Characteristics and mechanisms of cadmium adsorption onto biogenic aragonite shells-derived biosorbent: Batch and column studies

Abstract

Calcium carbonate (CaCO 3)-enriched biomaterial derived from freshwater mussel shells (FMS) was used as a non-porous biosorbent to explore the characteristics and mechanisms of cadmium adsorption in aqueous solution. The adsorption mechanism was proposed by comparing the FMS properties before and after adsorption alongside various adsorption studies. The FMS biosorbent was characterized using nitrogen adsorption/desorption isotherm, X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, Fourier-transform infrared spectroscopy, and point of zero charge. The results of batch experiments indicated that FMS possessed an excellent affinity to Cd(II) ions within solutions pH higher than 4.0. An increase in ionic strength resulted in a significant decrease in the amount of Cd(II) adsorbed onto FMS. Kinetic study demonstrated that the adsorption process quickly reached equilibrium at approximately 60 min. The FMS biosorbent exhibited the Langmuir maximum adsorption capacity as follows: 18.2 mg/g at 10 °C < 26.0 mg/g at 30 °C < 28.6 mg/g at 50 °C. The Cd(II) adsorption process was irreversible, spontaneous (−∆G°), endothermic (+∆H°), and more random (+∆S°). Selective order (mmol/g) of metal cations followed as Pb 2+ > Cd 2+ > Cu 2+ > Cr 3+ > Zn 2+. For column experiments, the highest Thomas adsorption capacity (7.86 mg/g) was achieved at a flow rate (9 mL/min), initial Cd(II) concentration (10 mg/L), and bed height (5 cm). The Cd(II) removal by FMS was regarded as non-activated chemisorption that occurred very rapidly (even at a low temperature) with a low magnitude of activation energy. Primary adsorption mechanism was surface precipitation. Cadmium precipitated in the primary (Cd,Ca)CO 3 form with a calcite-type structure on the FMS surface. A crust of rhombohedral crystals on the substrate was observed by SEM. Freshwater mussel shells have the potential as a renewable adsorbent to remove cadmium from water.

Adsorption of Chromium(VI) onto Freshwater Snail Shell-Derived Biosorbent from Aqueous Solutions: Equilibrium, Kinetics, and Thermodynamics

“…e rod-shaped FSS particles had many crystalline microlayers and their thickness and width, respectively, were 1.5 μm and 2.8 μm. is result agreed with several previous reports by Van et al [21] with S BET of 1.45 m 2 /g for a CaCO 3 -rich biosorbent-biogenic aragonite shells-and 2.09 m 2 /g for golden apple snail shells [22]. In addition, the characteristic peaks of calcium silicate (Ca 2 SiO 4 ) were also observed with low intensity on the XRD pattern, indicating the small amount of this compound present in FSS.…”

“…us, these biomaterials are used to develop CaCO 3 -rich materials for preparing low-cost adsorbents. For instance, Flores-Cano et al [19] developed an eggshell-derived biosorbent for Cd adsorption; El Haddad [20] used a calcined mussel shell (62.24% CaCO 3 )-derived biosorbent to remove Basic Fuchsin dye; Van et al [21] developed a green biosorbent derived from freshwater mussel shells (contain >90% CaCO 3 ) for the removal of Cd with an adsorption capacity of 26.6 mg/g.…”

Sorption of Cd2+ and Pb2+ on Aragonite Synthesized from Eggshell

“…Different adsorbents such as waste adsorbents are becoming popular for waste management and creating a sustainable world. The most commonly used waste adsorbents are waste bivalve shells [27,28]. Currently, waste eggshell is also well used for the treatment of wastewater [6,17,29,30].…”

Synthesis optimisation and characterisation of chitosan-calcite adsorbent from fishery-food waste for phosphorus removal

“…The normalised XRPD patterns show the presence of both an amorphous phase, which is associated with the organic component of the material, e.g. chitin/chitosan polymer and a crystalline phase, which was identified as calcite (Swanson et al 1953;Zhou et al 2016;Cai et al 2019). The broad diffraction peaks observed at around 9.6°and 19°in the raw material (representing the amorphous chitin structure) are found to sharpen after activation, suggesting the material has crystallised during the activation process (Arulvel et al 2017).…”

“…Hence, increasing IR made the deacetylation process more efficient, aiding enhanced development of chitosan on both the exterior and interior surface of the CCM (Chu 2002). KOH also increases the pH pzc at which the surface of the adsorbent is electroneutral (pH pzc = 8.78), and it has been reported that the pH pzc of similar calcium-chitin-based adsorbents are in the range of 9-11.4 (Tap Van et al 2018). Theoretically, below this value, the surface of the material in solution is positively charged.…”