A novel 3D hierarchical NiFe-LDH/graphitic porous carbon composite as multifunctional adsorbent for efficient removal of cationic/anionic dyes and heavy metal ions

Developing effective adsorbents for wastewater purification is crucial, as excessive emissions of toxic dyes and heavy metal ions have been proven harmful to ecosystems and human health. A NiFe-layered double hydroxide/ graphitic porous carbon (NiFe-LDH/GPC) composite was fabricated by introducing NiFe-LDH nanosheets into GPC via a simple hydrothermal method to utilize the advantages of both materials fully, and thus ultimately obtain a composite adsorbent with improved adsorption properties. The samples obtained were comprehensively characterized by various characterization means, and the effects of several critical influential factors on the pollutant uptake capability of the NiFe-LDH/GPC were also studied through batch experiments. The results show that the as-synthesized NiFe-LDH/GPC exhibits a three-dimensional (3D) fluffy ultrathin-wall hierarchical porous structure, which possesses a high specific surface area and pore volume separately up to 506.74 m2/g 2 /g and 0.22 cm3 3 g- 1 as well as a relatively narrow pore size distribution. These characteristics bring advantages to enhance the adsorption ability of the NiFe-LDH/GPC for cationic/anionic dyes and heavy metal ions such as congo red (CR), malachite green (MG) and hexavalent chrome (Cr(VI), which reached the maximum adsorption capacity of 1726.51 mg/g, 1157.11 mg/g and 155.72 mg/g under the optimum conditions, respectively. Meanwhile, the adsorption behavior can be well described by the pseudo-second-order kinetic model and Langmuir isotherm model, reflecting that the sorption process mainly occurred chemically in the adsorbent monolayer. Furthermore, the NiFe-LDH/GPC maintained relatively high adsorption performance after multicycle testing, manifesting its good recyclability and stability.