The Dynamic Behaviour of a Binary Adsorbent in a Fixed Bed Column for the Removal of Pb2+ Ions from Contaminated Water Bodies

Abstract

In the search for a technically efficient and abundant adsorbent in water treatment processes, a bio-composite adsorbent derived from agricultural wastes has been identified as a potential candidate. In this study, eggshells and sugarcane bagasse were combined in varied proportions (1:0, 1:3, 1:1, 3:1 and 0:1) and applied as biosorbents in a lab-scale adsorption column. The effect of bed depth (4–12 cm) of the biosorbents was investigated which enabled the prediction of breakthrough curves for the removal of Pb (II) ions. The life span of the column was extended by increasing the bed depth of the column. The binary adsorbent of 1:3 weight ratio of <75 µm particle size showcased the highest removal efficiency of 91% at a bed depth of 12 cm. The mass transfer zone (MTZ) increased with increasing bed depth with a minor portion of the bed left unused, signifying that the process was highly efficient. The Thomas model constant, KTh, decreased with increasing bed depth with the maximum amount of Pb adsorbed being 28.27 mg/g. With the Yoon–Nelson model, KYN decreased with an increase in τ as the bed height increased. In this study, a novel approach was adopted where the proposed methodology enabled the use of a bio-composite adsorbent in heavy metal removal. The findings of this research will aid in the design and optimisation of the pilot-scale operation of environmentally friendly treatment options for metal laden effluent.

Removal of Diclofenac and Heavy Metal Ions from Aqueous Media Using Composite Sorbents in Dynamic Conditions

“…This extension of MTZ leads to the elongation of the breakthrough curve, accompanied by a reduction in sorption capacity. Lower MTZ values indicate low mass transfer resistance and a correspondingly limited axial dispersion [ 43 ].…”

“…The sorption efficacy of the composite materials was evaluated by using the mass transfer zone (MTZ) concept, which denotes the length of the adsorption zone in the column and which is calculated according to Equation (2) [ 43 ]: where Z represents the height of the composite material bed within the column, while t b and t s correspond to the breakthrough and saturation times, respectively.…”

“…The sorption efficacy of the composite materials was evaluated by using the mass transfer zone (MTZ) concept, which denotes the length of the adsorption zone in the column and which is calculated according to Equation (2) [43]:…”

“…This extension of MTZ leads to the elongation of the breakthrough curve, accompanied by a reduction in sorption capacity. Lower MTZ values indicate low mass transfer resistance and a correspondingly limited axial dispersion [43]. The assessment of fixed-bed sorption column performance relies on the analysis of breakthrough curves, which involve the calculation of key parameters [46,47] like the breakthrough time (t b ) and breakthrough volume (V b ), representing the moment when the effluent concentration reaches 10% of the initial concentration (C t /C 0 = 0.1).…”

“…This extension of MTZ leads to the elongation of the breakthrough curve, accompanied by a reduction in sorption capacity. Lower MTZ values indicate low mass transfer resistance and a correspondingly limited axial dispersion [43]. Note: V b , mL-breakthrough volume; t b , min-breakthrough time; V s , mL-saturation volume; t s , minsaturation time; q dyn mg/g-adsorption capacity in dynamic conditions; MTZ-mass transfer zone.…”