Simultaneous adsorption of cationic and anionic dyes using a novel multifunctional mesoporous silica

Amir Vahid,Majid Abdouss,Shahnaz Nayeri,Aliakbar Miran Beigi

doi:10.24200/amecj.v4.i01.127

Abstract

In the present work a multifunctional nanoadsorbent was synthesized via a well-designed stepwise route, led to the grafting of an amine group on the interior and acidic sites on the exterior of bimodal mesoporous silica nanoparticles (UVM-7). First, amine and thiol groups were grafted on the interior and exterior pores of silica through co-condensation and post synthesis treatment, respectively. Then, the oxidation of thiol on UVM-7 caused to create sulfonic acid and the subsequent template extraction was carried out to obtain the NH2/UVM-7/SO3H. The results of XRD, the nitrogen sorption, SEM, TEM, FT-IR and elemental analysis revealed the presence of both types of functional groups on UVM-7. Then, simultaneous adsorption of anionic and cationic dyes (Methylene Blue [MB] and Direct Red 23 [Dr]) using NH2/UVM-7/SO3H was investigated. UV-Vis spectrophotometry was utilized for the determination of dyes in single and binary solutions. Langmuir and Freundlich models were used for the fitting of obtained experimental adsorption data and the constants of both isotherms were calculated for MB and Dr. Morover, the calculation of thermodynamic parameters revealed that the adsorption of MB and Dr on NH2/UVM-7/SO3H was endothermic and spontaneous.

Highlights

Dyes as a important raw material were used in different industries including cloth, plastics, tanning, cosmetics and food [1]
By approaching to the saturated relative pressure, increasing of gas uptake led to the sharp increasing of isotherm. This can be attributed to the inter particles of UVM type material which is present in NH2/UVM-7/ SO3H after internal and external grafting of organic moieties
In all cases including single and binary solutions, the pseudosecond order model has better coefficient of determination, R2, which means that kinetic of adsorption od Methylene Blue (MB) and Direct red (Dr) on NH2 /UVM-7/SO3H can be explained by The difference between two kinetic model can be attributed to the number and accessibility of adsorption sites, specific surface area, pore size, nature of the functional groups of adsorbent and chemical structure of dyes

Summary

Introduction

Dyes as a important raw material were used in different industries including cloth, plastics, tanning, cosmetics and food [1]. CTAB of the assynthesized NH2/UVM-7/SO3H was removed by reflux in 1 molar ethanolic solution of HCL for 24 hours to get access to the internal pores and amine groups. These results proof presence of amine and sulfonic acid functional groups on NH2/UVM-7/SO3H.

Results

Conclusion