Analysis and modeling of fixed bed column operations on flumequine removal onto activated carbon: pH influence and desorption studies

Pre-concentration of nalidixic acid through adsorption–desorption cycles: Adsorbent selection and modeling

“…This behavior contrasts with the favorable adsorption isotherms observed for this adsorbate on the studied adsorbents [42], especially for GF-40 and MWCNT; since, it is expected that favorable adsorption isotherms leads to sharper mass transfer areas into the column. Thus, as it was already observed by other authors, the concentration gradients in batch and continuous flow systems are different [31]. At this point, the adsorption process on porous solids can be split into three stages: (a) external mass transfer of the adsorbate through the liquid film to the external surface of the adsorbent (outer diffusion); (b) transport of the adsorbate from the exterior surface of the adsorbent to the pores of the internal structure of the adsorbent (intra-particle diffusion or inner diffusion); and (c) adsorption of the adsorbate onto the active sites on the inner and outer surfaces of the adsorbent [43].…”

“…At this point, the adsorption process on porous solids can be split into three stages: (a) external mass transfer of the adsorbate through the liquid film to the external surface of the adsorbent (outer diffusion); (b) transport of the adsorbate from the exterior surface of the adsorbent to the pores of the internal structure of the adsorbent (intra-particle diffusion or inner diffusion); and (c) adsorption of the adsorbate onto the active sites on the inner and outer surfaces of the adsorbent [43]. Generally, the adsorption process is controlled by either the first or the second step, or a combination of both [44,45], and from the observed results, it is important to point out that activated carbon is the most microporous material (Table 2), thus the diffusion of NAL from the bulk liquid to the mesopores and then into the micropores could take a longer time, leading to slower adsorption kinetics [31]. This internal diffusion can also explain the different shapes of the breakthrough curves for the three adsorbents, since the GF-40 curves exhibit the most early breakthrough and tailing.…”

“…The adsorption capacities at breakthrough time (q bk for C/C 0 =0.05 [31]) and at saturation time (q s for the maximum C/C 0 obtained) were calculated the according to the Gaenkoplis' model [46]. 8 where C and C 0 are the NAL effluent and inlet concentration (mg/L); Q, the volumetric flow rate (L/h); W, the mass of adsorbent (g); and, t s and t bk , the saturation and breakthrough times respectively (h).…”

“…It presents several advantages: simple design and operation, low initial cost, and high potential for the removal of emerging pollutants due to the vast variety of adsorbents [27][28][29]. Activated carbons are effective to remove antibiotics from water, significant adsorption capacities being reported in the literature [30][31][32]. But for adsorption process, the possibility of regeneration, allowing the use of the adsorbent in subsequent adsorption-desorption cycles, is as important as the adsorption capacity [33].…”

Adsorption of Phenol from Aqueous Solution Using Lantana camara, Forest Waste: Packed Bed Studies and Prediction of Breakthrough Curves

“…This was due to the fact that with increasing bed height, more binding sites are available for adsorbate to diffuse through the pores of the adsorbent and the adsorption area increases (Tamez Uddin et al 2009;Lezehari et al 2012;Gupta and Babu 2009;Baral et al 2009). The breakthrough time in shorter bed is generally lower and complete utilization of the bed may not be possible (Sotelo et al 2013b). Considering the adsorption capacity and the other results at different bed heights, 10 cm bed height was selected for further experiments.…”