Optimization of electrocoagulation process to treat biologically pretreated bagasse effluent

The main objective of the present study was to investigate the efficiency of electrocoagulation process as a post-treatment to treat biologically pretreated bagasse effluent using iron electrodes. The removal of chemical oxygen demand (COD) and total suspended solids (TSS) were studied under different operating conditions such as amount of dilution, initial pH, applied current and electrolyte dose by using response surface methodology (RSM) coupled with four-factor three-level Box-Behnken experimental design (BBD). The experimental results were analyzed by Pareto analysis of variance (ANOVA) and second order polynomial mathematical models were developed with high correlation of efficiency (R2) for COD, TSS removal and electrical energy consumption (EEC). The individual and combined effect of variables on responses was studied using three dimensional response surface plots. Under the optimum operating conditions, such as amount of dilution at 30 %, initial pH of 6.5, applied current of 8 mA cm-2 and electrolyte dose of 740 mg l-1 shows the higher removal efficiency of COD (98 %) and TSS (93 %) with EEC of 2.40 Wh, which were confirmed by validation experiments

Preparation and optimization of macroalgae-derived solid acid catalysts

Solid acid catalysts were synthesized from macroalgae Sargassum horneri via hydrothermal carbonization followed by sulfuric acid sulfonation. A three-variable Box-Behnken design and optimization was used to maximize surface acidity. The optimal preparation conditions were found to be at the carbonization temperature of 217 °C, the carbonization time of 4.6 h and the sulfonation temperature of 108.5 °C. Under these conditions, the highest surface acidity achieved was 1.62 mmol g−1. Physical and chemical properties of prepared solid acid catalyst were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, and elemental analysis. The results proved the grafting of –SO3H groups on an amorphous carbon structure. The catalyst activity was evaluated by the esterification of oleic acid with methanol. The sample prepared achieved 96.6% esterification yield, which was higher than the 86.7% yield achieved by commercial Ambersyst-15 under the same reaction conditions

Dental caries in primary and permanent teeth in children's worldwide, 1995 to 2019: a systematic review and meta-analysis

Background: Early childhood caries (ECC) is a type of dental caries in the teeth of infants and children that is represented as one of the most prevalent dental problems in this period. Various studies have reported different types of prevalence of dental caries in primary and permanent teeth in children worldwide. However, there has been no comprehensive study to summarize the results of these studies in general, so this study aimed to determine the prevalence of dental caries in primary and permanent teeth in children in different continents of the world during a systematic review and meta-analysis. Methods: In this review study, articles were extracted by searching in the national and international databases of SID, MagIran, IranMedex, IranDoc, Cochrane, Embase, ScienceDirect, Scopus, PubMed, and Web of Science (ISI) between 1995 and December 2019. Random effects model was used for analysis and heterogeneity of studies was evaluated by using the I2 index. Data were analyzed by using the Comprehensive Meta-Analysis (Version 2) software. Findings: In this study, a total of 164 articles (81 articles on the prevalence of dental caries in primary teeth and 83 articles on the prevalence of dental caries in permanent teeth) were entered the meta-analysis. The prevalence of dental caries in primary teeth in children in the world with a sample size of 80,405 was 46.2% (95% CI: 41.6–50.8%), and the prevalence of dental caries in permanent teeth in children in the world with a sample size of 1,454,871 was 53.8% (95% CI: 50–57.5%). Regarding the heterogeneity on the basis of meta-regression analysis, there was a significant difference in the prevalence of dental caries in primary and permanent teeth in children in different continents of the world. With increasing the sample size and the year of study, dental caries in primary teeth increased and in permanent teeth decreased. Conclusion: The results of this study showed that the prevalence of primary and permanent dental caries in children in the world was found to be high. Therefore, appropriate strategies should be implemented to improve the aforementioned situation and to troubleshoot and monitor at all levels by providing feedback to hospitals

Bagasse wastewater treatment using biopolymer: A novel approach

In this present study, the removal of turbidity, biological oxygen demand (BOD) and chemical oxygen demand (COD) were investigated under different operating conditions such as agitation time (X1: 15-25 min), initial pH (X2:4-8), chitosan dose (X3:1.2-2 g L-1) and settling time (X4:40-80 min) to treat bagasse based paper and pulp industry wastewater via response surface methodology (RSM). The experimental data obtained were fitted to a second-order polynomial equation using multiple regression analysis and ANOVA (analysis of variance) was used to examine the significance of the developed mathematical models. The 3-D response surface plots were derived from the mathematical models in order to study the interactive effects process variables on the treatment efficiency. Derringer’s desired function methodology were applied to determine the optimal conditions and it was found to be: agitation time of 20 min, initial pH of 6, chitosan dose of 1.8 gL-1 and settling time of 60 min. Under these conditions, the removal of turbidity, BOD and COD were found to be 84 %, 90 % and 93 % respectively