Transformation of Mytella falcata residual shell into CaAl/LDH adsorbent: Removal of methyl orange and methylene blue dyes

Abstract This study analyzed the viability of using malacoculture residue ( Mytella falcata ) to produce layered double hydroxides (LDHs) and for its subsequent use as an adsorbent. The CaAl/LDH‐RE material was produced with calcium oxide from the residue and the CaAl/LDH‐AP was produced with a commercial reagent. Both were used to remove methyl orange (MO) and methylene blue (MB) dyes. The CaAl/LDH‐RE presented a surface area of 28.54 m 2 g −1 , being 65.62% larger than the CaAl/LDH‐AP material (17.23 m 2 g −1 ). The adsorbents showed mesopores distributed on a surface formed by plates in the form of hexagonal sheets arranged in an overlapping manner. The dosage of 0.05 g L −1 obtained the removal of 95% and 97% for MO, while for MB it was 94% and 93% using the adsorbents LDH/CaAl‐AP and LDH/CaAl‐RE, respectively. The system reached equilibrium at 90 min for MO and 120 min for MB. The pseudo‐second order model well represented the kinetic data reaching 11.36 mg g −1 (CaAl/LDH‐RE) and 8.42 mg g −1 (CaAl/LDH‐AP) for MO, and 4.47 mg g −1 (CaAl/LDH‐RE) and 4.14 mg g −1 (CaAl/LDH‐AP) for MB. The Freundlich model better represented the isothermal data, where the temperature exerted little influence. Adsorbents showed similar removal percentages in real and synthetic matrices. The LDH/CaAl‐RE can be applied in up to 3 cycles, maintaining its adsorption capacity. These results corroborate the use of MFW to produce CaAl/LDH‐RE, which can be used for the efficient removal of organic pollutants in an aqueous solution.