Engineered Superabsorbent Nanocomposite Reinforced with Cellulose Nanocrystals for Remediation of Basic Dyes: Isotherm, Kinetic, and Thermodynamic Studies.

Arej S Al-Gorair,Ghada A Mahmoud,Asmaa Sayed

doi:10.3390/polym14030567

Abstract

In this study, cellulose nanocrystals (CNCs) were produced from pea peels by acid hydrolysis to be used with pectin and acrylic acid (AAc) to form Pectin-PAAc/CNC nanocomposite by γ-irradiation. The structure, morphology, and properties of the nanocomposite were investigated using Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) techniques. The nanocomposite hydrogel was used for the removal of methylene blue dye (MB) from wastewater. The results revealed that the presence of CNCs in the polymeric matrix enhances the swelling and adsorption properties of Pectin-PAAc/CNC. The optimum adsorbate concentration is 70 mg/L. The kinetic experimental data were fit by pseudo-first-order (PFO), pseudo-second-order (PSO), and Avrami (Avr) kinetic models. It was found that the kinetic models fit the adsorption of MB well where the correlation coefficients of all kinetic models are higher than 0.97. The Avr kinetic model has the lowest ∆qe (normalized standard deviation) value, making it the most suitable one for describing the adsorption kinetics. The adsorption isotherm of MB by Pectin-PAAc follows the Brouers–Sotolongo model while that by Pectin-PAAc/CNC follows the Langmuir isotherm model. The negative values of ∆G confirmed the spontaneous nature of adsorption, and the positive value of ∆H indicated the endothermic nature of the adsorption.

Highlights

The results indicated that the adsorption process of methylene blue (MB) onto the nanocomposite hydrogel possesses an endothermic nature
CNCs were successfully produced from pea peels by acid hydrolysis, with an average particle size of 23.05 nm, and a zeta potential of –30.7 mV
CNCs were used in the formation of a Pectin-PAAc/CNC nanocomposite by γ-irradiation

Summary

Introduction

The dye molecules are stable and challenging to biodegrade under normal conditions, and they are toxic, carcinogenic, and allergenic to the human body [2]. Cationic (basic) and anionic (acidic) dyes are the most commonly used dyes in the textile industry because of their excellent water solubility and relatively low cost [4,5]. Methylene blue (MB) is the most common. It is used for many purposes, such as printing, paper coloring, wool dyeing, cotton dyeing, tannin dyeing, as a temporary hair colorant, and as an indicator in the oxidation-reduction process [7]. Adsorption provides excellent results because it is economical, effortless to produce, inconsiderate to toxic substances, and efficient for different dyes categories [10]

Methods

Results

Conclusion