RESUMEN
Developing effective water treatment materials, particularly through proven adsorption methods, is crucial for removing heavy metal contaminants. This study synthesizes a cost-effective three-dimensional material encapsulating graphitic carbon nitride-layered double oxide (GCN-LDO) in sodium alginate (SA) through the freeze-drying method. The material is applied to remove uranium (U(VI)) and cadmium (Cd(II)) in real water systems. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analyses conclusively verified the elemental composition and successful encapsulation of GCN-LDO within the SA matrix. Removal effectiveness was tested under various conditions, including adsorbent dose, ionic strength, contact time, temperature, different initial pollutant concentrations, and the impact of co-existing ions. The adsorption of U(VI) and Cd(II) conformed to the pseudo-second-order (PSO) kinetic model, signifying a chemical interaction between the sodium alginate-graphitic carbon nitride-layered double oxide (SA-GCN-LDO) sponge and the metal ions. The Langmuir isotherm indicated monolayer, homogeneous adsorption for U(VI) and Cd(II) with capacities of 158.25 and 165.00 mg/g. SA-GCN-LDO recyclability was found in up to seven adsorption cycles with a removal efficacy of 70%. The temperature effect study depicts the exothermic nature of the U(VI) and Cd(II) ion removal process. Various mechanisms involved in U(VI) and Cd(II) removal were proposed. Further, continuous fixed bed column studies were performed, and Thomas and the Yoon-Nelson model were studied. These insights from this investigation contribute to advancing our knowledge of the material's performance within the context of U(VI) and Cd(II) adsorption, paving the way for optimized and sustainable water treatment solutions.
RESUMEN
Waste marble powder (WMP) is a rich source of calcium and magnesium salts having an affinity for fluoride ions and therefore serves as a good defluoridation agent. Hydroxyapatite was synthesized from WMP generated by the marble processing industry to make an adsorbent for drinking water defluoridation. The synthesized marble hydroxyapatite (MA-Hap LR) powder was further formed into 2-3 mm pellets by extrusion spheronization technique using a polyvinyl alcohol binder. Continuous column defluoridation studies were conducted to obtain optimized column parameters such as input fluoride concentration, column inflow rates, optimum pellet size, and adsorbent bed parameters to obtain maximum fluoride adsorption capacity. The best breakthrough column performance was a maximum adsorption capacity of 1.21 mg/g, treating 10 mg/L fluoride concentration. The optimized column flow rate was at 1 LPH using an adsorbent bed height of 25 cm, which processed 28.5-bed volumes at an adsorbent exhaustion rate of 7.4 g/L. The column breakthrough performance data were fit into various kinetic models (Thomas model and Yoon-Nelson model) to describe adsorption kinetics and obtain correlation coefficients. Thomas's model fitted well with a high correlation coefficient value. Modelling studies indicate MA-Hap as a promising adsorbent for drinking water treatment, and optimum column design parameters were identified for scale-up for real applications.
