Synthesis, Characterization and Optimization of MgNiFe-CO3 Layered Double Hydroxide Material for Textile Dye Removal

The uncontrolled discharge of synthetic azo dyes such as methyl orange (MO) into water bodies has become a major environmental concern because of their strong chemical stability, limited biodegradability, and harmful effects on aquatic ecosystems. In this study, MgNiFe layered double hydroxides (LDHs) were synthesized through a co-precipitation route using a molar ratio of (Mg + Ni)/Fe equal to 3, and their adsorption ability toward MO in aqueous media was investigated. The prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX), Fourier-transform infrared spectroscopy (FTIR), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The characterization results revealed the successful formation of a hydrotalcite-like layered structure with good crystallinity, a relatively uniform distribution of metallic species, and the incorporation of carbonate anions within the interlayer galleries. In addition, the adsorption performance was evaluated by studying the effects of several operational factors, namely adsorbent dosage, initial pH, and contact time. To better understand the interaction between these parameters and identify the optimum operating conditions, a Box–Behnken response surface design was applied. The results indicate solution pH is the most influential parameter in the adsorption process. Under optimized conditions, a maximum removal efficiency of 86.86% was obtained, corresponding to an adsorption capacity of approximately ~86.86 mg·g−1 (based on 100 mL solution volume). The enhanced adsorption performance may be attributed to the combined effect of the multivalent metal cations (Mg2+, Ni2+, and Fe3+), likely increases the surface positive charge density of the LDH and promotes interactions with anionic dye molecules. These interactions are suggested to involve electrostatic attraction and possible surface adsorption processes. However, in the absence of post-adsorption characterization, the exact adsorption mechanism remains hypothetical. Overall, the results demonstrate the promising potential of MgNiFe LDHs as efficient adsorbent materials for the treatment of dye-contaminated wastewater.