Abstract
Adsorption of Alizarin Red S (ARS) on graphene oxide/poly(amidoamine) (GO/PAMAM) was studied at different ARS initial concentrations, temperatures, pHs, shaking rates and contact times. Adsorption sites of GO/PAMAM were phenolic -OHgroup of GO and amine groups (-NH2, -NH3+ and -NHR2+) of PAMAM dendrimer moieties of GO/PAMAM. At pH = 2 and 318 K, maximum adsorption capacity of the adsorbent was 1275.2 mg g-1 which is one of the highest capacity in the literature. Thus, GO/PAMAM in this work acted as a superadsorbent for ARS. At the incipient of adsorption, molecules were adsorbed on sites that was reaction-controlled step, (Ea = 114.5 kJ mol-1). Adsorption of on the remaining sites was diffusion-controlled. In alkaline media, two other types of ARS molecules were identified during that were adsorbed on and sites. Further increasing the pH of the solution, decreased the number these two sites and yielded a reduced adsorption capacity . Methylene blue (MB), thionine (Th), pyronin Y (PY), acridine orange (AO), methyl blue (MEB) and janus green (JG) dyes were selectively separated from their mixtures with ARS molecules using GO/PAMAM at pH of 2. The used adsorbent was recycled efficiently by using ethylenediamine very fast.
Highlights
Wastewater generated by different industries contains pollutant compounds that are hazardous to the health of human beings and animals
At pH = 2, the negative ΔS values observed in adsorption of Alizarin Red S (ARS)– molecules on the surface of graphene oxide (GO)/PAMAM in region I and sections IIB, showed electrostatic interaction occurred between ARS– molecules with phenolic –OH (Ph) and –NH+3 adsorption sites of GO/PAMAM
The t-plot micropore area for ARS-adsorbed GO/PAMAM at pH = 0 was 0.0075 m2 g–1 and ARS-adsorbed GO/PAMAM at pH = 2 and pristine adsorbent were lack of micropores. These results showed that as GO/PAMAM at pH = 0 adsorbed less ARS molecules than GO/PAMAM at pH = 2, the BET surface area and slit pore volume of adsorbent at pH = 0 were less than those values at pH = 2 and part of adsorbent pores at pH = 0 changed to micropores
Summary
Wastewater generated by different industries contains pollutant compounds that are hazardous to the health of human beings and animals. A number of techniques used for this purpose are filtration,[1] chemical oxidation,[2] ion exchange,[3] biological degradation,[4] reverse osmosis,[5] coagulation,[6] and adsorption.[7] Adsorption is a facile, cost effective and widely-applied method to remove dye compounds from wastewater systems and in many cases can be recycled . The adsorption process of ARS on GO/PAMAM surface was carried out under different experimental conditions including ARS concentration, ionic strength, pH, temperature, shaking rate and contact time. Due to high adsorption capacity of GO/PAMAM for ARS, GO/PAMAM was considered as a superadsorbent for ARS dye, Table 1.
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