Efficient multi-ion adsorption using chitosan-malonic acid film: Enhancement using response surface methodology

Area of Science:

• Environmental Science
• Materials Science
• Chemistry

Background:

• Industrial wastewater often contains toxic heavy metals and metalloids like hexavalent chromium (Cr(VI)), arsenite (As(III)), and fluoride (F-).
• Conventional water treatment methods can be costly and less effective for removing these specific pollutants.
• Chitosan, a biopolymer, shows promise for adsorption but often requires modification to enhance its capacity and stability.

Purpose of the Study:

• To synthesize and characterize a novel adsorbent material based on chitosan crosslinked with malonic acid (CMA).
• To investigate the efficacy of the CMA adsorbent in removing Cr(VI), As(III), and F- ions from aqueous solutions.
• To optimize adsorption parameters and evaluate the adsorbent's performance, including capacity, kinetics, thermodynamics, and reusability.

Main Methods:

• Chitosan was crosslinked with malonic acid at a 1:0.5 mass ratio to form a film adsorbent.
• Adsorbent characterization utilized techniques such as FT-IR, TGA-DSC, SEM-EDX, XRD, and BET surface area analysis.
• Batch adsorption experiments were conducted varying pH, dosage, concentration, temperature, and time, with optimization using response surface methodology (RSM).

Main Results:

• The CMA adsorbent demonstrated over 95% removal efficiency for Cr(VI), As(III), and F- ions under optimized conditions.
• Adsorption followed pseudo-second-order kinetics and fitted the Langmuir isotherm model.
• Maximum adsorption capacities were 687.05 mg/g for Cr(VI), 26.72 mg/g for As(III), and 51.38 mg/g for F-.
• The adsorption process was spontaneous and endothermic, and the adsorbent showed good reusability over five cycles.
• The synthesis process was eco-friendly with a low E-factor of 0.0028.

Conclusions:

• Chitosan crosslinked with malonic acid (CMA) is a highly effective and sustainable adsorbent for removing Cr(VI), As(III), and F- from water.
• The optimized CMA adsorbent exhibits excellent adsorption capacities and stability, making it suitable for practical water treatment applications.
• The study highlights the potential of modified biopolymers as environmentally benign solutions for tackling complex water pollution challenges.