Unveiling the adsorption dynamics of proteins on saponite clay nanosheets

• This work explores the use of saponite clay nanosheets for protein adsorption. • Saponite nanosheets shows a high maximum adsorption capacity of 998.8 mg·g –1 for ovalbumin. • The adsorption mechanism involves electrostatic attraction and hydrogen bonding. • The adsorption kinetics analysis reveals chemisorption as the rate-limiting step. • Saponite clay shows good adsorption efficiency of >85 % for SARS-CoV-2 spike protein. This work investigates the potential of saponite clay for protein adsorption, using ovalbumin as a model protein. The saponite sample exhibits uniform sheet-like morphology and a negatively charged surface across the tested pH range of 1–7. pH-dependent experiments reveal that optimal ovalbumin adsorption occurs at pH 3, with a high maximum adsorption capacity of 998.8 mg·g –1 . This adsorption is primarily driven by electrostatic interactions between the positively charged ovalbumin and the negatively charged saponite, as well as the hydrogen bonding between the amine groups of ovalbumin and the oxygen atoms of saponite. The adsorption isotherm follows the Langmuir model, indicating monolayer adsorption. The maximum adsorption capacity calculated using this model (1005.2 mg·g –1 ) closely aligns with the experimentally determined value (998.8 mg·g –1 ). Kinetics studies show that the adsorption of ovalbumin by saponite reaches saturation within 50 min and follows a pseudo-second-order model, suggesting that chemisorption is the rate limiting step. Additionally, saponite clay demonstrates preliminary potential for the adsorption of the SARS-CoV-2 spike protein, achieving an efficiency greater than 85 % at an optimal pH of 5. These findings highlight the considerable potential of saponite clay for protein adsorption and offer valuable insights into its protein-binding mechanisms.