Synthesis and adsorption application of amine shield-introduced-released porous chitosan hydrogel beads for removal of acid orange 7 from aqueous solutions

Abstract

An effective and low-cost adsorbent named amine shield-introduced-released porous chitosan hydrogel beads (APCB) was synthesized and characterized by SEM, EDX, FTIR, XPS and the zeta potential. SEM images showed the porous structure of APCB and EDX analysis proved the adsorption behavior of Acid Orange 7 (AO7) onto APCB. FTIR analysis indicated that the amine-shield-release process and amine-introduce process both increased the amount of amine groups. XPS analysis confirmed the chemical compositions of the APCB. Zeta potential analysis indicated that the pH_pzc of APCB was 5.4. The significance of this work was illustrated by the excellent adsorption capacity towards AO7. The maximum adsorption was observed at pH 2.0 with the adsorption capacity of 2803.77 mg g⁻¹. APCB showed low adsorption capacity in high pH values and exhibited better AO7 adsorption capacity in low ionic strength solutions. Experimental data were well fitted by a pseudo-second-order kinetic model and Langmuir isotherm model. Thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic.