Abstract
In the present study, pectin-alginate-titania (PAT) composites were synthesized and the adsorptive removal behavior of methylene blue (MB) from aqueous solution, as a model of synthetic organic effluents, onto the prepared PAT composites were investigated by monitoring the effect of contact time, initial MB concentration, and temperature. The adsorption isotherm data were fitted well with the Freundlich isotherm model, suggesting the surface heterogeneity of the PAT composites and that the MB adsorption occurred on the active sites on multilayer surface of the composites. The adsorption kinetics of MB was demonstrated to be pseudo-second order, governed by two intraparticle diffusion rates, and the adsorption process was exothermic, spontaneous, and more disorder. The Langmuir isotherm model suggested that the maximum adsorption capacity of MB on the PAT composites was in the range of 435–637 mg g–1. In general, it increased with the TiO2 NPs content in the PAT composites, due most likely to the increase in surface area exposing more functional groups of the pectin and alginate to interact with the synthetic dye. The adsorptive removal of MB by the PAT composites was found to be more efficient compared with many other reported adsorbents, such as graphene oxide hybrids, pectin microspheres, magnetite-silica-pectin composites, clay-based materials, chemically treated minerals, and agricultural waste. The present study therefore demonstrated for the first time that PAT composites are not only promising to be utilized as an adsorbent in wastewater treatment, but also provide an insight into the adsorption mechanism of the synthetic dyes onto the biopolymers-titania composites.Graphic abstractInsight into the adsorption kinetics, mechanism, and thermodynamics of methylene blue from aqueous solution onto pectin-alginate-titania composite microparticles.
Highlights
Synthetic dyes are cost-effective and applicable for multiple purposes, they have been utilized on a massive scale in textile, pulp, paper, pharmaceutical, and tannery industries [1]
Upon comparing the Fourier transform infrared (FTIR) spectrum of PAT(0) with those of pectin and alginate, it is clearly observed that the FTIR spectrum of PAT(0) resembles the sum of the spectra of pectin and alginate [40]
Similar spectral feature was observed in the FTIR spectra of PAT(0.005), PAT(0.05), and PAT(0.25), the intensity of broad band at 600 cm−1 originated from the TiO2 NPs increases continuously with their incorporation into the composites
Summary
Synthetic dyes are cost-effective and applicable for multiple purposes, they have been utilized on a massive scale in textile, pulp, paper, pharmaceutical, and tannery industries [1]. Since most of the synthetic dyes, detergents, catalytic chemicals, and stabilizing agents are toxic, carcinogenic, mutagenic, or teratogenic to various living microorganisms, the industrial wastewater containing even low concentrations of dyes are dangerous to aquatic life in water systems [2,3,4,5]. The objective is to explore the effect of incorporation of TiO2 NPs into the crosslinked pectin-alginate matrix, aiming on the efficient PAT composite as a promising adsorbent for the removal of the synthetic dye from wastewater. To this purpose, the PAT composites with different loading contents of TiO2 NPs were prepared using the precipitation method, and they were characterized using spectroscopic and imaging methods. The adsorption behavior, e.g. adsorption capacity, mechanism, kinetics, isotherm, and thermodynamics of MB onto the PAT composites with different TiO2 NPs loading contents were evaluated and established
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