REMOVAL OF CIBACRON BRILLIANT YELLOW 3G-P DYE FROM AQUEOUS SOLUTIONS BY BRAZILIAN PEATS AS BIOSORBENTS

<div><p>Two Brazilian peat samples in different stages of decomposition, fibrous peat (FP) and decomposed peat (DP), were used as biosorbents for the removal of the textile dye Cibacron Brilliant Yellow 3G-P (CBY) from aqueous solutions. These biosorbents were characterized by Fourier transform-infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The effects of initial pH of dye solution and contact time between the dye and the biosorbents on the biosorption capacities were studied. Based on an error function (<i>F_error</i>) the general-order kinetic model provided the best fit to the experimental data compared with the pseudo-first-order and pseudo-second-order kinetic biosorption models. The equilibrium data were fitted to Langmuir, Freundlich, and Liu isotherm models. For both biosorbents the equilibrium data were best fitted to the Liu isotherm model. Simulated dye house effluents were used to check the applicability of the proposed biosorbents for effluent treatment.</p> </div

Adsorption of Alizarin Red S Dye by Carbon Nanotubes: An Experimental and Theoretical Investigation

This study evaluated the feasibility of removing Alizarin Red S dye (ARS) from aqueous solutions, using nanoadsorbents such as single and multiwalled carbon nanotubes (SWCNT and MWCNT, respectively). The effect of pH, shaking time, and temperature on adsorption was studied. The pH 2.0 was observed to show optimum removal for both of the carbon nanotubes. The equilibrium time (298–318 K) was fixed at 65 and 100 min for SWCNT and MWCNT, respectively. The kinetics of adsorption was calculated using pseudo-first-order, pseudo-second-order, and general-order equations. The calculations revealed that the general-order kinetic equation best-fit the adsorption data. The Liu isotherm model best fit the equilibrium data (298–318 K). The maximum sorption capacity at 318 K for ARS dye was 312.5 and 135.2 mg g^–1 for SWCNT and MWCNT, respectively. Change in entropy (Δ<i><i>S</i>°</i>), Gibb’s free energy change (Δ<i><i>G</i>°</i>), and enthalpy (Δ<i><i>H</i>°</i>) were calculated for the adsorption of ARS dye. The electrostatic interaction between nanoadsorbent–adsorbate was conveyed using the magnitude of change in enthalpy. Ab initio simulation was used to study the interaction of ARS with (5,5) and (8,0) SWCNTs, and (16,0) and (25,0) SWCNTs with and without vacancy. The theoretical calculations showed that the binding energies between ARS dye and SWCNTs are enhanced as the nanotube diameter gets bigger; however, the distance of binding remains unchanged. Therefore, the results from first principle calculations indicated that electrostatic interaction may be responsible for the adsorption of ARS dye onto SWCNT. The theoretical outcomes were found to be in coordination with the experimental estimates