Enhanced adsorption of Cd(II) and Pb(II) from water using edible amino acid-grafted microcrystalline cellulose

Rapid industrial development has resulted in significant heavy metal pollution in water. An effective strategy for removing heavy metals is to utilize adsorbents; however, traditional adsorption methods face challenges such as slow adsorption rates and environmental risks. In the present study, we synthesized a novel edible adsorbent derived from microcrystalline cellulose (MCC) by grafting aspartic acid (ASP) and polyaspartic acid (PASP). The findings reveal that PASP-grafted MCC (PASP-MCC) exhibited superior efficacy in removing Cd(II) and Pb(II) from aqueous solutions, significantly outperforming ASP-grafted MCC (ASP-MCC) and pristine MCC. Cd(II) and Pb(II) were rapidly adsorbed on the amino acid-grafted MCC, and the process is best described by the pseudo-first-order model. According to the Langmuir model, the maximum adsorption capacities of PASP-MCC for Cd(II) and Pb(II) were 36.5 mg/g and 57.56 mg/g, respectively, representing 12.6-fold and 9.5-fold increase compared to pristine MCC. The adsorption mechanism of the amino acid-grafted MCC primarily involves complexation and physisorption. Safety and efficacy evaluation revealed that PASP-MCC significantly reduced the toxicity and accumulation of Cd(II) and Pb(II) in medaka fish. These important findings suggest that amino acid-grafted cellulose, particularly PASP-MCC, could serve as an effective edible heavy metal absorbent in aquaculture water and drinking water in the future.