Continuous cadmium removal from aqueous solutions by seaweed in a packed-bed column under consecutive sorption-desorption cycles

Abstract

Packed-bed column process efficiency for cadmium adsorption from aqueous solution was investigated under different bed heights (2.6 to 7.5 cm) and feed flow rates (15 to 30 ml min −1 ). The column was filled with brown seaweed, Sargassum angustifolium. Three simplified models, including Bed Depth Service Time, Thomas, and YoonNelson were employed for describing the experimental breakthrough curves as well as achieving design parameters. Bed lifetime was also evaluated in several consecutive sorption-desorption cycles. Cadmium concentration of 0.005 mg l −1 , as a standard limit for potable water, was considered as the breakthrough concentration. The maximum column performance was achieved 81% at 7.5 cm bed length and flow rate of 15 ml min −1 . Indeed, increasing the bed height increased the sorption performance and service time, while increasing the feed flow rate had a negative effect. Maximum sorption capacity value remained almost constant by the bed height changes; however, increase in the feed flow rate slightly decreased it. The modeling results revealed that the Yoon-Nelson model was more accurate than Thomas for describing the experimental breakthrough data, especially at low flow rates. Column service time predictions were surprisingly achieved using the Bed Depth Service Time model even at extrapolations. 20% reduction in column adsorption efficiency was observed at the end of four consecutive sorption-desorption cycles; however, desorption efficiencies were achieved more than 99% in each cycle.

Hexavalent chromium removal and total chromium biosorption from aqueous solution by Quercus crassipes acorn shell in a continuous up-flow fixed-bed column: Influencing parameters, kinetics, and mechanism

“…A Pyrex glass cylindrical column with an internal diameter of 1.2 cm and a height of 15.5 cm was employed in the column experiments. It is well known that wall effects can influence the shape of the biosorption breakthrough curves for fixed-bed systems and that for avoiding such effects it is recommended that the ratio of column diameter (D C ) to particle diameter (D p ) be greater than 10 [20]. The present study complied with this recommendation.…”

“…Modeling the biosorption breakthrough curve is crucial for deriving characteristic or design parameters that can be used to describe the breakthrough curve for given experimental conditions as well as to predict the breakthrough curve behavior for scale-up purposes and performance comparisons [20,27]. In this work, the Thomas, Bohart-Adams, Yan, dose-response and Yoon-Nelson models were fitted to the data from the dynamic flow experiments performed in the fixed-bed column to predict the breakthrough curves obtained at different influent Cr(VI) solution pH values, influent Cr(VI) concentrations, biosorbent bed heights, and influent flow rates as well as to determine the characteristic parameters of the column.…”

“…& Bonpl. ; RMSE, root mean squared error; SSE, sum of squared errors; XPS, X-ray photoelectron spectroscopy.. operation, low cost, and capacity to be scaled up from a laboratory process and produce effluents of higher quality [16,19,20].…”

Batch and Packed Bed Column Study for the Removal of Cr (VI) and Ni (II) Using Agro-Industrial Wastes

“…The lowest adsorption values were obtained using YSR at 40 • C/3 cm and 55 • C/1.5 cm, respectively, with an efficiency of 81%. It is also evident that the bed height has a direct influence, thus favoring the adsorption efficiency of Ni (II) present in the solution; this is because the greater the amount of adsorbent in the column, the more binding sites are available, thus expanding the mass transfer zone [74]. When the bed height is low, axial dispersion phenomena predominate during mass transfer, which reduces the residence time and the rate of diffusion of ions from the solution to the adsorbent [73].…”

Highly Effective Removal of Tetracycline from Water by Hierarchical Porous Carbon: Batch and Column Adsorption

“…The BDST model is usually adopted to predict the relationship between the bed depth of an adsorption column and the service time. The mathematical expression is shown in the following equation 42…”