Fabrication of a novel chitosan/polyaspartic acid composite: A pH-tunable sorbent for efficient adsorption of heavy metal ions and dyes from water

Abstract

Heavy metal ions and dyes pollutants have caused significant environmental pollution, posing a threat to human life and ecosystems. Herein, a novel pH-tunable composite adsorbent CS-PA integrated chitosan (CS) with polyaspartic acid (PA) was fabricated. The morphology and structure of CS-PA were characterized. The results indicated that PA was successfully introduced into CS, and the particle size of CS-PA was irregular and porous with a pore diameter of 10–100 μm. Adsorption experiments demonstrated that CS-PA was efficient in removing various charge properties of heavy metal ions and dyes: cationic [Cu(II) and methylene blue (MB)], anionic [Cr(VI) and congo red (CR)] species. Also, the sorption process in the experimental conditions fitted pseudo-second-order kinetic model and Langmuir isotherm. The maximum adsorption capacity of Cu(II), MB, Cr(VI), and CR were 133.33, 172.41, 138.89, and 178.57 mg/g, respectively, based on the Langmuir isotherm study. CS-PA has strong selective sorption ability for MB over Cu(II) under the acidic condition and CR over Cr(VI) at a weakly alkaline solution in their binary systems. Multiple attractions occurred in adsorbing Cu(II), MB, Cr(VI), and CR because of their diverse charge properties and structural characteristics. Finally, regeneration studies further demonstrate that <5 % in sorption efficiency on CS-PA after 5 cycles. Thus, this composite adsorbent is tunable, versatile and potentially applicable to wastewater treatment.