Equilibrium and Molecular Mechanism of Anionic Dyes Adsorption onto Copper(II) Complex of Dithiocarbamate-Modified Starch

Abstract

The assembly of dyes molecules on metal-polymer complexes is of interest due to their potential applications in photovoltaic cell, separation, and wastewater treatment. In the present work, the interaction of anionic dyes (acid orange 7, acid orange 10, acid green 25, and acid red 18) with the copper(II) complex of dithiocarbamate-modified starch (DTCSCu) was investigated. The sorption studies showed that the interaction mechanism was based on chelating adsorption. The equilibrium data fitted well with Langmuir-Freundlich isotherm, and the capacities followed the order AO7 > AG25 > AR18 > AO10. It was affected by the structure of the dye. The sulfonate groups located on benzene rings favored efficient adsorption. Despite the difference in capacity, the molar n(dye):n(Cu) ratios for acid orange 10, acid red 18, and acid green 25 were approximately 1:2 when the maximum capacities for the dyes were achieved at the optimal pH of 4. It suggested that one dye molecule bound to one dinuclear copper center on DTCSCu. The molar n(dye):n(Cu) ratio for the smallest dye, acid orange 7 (AO7), approached 1:1, demonstrating two AO7 molecules binding to two copper ions of the dinuclear core. The dyes adsorption related to the dinuclear copper core available on the polymer was further verified by electron spin resonance studies. Such interaction resulted in the formation of a ternary dye-metal-polymer complex. The ternary complexes were more stable than DTCSCu, which favored the adsorptions.

Behaviors and mechanism of acid dyes sorption onto diethylenetriamine-modified native and enzymatic hydrolysis starch

“…This can deduce that attachment of sulfonic acid groups on the benzene rings (AG25, AO7) with -NH 3 + of the CAES appeared to be stronger than those on the naphthalene rings (AO10, AR18) for the high intensity of negative charge distribution. This is an interesting finding, since many authors have found similar trend that anionic dyes with sulfonic acid groups on benzene rings are easily to be adsorbed than those on naphthalene rings [39,40], but have no explanation for it. It also can be seen that AG25 which contains two sulfonic acid groups on the benzene rings suffers less sorption capacity reduction (0.801 mmol L −1 ) comparing with AO7 (1.206 mmol L −1 ) with only one sulfonic acid group on its molecule, indicates that electrostatic interaction is of importance to the sorption.…”

Acid/base bifunctional carbonaceous nanomaterial with large surface area: Preparation, characterization, and adsorption properties for cationic and anionic compounds

“…To confirm these, the adsorptions of cationic compound MB and anionic compound AR18 onto pure-C, HCNP/CTS (5%), HCNP/CTS (10%), and HCNP/CTS (20%) were investigated, where cationic MB and anionic AR18 were chosen as model adsorbates because of their well-known adsorption characteristics [15,16]. Fig.…”

“…1). To examine the availability of HCNP samples acting as dual-use adsorbents that could be used not only for capturing cationic compound but also for adsorption of anionic compound, we selected methylene blue (MB) and acid red 18 (AR18) as the cationic and anionic model compounds [15,16], respectively, and thoroughly investigated the kinetics, equilibrium, and thermodynamics regarding the adsorptions of MB and AR18 on the HCNP samples (Fig. 1).…”

Fabrication of modified porous starch for the removal of vanadate from aqueous solutions

“…In our previous studies, a new kind of crosslinking starch was developed as copper, nickel and chromate fixation agents [9][10][11]. However, they could not fix the vanadium (V) effectively.…”