Biomimetic mineralization and characterization of hierarchically structured hydrated magnesium carbonates: The effects of sodium alginate

Biomimetic mineralization of hydrated magnesium carbonate for hydrogel reinforcement and heavy metal adsorption

With excessive Mn(Ⅱ) and Cu(Ⅱ) pollution in aquatic environments posing potential health risks to inhabitants, the emergence of carbon capture, utilization and storage (CCUS) technology has promoted the improvement of heavy metal remediation technologies. Using hydrothermal sediment as a crystal seed, rhamnolipid was used to mediate biomimetic mineralization to prepare hydrated magnesium carbonate (HMC) composites to enhance the Mn(Ⅱ)/Cu(Ⅱ) adsorption performance of alginate hydrogels. Hydrothermal sediment is beneficial for accelerating biomimetic mineralization, while rhamnolipid can induce a crystalline phase transformation from dypingite to nesquehonite. The addition of sediment significantly enhanced the compressive mechanical properties and thermal stability of the hydrogels. The adsorption performances of the nesquehonite and dypingite hydrogels were better for Mn(II) and Cu(II), respectively. An increase in the amount of sediment improved the adsorption of Cu(II) by the hydrogels appropriately, resulting in stronger selectivity for Cu(II). The adsorption of Mn(II) and Cu(II) on the hydrogel beads was thermodynamically spontaneous. The inhibitory effects of sodium dodecyl benzene sulfonate (SDBS), fulvic acid (FA) and alginate on Cu(II) adsorption were more obvious than those of bovine serum albumin (BSA). Both the complexation of functional groups on alginate and mineralization by HMC participated in the adsorption of Mn(II) and Cu(II).

Preparation of basic magnesium carbonate nanosheets modified pumice and its adsorption of heavy metals

Heavy metal pollution in wastewater poses a grave danger to the environment and the human body. Pumice is a mineral with abundant reserves and low prices, and its prospect of heavy metal adsorbent is very broad. In this work, we modified pumice with basic magnesium carbonate nanosheets by a convenient hydrothermal synthesis. The adsorption capacity of heavy metals is greatly improved. The effects of different pH and adsorption dosages are investigated. All the optimum pH values for Cu2+, Pb2+, and Cd2+ are 5. The adsorption of three kinds of ions conforms to the quasi-second-order adsorption kinetics model. The theoretical adsorption capacities of Cu2+, Pb2+, and Cd2+, which are calculated by the Langmuir model, are 235.29 mg/L, 595.24 mg/L, and 370.34 mg/L, respectively. The adsorption of Cu2+ and Cd2+ fit the Langmuir model better. The Freundlich model is fitted well with the adsorption of Pb2+. In the experiment simulating real wastewater, the adsorption capacity of heavy metals is not affected. It also shows good reusability in three regeneration cycles. And Mg5(CO3)4(OH)2·4H2O@pumice adsorption column showed the good removal efficiency of three heavy metals at different concentrations and different spatial velocities in the column experiment. Thus, it is believed that the Mg5(CO3)4(OH)2·4H2O@pumice is a promising adsorbent for the efficient removal of heavy metals.