Adsorption removal of Congo red onto L-cysteine/rGO/PANI nanocomposite: equilibrium, kinetics and thermodynamic studies

Abstract

In this paper, adsorption of Congo red (CR) onto L-cysteine decorated with reduced graphene oxide/polyaniline composite at room temperature was investigated. The morphology and structure properties of as-prepared nanocomposite were verified by UV-visible spectroscopy (UV-visible), powder X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FTIR), scanning electron microscopy (SEM), and Brunauer Emmett Teller (BET) studies. Effect ofabsorbent dosage, contact time, initial dye concentration and temperature were studied and optimal conditions for the adsorption process of Congo red dye were found. The obtained results indicated that isotherms data fitted well to Langmuir model. While kinetics data fitted well to the pseudo-second-order kinetic equation and the adsorption process was generally governed via intra-particle diffusion. Thermodynamic data showed that adsorption process of CR was endothermic and spontaneous in nature. At optimal conditions, the maximum adsorption capacity of CR was calculated and found to be 56.57 mg/g, which shows that L-cysteine functionalized reduced graphene oxide/polyaniline based nanocomposite can be efficiently used for wastewater management.

Multifunctional Ternary NLP/ZnO@l-cysteine-grafted-PANI Bionanocomposites for the Selective Removal of Anionic and Cationic Dyes from Synthetic and Real Water Samples

“…Pseudo-second-order rate constant K 2 , q e , and correlation coefficient ( R 2 ) were calculated from the slope and intercept of the plot (Figure a,b). R 2 for both dyes in Table gave a value of 0.999, showing excellent linearity, which suggests that the adsorption of MO and BG can be illustrated by the PSO kinetic model …”

“…In addition, in Figure a,b,d, small peaks are observed in the region between 650 and 500 cm –1 , which are assigned to the metal–oxygen vibration (Zn – O) of ZnO NPs . In Figure c, the peak of the NZC- g -PANI bionanocomposite at 3440 cm –1 is associated with O–H stretching and confirms the presence of l -cysteine . The short band at 674 cm –1 represents the C–S linkage of the cysteine group to the PANI of NZC- g -PANI (Figure b), while this band is found absent in the case of the unmodified nanocomposite, i.e., NZ-PANI (without l -cysteine).…”

“…Further increase in NZC- g -PANI dose resulted in no additional increase in BG and MO adsorption, as shown in Figure . At high dosages of the adsorbent, dye molecules are comparatively fewer in numbers to combine with all of the adsorption sites present on the NZC- g -PANI adsorbent, which gets exhausted, resulting in the reduction of adsorbent per unit mass adsorption capacity . Adsorption tends to reach an equilibrium when the adsorption mass reaches a particular value.…”

“…36 In Figure 1c, the peak of the NZC-g-PANI bionanocomposite at 3440 cm −1 is associated with O−H stretching and confirms the presence of Lcysteine. 37 The short band at 674 cm −1 represents the C−S linkage of the cysteine group to the PANI of NZC-g-PANI (Figure 1b), 38 while this band is found absent in the case of the unmodified nanocomposite, i.e., NZ-PANI (without Lcysteine). The various bands of PANI shown in Figure 1b, which appeared at 852, 1173.2, 1280, 1381, and 1680 cm −1 , are attributed to NH and CH stretching vibrations, benzenoid ring, and NH 2 bending modes.…”

Recent Advances in the Removal of Organic Dyes from Aqueous Media with Conducting Polymers, Polyaniline and Polypyrrole, and Their Composites

“…A separate class of adsorbents is represented by the polyaniline-coated carbonaceous materials, e.g., activated carbon [ 7 , 64 ]; activated carbonized peanut shells [ 65 ]; activated carbons based on prickly pear seeds [ 66 ]; carbonized tea waste [ 67 ]; graphene [ 47 , 68 ]; multiwall carbon nanotubes [ 8 ] or reduced graphene oxide [ 30 , 69 , 70 ]. Only exceptionally, polyaniline was decorated in a reverse manner by an inorganic component, such as copper(II) oxide [ 71 ].…”