comparison to commercial P25, FeO-TiO exhibited higher ferromagnetism and better catalyst properties with improvements in surface area (58.40 m/g), pore volume (0.29 cm/g), pore size (18.52 nm), and band gap (2.95 eV). Besides, reusability study revealed that FeO-TiO was chemically stable and could be reused successively (five cycles) without significant changes in its photoactivity and intrinsic properties. Additionally, this study demonstrated the potential recovery of FeO-TiO from an aqueous suspension by using an applied magnetic field or sedimentation. Interactive effects of photocatalytic conditions (initial effluent pH, FeO-TiO dosage, and air flow-rate), reaction mechanism, and the presence of chemical oxidants (HO, BrO, and HOCl) during the treatment process of PPME were also investigated. Under optimal conditions (initial effluent pH = 3.88, [FeO-TiO] = 1.3 g/L, and air flow-rate = 2.28 L/min), the treatment efficiency of FeO-TiO was 98.5% higher than the P25. Based on Langmuir-Hinshelwood kinetic model, apparent rate constants of FeO-TiO and P25 were 9.2 × 10 and 2.7 × 10 min, respectively. The present study revealed not only the potential of using magnetic FeO-TiO in PPME treatment but also demonstrated high reusability and easy separation of FeO-TiO from the wastewater.
“…As can be seen, R 2 value is high (R 2 =0.9955) and reasonably agreed with the adjusted R 2 value of 0.9872. It means that the quadratic model fits the data and satisfactorily describe the system behavior within the range of operating factors [30]. The observed and predicted values by the quadratic model are shown in Table 2.…”
Section: Modeling and Statistical Analysismentioning
Flocculants are widely used along with coagulant to increase the efficiency of coagulation-flocculation process for removal of colloidal particles from wastewaters. The most widely used flocculants are synthetic which have some problems such as non-biodegradability and release of toxic residual monomers. The main aim of this study is to evaluate the performance of cellulose sulfate (CS), which was synthesized through sulfonation of cotton, as a biodegradable and natural-based flocculant. Reaction time as an important factor in the sulfonation reaction was optimized for obtaining CS with high charge density and suitable fiber size. The sulfate content, charge density (CD) and morphology of each CS were determined to investigate and select the best CS for the flocculation process. A suspension containing kaolin clay was used as a colloidal test solution and coagulation was performed using alum (as a coagulant) and CS (as a flocculant). Optimization was performed using response surface methodology (RSM). The optimization results showed that CS had a good performance in turbidity reduction in coagulation-flocculation treatment and maximum turbidity reduction (98.9 %) was obtained at alum dosage of 23.1 mg/L, CS dosage of 7.2 mg/L and pH = 6.2. The results showed that the pH variation had insignificant effect on the CS dosage. Zeta potential measurements and microscopic photos of flocs confirm charge neutralization and bridge formation in flocculation using cellulose sulfate, respectively. Also, the total chemical consumption reduced compared with the use of alum alone. As a consequence, CS can be considered as a suitable alternative for conventional flocculants.
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