Abstract
In this work, congo red (CR) was removed by applying carbonate intercalated Mg-Al-layered double hydroxide (Mg-Al-LDH) nanocompound as an adsorbent. Batch adsorption experiments performed under various temperatures, ionic strengths, initial CR concentrations, alkalinities and shaking rates. The maximum adsorption capacities of Mg-Al-LDH for CR were 100, 105 and 86.8 mg g-1 at 308, 318 and 328 K, respectively. Adsorption sites of Mg-Al-LDH for CR were -OH groups attached to Al atoms of adsorbent layers. Adsorption isotherms of the process were studied by the ARIAN model and analysis of obtained data showed that there were two kinds of adsorption sites on the surface of Mg-Al-LDH. Results of instrumental analysis showed that these adsorption sites were -OH groups located on the surface of mesopores and micropores of adsorbent and were named MP and 003 sites, respectively. The kinetic data were studied by the KASRA model and ISO and intraparticle diffusion (pore-diffusion) equations which showed that CR molecules were adsorbed at first on the MP sites. Also, during the adsorption of CR on MP sites the interaction of CR with adsorbent surface was rate-controlling step. Furthermore, during CR adsorption on 003 sites, adsorption kinetics was diffusion-controlled.
Highlights
Discharge of wastewater produced by industries is a main source of water pollution
The results showed that atomic percentages of magnesium and aluminum on its surface were 18.88 and 6.62% respectively which validated the Mg-Al-Layered double hydroxides (LDHs) formation, Fig. 4
Mg-Al-LDH nanocompound was used as the adsorbent for congo red (CR) molecules
Summary
Discharge of wastewater produced by industries is a main source of water pollution. These pollutants of the discharged wastewater are harmful to environment and human and animal health. Dye substances are one detrimental group of these pollutant compounds.[1] Large amounts of effluents containing dye compounds are generated by industries that produce paper,[2] textiles,[3] rubber,[4] food,[5] cosmetics[6] and leather.[7] Various chemical, physical and biological methods are used to remove pollutants from wastewaters Some of these methods are biological degradation,[8] coagulation/flocculation,[9] membrane separation,[10] chemical oxidation,[11] ion exchange[12] and adsorption.[13] Among these methods, adsorption is a suitable candidate for dye removal due to its simplicity, high adsorption capacity and non-toxicity. These models made possible surveying adsorption isotherms and kinetic curves
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