An experimentally validated CFD model was developed for lab-scale arsenic (As) fixed-bed columns using COMSOL Multiphysics. The effects of key factors such as the adsorbent bed depth, the feed flow rate, and the initial As concentration (conc.) on the overall As removal performance were investigated. Subsequently, the CFD was combined with response surface methodology (RSM) to optimize process conditions and examine main and interaction effects of these factors on model responses, i.e., the As removal efficiency and the bed saturation time. The ANOVA results suggested that quadratic regression models were highly significant for both responses. The established regression model equations predicted the response values closer to CFD measurements. It was found that, compared with the initial As conc. and the feed flow rate, the effect of the bed depth was more significant. Moreover, both the As removal efficiency and the bed saturation time were increased reasonably with the increasing bed depth and decreased with the increasing feed flow rate and initial As conc. The optimum conditions for the As removal process were obtained as the bed height of 80 cm, the initial As concentration of 2.7 mmol/m³, and the feed flow rate of 1 L/min. The present combined CFD−RSM approach is a useful guideline in overall design and optimization of various lab-scale and industrial applications for removal of As from wastewater.

The importance of statistical modeling is obvious because it imparts an imperative role in predicting the effects of significant factors on any experimental process. In recent days, ELMs (Emulsion Liquid Membranes) are considered as an effective technique for the treatment of industrial wastewater. Despite of many advantages over the other treatment methods, ELM technology encounters one serious drawback of the stability of emulsion. The subject of this research is to identify the factors which are important to study the stability of ELM and also to evaluate the response of these parameters on stability. The membrane used in this study consisted of Span-80 and Hexane as surfactant and diluent respectively. The internal aqueous phase was H2SO4. The experimental setup was designed by using a well-known statistical approach of DoE (Design of Experiment) and the data was analyzed by Taguchi Method using a fractional factorial design. All the parameters including aqueous phase concentration, surfactant concentration, volume ratio of organic to aqueous phase, emulsification speed and emulsification time were selected as key factors to study their effect on the stability of ELM. Using different statistical techniques, it was found that emulsification speed and volume ratio of organic to aqueous phase are two most significant parameters. The significance level of these factors i.e. emulsification speed and volume ratio of organic to aqueous phase was statistically found as 99.7 and 99.9% respectively. A statistical model was also developed and the experimental results were compared with estimated results. The value of correlation coefficient, R2 was calculated as 0.997 indicating that the developed model fits the data very well.

The work focuses on the removal of Arsenic-III (As(III)) from water sample by an indigenous iron ore from Balochistan by adsorption method. Three iron ore samples were analyzed by X-Ray Diffractometer (XRD) and a sample from Shikarap containing iron 36.2% was selected because it contained the highest amount of hematite. The batch study was conducted to examine the adsorption by iron ore and maximum adsorption was observed at pH 6, 1/2 g dose per 50 mL solution, contact time 2 hr and shaking speed 150 rpm. At the optimized conditions, the removal was 89% when monitored at 50μg L-1 initial concentration of arsenic. The arsenic removal was monitored by Atomic Absorption Spectrometer (AAS) using hydride generation. Dubinin - Radushkevich (D-R), Freundlich and Langmuir's isotherms were examined. The highest adsorption capacityof iron ore for As(III) removal was observed 13.67 μg g-1 by Langmuir model and Freundlich isotherm indicated good adsorption intensity with value n = 1.512. Thermodynamic parameters revealed that adsorption was exothermic and physisorption. The Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray (EDX)techniques were applied to scan the surface morphology and the percentage elemental composition of samples respectively. SEM results demonstrated that Shikarap mineral grains are an oval shape and these were changed after the uptake of As(III). The EDX spectra of Shikarap mineral confirm the As(III) adsorption on particles as As 4.19%.