This work aims to investigate the ability of using waste foundry sand (WFS) resulting as inexpensive by-product from steel industry in the low permeability barrier (LPB) and permeable reactive barrier (PRB) technologies for restriction of the movement of lead and nickel ions in the groundwater. Outputs of flask and tank tests certified that this material could capture these ions with sorption efficiency greater than 95% at time, pH, sorbent dosage, and speed equal to 60 min, 4 for lead and 6 for nickel, 2.5 g/100 mL, and 250 rpm, respectively. Sorption isotherm measurements were represented in a good manner by Langmuir model in comparison with Freundlich model with coefficient of determination (R2) greater than 0.99. So, the chemisorption was the predominant mechanism which could be supported by O-H, H-O-H, C-O, O-Si-O, and Si-O functional groups based on the Fourier transform infrared analysis. The maximum sorption capacity of WFS was 13.966 and 4.227 mg/g for lead and nickel ions, respectively, with corresponding affinities equal to 0.647 and 0.099 L/mg. Measurements signified that the hydraulic conductivity of WFS was 3.8 × 10−7 cm/s which satisfies the requirements of LPB. To obtain the acceptable values of permeability and reactivity, PRB was prepared from mixing 18% WFS with 82% filter sand. COMSOL software was able to simulate the measurements of two-dimensional tank packed with Iraqi soil aquifer in combination with WFS-LPB and WFS-filter sand PRB. Thicker barriers have a high ability in the protection of locations in the down-gradient side because their longevity increased dramatically with increase of barrier thickness.
An integrated linear regression technique was developed and validated to model dissolved oxygen in salt lakes by using R software and based on data from Sawa Lake, Iraq. The technique helps understand and evaluate salty aquatic ecosystems in the presence of water quality data gaps. The technique involved selecting the important water quality parameters that have significant statistical relationship with dissolved oxygen. In order to make the regression development simpler, the validation approach was incorporated with the model. Linearity, homogeneity, normality, outliers, and influential data points were verified. The simulation approach was also capable of displaying the interaction between the selected water quality parameters and the other insignificant parameters. The statistical analysis results indicated that dissolved oxygen in salt lakes is a function of total dissolved solids. The developed model represented dissolved oxygen with R-squared of 90.73% and p-value of 1.08E-06. Furthermore, the model results showed that the influence of salty ions on dissolved oxygen/total dissolved solids model is the same. It was found that temperature has a significant impact on the developed dissolved oxygen model. In addition, the model simulation revealed that salt melting surrounding the lake due to temperature variation during the year cycle
Ionic mass transfer in a novel electrocoagulation reactor (ECR) using a rotating impeller anode is studied experimentally using the limiting current density method. The CFD simulation is also conducted for characterizing the novel electrocoagulation reactor (ECR) and validating the experimental study of ionic mass transfer. Variables included rotational speed and anode diameter. The Bland-Altman method was used to verify the accuracy of experimental and simulation results. Data for the condition 11852 < Re < 58550 and 88 < Sc < 285 were found to fit the equation for the largest diameter of 11.2 cm; Sh = 2.1Re0.93Sc0.33. Based on COD removal efficiency, optimal EC performance is realized at the largest anode diameter of 11.2 cm, confirming the enhancement of aluminum mass transfer by increasing the anode diameter. The experimental values of current density and mass transfer coefficient are validated by CFD simulation for all the rotational speeds and anode diameters. The accuracy is up to 95% for the experimental current densities compared with simulation values.
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