Adsorption of Congo red dye onto antimicrobial terephthaloyl thiourea cross-linked chitosan hydrogels

Abstract

Adsorption capacity of three antimicrobial terephthaloyl thiourea cross-linked chitosan hydrogels for Congo red dye removal from its aqueous solution has been investigated for the first time in this work. These hydrogels were prepared by reacting chitosan with various amounts of terephthaloyl diisothiocyanate cross-linker. The effect of the hydrogel structural variations and several dye adsorption processing parameters to achieve the best adsorption capacity were investigated. The hydrogels' structural variations were obtained by varying their terephthaloyl thiourea moieties content. The processing variables included initial concentration of the dye solution, temperature and time of exposure to the dye. The adsorption kinetics and isotherms showed that the sorption processes were better fitted by the pseudo-second-order equation and the Langmuir equation, respectively. On the basis of the Langmuir analysis Congo red dye gave the maximum sorption capacity of 44.248 mg/g. The results obtained confirmed that the sorption phenomena are most likely to be controlled by chemisorption process. The adsorption reaction was endothermic and spontaneous according to the calculated results of adsorption thermodynamics.

Improvement of dyes removal from aqueous solution by Nanosized cobalt ferrite treated with humic acid during coprecipitation

“…Kinetic experiments are the same to those of equilibrium tests but within time reached to 3 h or equilibrium. The pseudo-first-order and pseudo-second-order equations were designated by the following equations (2 and 3, respectively) [39,40]:…”

“…Four models for equilibrium adsorption isotherms were applied [40]. The models are Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R).…”

“…The Langmuir model is employed and the values of q max were determined by applying the linear form of Langmuir equation [39,40,44].…”

“…The linear form of D-R equation is given as (Eq. 8) [42,45,62]: Table 3 Adsorption isotherms parameters for adsorption of RR and MB dyes onto H6 and H8 calcined at 300 ºC a Langmuir equation C e /q e = C e /q max + 1/(K L •q max ) [35,36,40] b Freundlich equation Logq e = logK f + 1/n logC e [35,36] Samples Dye Langmuir isotherm model a Freundlich isotherm model b where q d is theoretical adsorption capacity (mg/g), R is gas constant, T is temperature, β is D-R isotherm constant, and ε = Polanyi potential. The plots of lnq e vs. ε 2 (Fig.…”

Photocatalytic Degradation of Congo Red Using PbTiO3 Nanorods Synthesized via a Sonochemical Approach

“…Besides, it is metabolized to benzidine, a known human carcinogen and there may be some allergic reactions in contact with it. The reason of chosen Congo red dye in this work because of its high solubility in water solution, complex chemical structure, and its firmness, once it is discharged into the natural environment ,. Hence, because of its malefic health effect, it is essential to remove these types of toxic dyes from the aquatic sources in an efficient and economical way …”