Engineered clay-alginate composites for tetracycline removal: Mechanistic insights and sustainable processing

Tetracycline (TC) contamination in aquatic systems poses significant environmental risks, necessitating the development of effective remediation technologies. In this study, montmorillonite/sodium alginate (MT/SA) composite beads were developed for TC removal, achieving outstanding adsorption capacities (445-499 mg g^-1), exceeding those reported for many existing materials. XRD analysis revealed a dual adsorption mechanism: external surface binding at lower TC concentrations and interlayer adsorption at higher concentrations. FTIR analysis confirmed electrostatic interactions between TC and the composite matrix. Fixed-bed column experiments demonstrated practical applicability, treating 100 bed volumes and reducing TC concentrations to below 0.5 mg L^-1 within 150 min (Ct/C₀ = 0.1), with breakthrough curves well-fitted by the Thomas model (r² > 0.98). Ab initio molecular dynamics simulations revealed critical contributions from water "bridges," charge transfer, and hydrogen bonding. These millimeter-sized beads, produced via a simple and scalable process, offer practical advantages such as improved handling and reduced pressure drop, making them promising candidates for large-scale pharmaceutical contaminant remediation using clay-biopolymer composites.