Adsorption of Azo-Anionic Dyes in a Solution Using Modified Coconut (Cocos nucifera) Mesocarp: Kinetic and Equilibrium Study

Abstract

The effect of adsorbent dose and initial concentration on removing the azo-anionic dyes Congo Red andtartrazine present in a synthetic aqueous solution was studied using natural cellulose (CC) and modified cationic cellulose (MCC) from coconut mesocarp. Three levels of adsorbent dosage (5, 8 and 12 mg/L) and initial concentration (40, 70 and 100 mg/L) were used. Cetyl trimethyl ammonium chloride (CTAC) was used as a modifying agent. TGA and DSC showed that the extracted cellulose was of good quality, composed mostly of cellulose with lignin and hemicellulose traces, and 8% moisture. The FTIR spectrum showed the effectiveness of the modification in the structure of the material with symmetric deformation of the C6H6-Cl group in 1472 cm−1 present in the CTAC. It was found that decreasing the adsorbent dosage and increasing the initial concentration favored the dyes’ adsorption capacity on the two bioadsorbents. Tartrazine removals of 5.67 mg/g on CC and 19.61 mg/g on MCC were achieved, and for CR of 15.52 mg/g on CC and 19.99 with MCC with removal percentages over 97% with the quaternized biomass in all cases. The kinetic and equilibrium study was carried out to identify the mechanisms involved in the adsorption process. The Freundlich model can describe the equilibrium isotherm data of tartrazine on CC and MCC. In contrast, those of CR is defined by the Langmuir and Dubinin–Radushkevic models for CC and MCC, respectively Adsorption kinetics showed that equilibrium was reached at 30 min, with rapid adsorption in the initial minutes with the removal of about 97% of the contaminant in the first 5 min; fitting to kinetic models showed that the kinetics of tartrazine on CC was fitted by Elovich (R2 = 0.756), and on MCC the Elovich (R2 = 0.887) and pseudo-second-order (R2 = 0.999) models. Removing CR on CC was fitted by pseudo-first-order, pseudo-second-order and Elovich models (R2 > 0.98), and when using MCC, all models show a good fitting with R2 = 0.99 in all cases.

Functionalized PVA film with good adsorption capacity for anionic dye

“…This result was attributed to the fact that when the initial concentration of CR increases, the driving force of the concentration gradient increases, which resulted in an increase in the diffusion processes and thus the mass transfer of dye molecules occurs from the aqueous solution to the adsorbent surface. [ 50 ] On the other hand, the R% of CR exhibited an increase from 94.6% to 96.5% with an increase in the initial CR concentration from 50 to 100 mg/L and then showed a decrease from 96.5% to 92.4% with further increases in the initial CR concentration (beyond 100 mg/L). This was because, at low CR concentration, the number of CR molecules available in the aqueous solution was less than the number of available sites on the adsorbent film.…”

Removal of Toxic Copper Ion from Aqueous Media by Adsorption on Fly Ash-Derived Zeolites: Kinetic and Equilibrium Studies

“…The adsorbent dose influences the number of active sites available for the adsorption of pollu- The influence of the adsorbent dose has a great effect on the adsorption process. The adsorbent dose influences the number of active sites available for the adsorption of pollutants [40]. The influence of the adsorbent dose on the adsorption capacity of the prepared adsorbent was investigated (Figure 4a).…”

Assessing the Plant Phytoremediation Efficacy for Azolla filiculoides in the Treatment of Textile Effluent and Redemption of Congo Red Dye onto Azolla Biomass

“…Finally, the equilibrium stage shows gradual adsorption dominated by porous diffusions. Therefore, diffusion between particles intervened in the adsorption process but cannot control the CR molecules' overall adsorption [40].…”