Abstract
The present work reports the performance of three types of polyethersulfone (PES) membrane in the removal of highly polluting and toxic lead Pb2+ and cadmium Cd2+ ions from a single salt. This study investigated the effect of operating variables, including pH, types of PES membrane, and feed concentration, on the separation process. The transport parameters and mass transfer coefficient (k) of the membranes were estimated using the combined film theory-solution-diffusion (CFSD), combined film theory-Spiegler-Kedem (CFSK), and combined film theory-finely-porous (CFFP) membrane transport models. Various parameters were used to estimate the enrichment factors, concentration polarization modulus, and Péclet number. The pH values significantly affected the permeation flux of the Pb2+ solution but only had a slight effect on the Cd2+ solution. However, Cd2+ rejection was highly improved by increasing the pH value. The rejection of the PES membranes increased greatly as the heavy metal concentration rose, while the heavy metal concentration moderately affected the permeation flux. The maximum rejection of Pb2+ in a single-salt solution was 99%, 97.5%, and 98% for a feed solution containing 10 mg Pb/L at pH 6, 6.2, and 5.7, for PES1, PES2, and PES3, respectively. The maximum rejection of Cd2+ in single-salt solutions was 78%, 50.2%, and 44% for a feed solution containing 10 mg Cd/L at pH 6.5, 6.2, and 6.5, for PES1, PES2, and PES3, respectively. The analysis of the experimental data using the CFSD, CFSK, and CFFP models showed a good agreement between the theoretical and experimental results. The effective membrane thickness and active skin layer thickness were evaluated using the CFFP model, indicating that the Péclet number is important for determining the mechanism of separation by diffusion.
Highlights
In the past few years, attention has been concentrated on the removal of heavy metal ions from wastewater due to their toxicity, and their impact on human health
The reason behind selected different PES hollow fibers was to find the optimum specifications of the hollow fibers in the range located between NF and UF membranes that was applied for highly efficient heavy metal removal with high permeate flux
This study investigated the models’ validity and the type of fitting used by calculating the nonlinear parameters expressed by Equation (28) [46]: S2 =
Summary
In the past few years, attention has been concentrated on the removal of heavy metal ions from wastewater due to their toxicity, and their impact on human health. Various traditional processes have been employed to remove heavy metals from effluents, such as chemical precipitation, electrocoagulation, solvent extraction, ion exchange, and adsorption on various sorbents, etc. Most of these above-mentioned processes suffer from economic limitations and other disadvantages. Both adsorption and ion exchange are inexpensive and highly effective for treating low concentrations of heavy metals; they generate hazardous sludge that requires regeneration or additional treatment, such as solidification. Solvent extraction and chemical precipitation are considered to be polluting processes themselves [2,3,4,5,6,7,8,9,10,11,12]
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