Adsorptions of Astrazon Dye onto Granular Carbon-Silica Aerogels Synthesized from Recycle Palm-Date Pits: Kinetics, Thermodynamic and Isotherm Studies

Prof Dr Ahmed Zaky Sayed

doi:10.24297/jac.v12i10.5251

Abstract

In this work, an environmental friendly management process was achieved to solve solid and liquid hazardous contaminants in our environment. In this case, a granular carbon (gAC) sorbent impregnated with SiO2 aerogels as composite (gAC/SiO2) was synthesized from the rceycling of palm-date pits solid waste products to remediate wastewater solution contaminated with Astrazon pink FG cationic dye. The Astrazon dye adsorption onto the gAC/SiO2 was investigated by compared to gAC sorbent alone using a batch system with respect to initial dye concentration, pH, contact time, solution temperature and adsorbents dosage. It was found the amount of adsorbed dye was strongly depended on pH with low significant important of temperatures levels range from 298 to 318 K. The prepared gAC/SiO2 aerogels composite exhibits high efficiency for Astrazon dye adsorption by approximately 1.5 times than that of gAC alone. The equilibrium adsorption states could be achieved in 6 h when using gAC/SiO2 comparable to 12 h by gAC for the different initial dye concentrations. The adsorption kinetics were found to best described by the pseudo-second order model (PSOM) and pseudo-first order (PFOM) kinetic models respectively, when using gAC and gAC/SiO2 sorbents, and poorest-fit with Elvoich equation as confirmed by nonlinear chi-square error test and determination coefficient values. The equilibrium isotherm study indicated that dye adsorption data were analyzed and fitted well by the nonlinear expressions of both Langmuir and Langmuir-Freundlich models compared to Freundlich, Temkin and Redlich–Petersonmodels. The maximum monolayer Astrazon dye adsorption was estimated to be 185.59 and 256.02 µmol/g by gAC and gAC/SiO2 adsorbents. The positive values of the enthalpy (ΔH°) and negative Gibbs free energy (ΔG°) changes indicate an endothermic as well as feasible and spontaneous nature of the adsorption process respectively.

Highlights

Water pollution is identified as one of the major concern because of its threats to many forms of life
The adsorption results by each adsorbent were found to be highly influenced by contact time, the pH solution, and initial dye concentrations, temperature showed a low significant effect on the dye adsorption capacity
The maximum uptake of the Astrazon dye by the prepared granular carbon (gAC) and gAC/SiO2 was attained at pH 5-7, adsorbent dose of 1 g/l, and a temperature of 318 K and adsorption capacities increased with increasing initial dye concentrations up to 400 μmol

Summary

Introduction

Water pollution is identified as one of the major concern because of its threats to many forms of life. Colored wastewater arises as a direct result of the production of organic dyes and as a consequence of its use in different industries such as leather, textile, plastics, paper, etc. Due to the good solubility of the synthetic dyes, organic dyes are common water pollutants, even in trace quantities, and they are considered to be the most recalcitrant identified wastewater pollutants to biodegradation by native microbial habitants [2,3]. Recalcitrant, and even potentially toxic, their discharge into the water environment poses serious environmental, aesthetical and health problems [1,4,5]. From an environmental and health point of view, the treatment of aqueous effluents containing soluble organic dyes is of great significance followed by secure disposal. Many techniques have been explored, such as chemical precipitation and oxidation, ion exchange, biological treatment, coagulation, reverse osmosis, photocatalytic degradation, ozonation and solvent extraction and adsorption, to remove the dyestuffs contaminants in the wastewater effluents [2,3,4,6]

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