Synthesis and Characterization of Novel Uracil-Modified Chitosan as a Promising Adsorbent for Efficient Removal of Congo Red Dye

Abstract

Novel Uracil-modified chitosan (UCs) adsorbent has successfully been synthesized through a four-step method during which the amino groups of chitosan have been protected, then epoxy nuclei have been incorporated, afterwards the latter have been opened using 6-amino-1,3-dimethyl uracil, and finally the amino groups have been regained via removing the protection. Its structure was checked using FTIR, XRD and SEM techniques. The adsorption capacity of UCs for anionic Congo Red (CR) dye was studied under various conditions. It decreased significantly with increasing the solution pH value and dye concentration, while increased with increasing temperature. The adsorption of UCs for CR dye at different temperatures, solution pH and dye concentrations fitted to the kinetic model of pseudo-second order and Elovich model. The intraparticle diffusion model showed that the adsorption process involves multi-step process. The isotherm of CR dye adsorption by UCs conforms to the Langmuir isotherm model indicating the monolayer nature of adsorption. The maximum monolayer coverage capacity, qmax, was 434.78 mg g−1. Studying the thermodynamic showed that the adsorption of CR dye onto UCs was endothermic as illustrated from the positive value of enthalpy (21.37 kJ mol−1). According to the values of ΔG°, the adsorption process was spontaneous at all selected temperatures. The value of ΔS° showed an increase in randomness for the adsorption of CR dye by UCs. The value of activation energy was 18.40 kJ mol−1.

Grafting a Porous Metal–Organic Framework [NH2-MIL-101(Fe)] with AgCl Nanoparticles for the Efficient Removal of Congo Red

“…In addition, the second-order kinetics equation can provide a theoretical value of q e as 232.6 mg·g –1 and K 2 as 4 × 10 –3 (g·mg –1 ·min –1 ), while the actual adsorption capacity of q e was 234.5 mg·g –1 according to eq ; thus, the second-order kinetics was closer to the actual adsorption capacity. Furthermore, the adsorption rate of the FMA composite exhibited a more favorable adsorption rate, since the K 2 value was larger than 0.9 × 10 –5 g·mg –1 ·min –1 using a new uracil-modified chitosan adsorbent for Congo red by the four-step method …”

“…Furthermore, the adsorption rate of the FMA composite exhibited a more favorable adsorption rate, since the K 2 value was larger than 0.9 × 10 –5 g·mg –1 ·min –1 using a new uracil-modified chitosan adsorbent for Congo red by the four-step method. 29 …”

Cd2+ and Zn2+ Complexes with 2,4,6‐Tri(2‐pyridyl)‐s‐Triazine and Terephthalate for Rapid, High‐Capacity Adsorption of Congo Red

“…[ 44 , 45 ] To further explore the mechanism of CR adsorption on Cd‐MOF, we measured the kinetic data and fitted them to three kinetic models (pseudo‐first‐order, pseudo‐second‐order, and intra‐particle diffusion). [ 46 , 47 , 48 , 49 , 50 ] Figures S7a–S7c plot log(q e ‐q t ) vs. t, t/q t vs. t, and q t vs. t, respectively. The corresponding model constants were calculated according to the equations, and the R 2 value were obtained.…”

“…The adsorption rate of dye depends on the contact between adsorbent and dye molecules and the diffusion of dye molecules [44–45] . To further explore the mechanism of CR adsorption on Cd‐MOF, we measured the kinetic data and fitted them to three kinetic models (pseudo‐first‐order, pseudo‐second‐order, and intra‐particle diffusion) [46–50] . Figures S7a–S7c plot log(q e ‐q t ) vs. t, t/q t vs. t, and q t vs. t, respectively.…”

Effect of Single-Walled Carbon Nanotubes on the Adsorption of Basic Red 12 Dye by Trimellitic Anhydride Isothiocyanate-Cross Linked Chitosan Hydrogel

“…The most efficient technique used for removing the dyes is the adsorption process particularly when the adsorbents are cheap, abundant and easily obtainable [13,14]. In addition, the adsorption process is characterized by high performance, simplicity, ease of operation, high possibility for restoring and reusing of the adsorbents and its use does not result in any harmful by-products [15,16].…”