The remediation potential and kinetics of Pb²⁺ adsorbed by the organic frameworks of Cladophora rupestris

Cladophora rupestris is ubiquitous in many kinds of waterbodies, and C. rupestris biomass can serve as a carrier for adsorbing and transferring heavy metals. Batch experiments and characterization were performed. Results showed that the organic frameworks of C. rupestris (CROF) had a specific surface area of 2.58 m²/g and an external surface area of 2.06 m²/g. Many mesopores were present in CROF, mainly distributed in 2.5-7.5 nm. The zeta potentials were within the range of - 4.46 to - 13.98 mV in the tested pH of 2.0-9.0. CROF could effectively adsorb Pb²⁺ in large pH range. The maximum adsorption capacity (q_max) of Pb²⁺ on CROF was 15.02 mg/g, and 97% of Pb²⁺ was adsorbed onto CROF after 25 min. CROF had a preferential adsorption of Pb²⁺. The protein secondary structures and carbon skeletons of CROF all worked in adsorption. The main Pb²⁺ adsorption mechanisms were pore filling, electrostatic attraction, Pb-π interaction, and surface complexation. Therefore, it is valuable as a biosorbent for the removal of Pb²⁺ from waterbodies.