Copolymerization of catechol and polyethyleneimine onto activated carbon for efficient removal of Congo red dye

Abstract

In this work, a new AC@Catechol/PEI adsorbent was prepared via the copolymerization of catechol and polyethyleneimine (PEI) onto pretreated commercial activated carbon (AC). It achieved a high adsorption capacity of 411.52 mg/g for the anionic dye Congo red (CR), which was approximately 7 times that of pretreated AC without modification. In bath adsorption experiment, 1 g of adsorbent was used to treat 4 L of 100 mg/L CR solution, resulting in 98.5% CR removal. In addition, the prepared AC@Catechol/PEI adsorbent exhibited highly efficient CR competitive adsorption against SO 4 2À ions and cationic malachite green dye. The adsorption mechanism was mainly attributed to electrostatic interactions, hydrogen bonding, and π-π stacking. Catecholamine modification greatly improved the adsorption capacity and adsorption selectivity of commercial AC for CR dyes. This low-cost adsorbent may have broad prospects for the removal of anionic dyes in wastewater.

One-Step Synthesis of Polyethyleneimine-Grafted Styrene-Maleic Anhydride Copolymer Adsorbents for Effective Adsorption of Anionic Dyes

“…Comparing the R 2 values of the Langmuir model (0.999) and the Freundlich model (0.754) in Table 2, it is evident that the adsorption process of PEI-SMA on RB5 is suited to be described by the Langmuir isotherm model, suggesting that the adsorption process involves single-molecular layer adsorption on the PEI-SMA surface. The R L = 0.00044 (0 < R L <1) indicates that the adsorption process of RB5 onto PEI-SMA is favorable [39]. The experimental data (1749.19 mg g −1 ) of PEI-SMA-adsorbed RB5 are similar to the maximum adsorption capacity computed by the Langmuir isotherm model (1809.30 mg g −1 ).…”

“…Compared with Figure 9c, after the adsorption of RB5 molecules, the peaks corresponding to -C=O-NH-and -NH2/-NHgroups in PEI-SMA shift toward higher binding energy, moving to 401.05 eV and 399.36 eV, respectively. This reveals the formation of hydrogen bonding [39]. After adsorption of RB5, the proportion of -NH2/-NHgroups on PEI-SMA significantly decreased, and new -NH3 + /-NH2 + -groups appeared, indicating an electrostatic interaction between PEI-SMA and RB5 molecules [35].…”

“…In addition, the non-linear relationship between the initial pH values and the final values are also observed in Figure 3c. When the pH value is below/above 6.21, the initial pH values are lower/higher than the pH value after adsorption, which results from the protonation/deprotonation of amine groups [39]. At pH < 3.75, RB5 (pK a = 3.75) exists in its protonated and ionized form, and PEI-SMA possesses a higher RB5 adsorption capacity due to the strong electrostatic attraction between the fully ionized -SO 3 − group of RB5 and the protonated -NH 3 + group of PEI-SMA.…”

Amine-functionalized MOF-derived carbon materials for efficient removal of Congo red dye from aqueous solutions: simulation and adsorption studies

“… 53 The calculated R L was close to 0 (0 < R L < 1), indicating that the adsorption process of CR on PEI@MDC was favorable and irreversible to a certain extent. 54 In addition, with the increase of temperature, the K L and K F values gradually increased, indicating that the adsorption was a heat-absorbing reaction, and high temperature is favorable for the reaction ( Table 4 ). In Table 5 , the maximum adsorption capacities of CR on different solid adsorbents were summarised.…”