Shape-memory cellulose nanofiber/polyglutamic acid-based aerogels as novel adsorbents for the removal of heavy metals from aqueous solutions

Water bodies contaminated by heavy metals pose a severe threat to human health and the eco-system. The synthesis of eco-friendly adsorbents is essential to eliminate the use of toxic chemicals to eradicate heavy metal pollution from water bodies. In this study, a novel aerogel was prepared using a simple one-pot reaction between cellulose nanofibers and polyglutamic acid through a crosslinking reaction for the removal of lead, zinc, and copper ions from aqueous solutions. Surface analysis revealed that the aerogel consisted of abundant carboxyl and amino functional groups. The optimal pH of the solution for the adsorption of lead, zinc, and copper was 4, 5, and 5 respectively. The experimental data revealed that the adsorption followed pseudo-second-order kinetics at 22 °C for all the heavy metals. The adsorption behaviour of zinc and copper could be described through the Langmuir isotherm model whereas, the adsorption behaviour of lead was described by the Freundlich isotherm model. The maximum experimental adsorption capacity was 101.81, 59.26, 100.59 mg/g for lead, zinc, and copper respectively. The adsorption mechanisms involved were coordination bonding and electrostatic attraction. The high adsorption capacity, ease of separability and good mechanical strength deems these aerogels suitable for the adsorption of heavy metals from water.