Thermodynamic, isothermal, and kinetic analysis of mercury (II) adsorption on marine sediments

This study aims to investigate the potential of marine sediments as effective natural adsorbents for the removal of mercury ions (Hg (II)) from aqueous solutions. Sediment samples with total organic matter ranging from 3.7 % to 8.2 % were collected from five stations, river and sea, with different water salinities (28 to 42 g L −1 ). To explore the role of sediment′s organic matter in removal efficiency, parts of the collected sediments were subjected to hydrogen peroxide (H 2 O 2 ) oxidation. The morphology, surface area, and structure of all sediments were investigated. The effects of experimental conditions were studied. The results indicated that 0.5 g of the untreated sediment was capable of quantitatively remove Hg (II) ions up to 100 µg L −1 at the salinity of 35 g L −1 while the H 2 O 2 -treated sediments resulted in a 40 % efficiency. Moreover, the adsorption capacity of the untreated sediment was 2.5 times higher than those obtained by H 2 O 2 -treated sediments. The pseudo-second-order kinetic model successfully described the adsorption process (R 2 ≥0.9992), indicating the rapid adsorption process. The adsorption process was mainly controlled by ion-exchange interactions. These research findings may contribute to the development of new water treatment strategies, highlighting the significance of naturally available materials in addressing environmental challenges. • The efficiency of marine sediments for removal of Hg (II) ions was evaluated. • The impact of the sediment′s organic matter was studied using H 2 O 2 -treated sediments. • The untreated sediment showed 2.5 times greater adsorption capacity than treated sediments. • The kinetic, isotherm, and thermodynamic analyses were conducted on both sediments. • The adsorption kinetic was fast and mainly controlled by ion exchange interactions.