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Abstract
Column studies were performed to determine the effect of bed height, linear flow rate, adsorbent particle size and initial metal ion concentration on lead removal by keramzite sand coated with electroplating sludge. The Bed depth service time (BDST) model applied to the data at 2% breakthrough gave the best approximation to the experimental results compared with other investigated breakthrough points. The adsorption performance of the thermally modified coated keramzite columns could be well described by the Wolborska model up to 50% breakthrough point. The application of this model allowed determination of the kinetic coefficients of external mass transfer in the fixed bed and the time for protective action of the sorbent layers. The experimental results support the assumption that the external mass transfer of the solute through the hydrodynamic boundary layer is the rate-limiting step. It has been established that the keramzite sand coated with electroplating sludge (particle size 0.5–0.8 mm) can be successfully used for lead removal from dilute metal ion solutions at linear flow rate 4–6 cm/min and empty bed contact time ≥ 3 min.