Decorated gelatin polymer onto copper aluminum layered double hydroxides for superior removal of Congo red: Optimization and adsorption evaluation of kinetics, isotherms, and thermodynamics

Azo-dyes are highly soluble in water and well documented by their toxic and nonbiodegradable characters and the removal of such dye pollutants from wastewater is aimed to control environmental pollution. Therefore, the current study is designed and executed to efficiently remove Congo Red dye pollutant (CRDP) as an example of azo-dye coloring materials by using a newly synthesized nanobiosorbent. The aimed Cu/Al-LDHs@Gltn nanobiosorbent was prepared by the direct combination and binding of gelatin as a sustainable biopolymeric material with copper aluminum layered double hydroxides (Cu/Al-LDHs) by using a green microwave synthesis approach. Several characterization techniques were applied to confirm the morphology and structure of Cu/Al-LDHs@Gltn. The particle size range was identified by using the SEM analysis from 16.54 nm to 30.68 nm and the EDX investigation confirmed the elemental existence of C (25.1%), O (41.9%), and N (13.5%), Al (3.2%), Cu (11.9%) and Cl (4.4%) elements. The FT-IR analysis referred to the incorporation of several surface functionalizations as –OH, COOH, metal-O and others, while the BET-surface area configuration was detected (41.35 m² g⁻¹). Zero-charge point of Cu/Al-LDHs@Gltn was also measured to provide (pHzpc = 6.0). The significant controlling parameters were testified to optimize the pollutant adsorption onto the aimed Cu/Al-LDHs@Gltn via batch removal experiments by using 5-15 mg/L CRDP concentrations. The optimum pH (2.0), reaction duration (35 min), dosage (15 mg) and reaction temperature (25°C) conditions were concluded. Several related models to adsorption isotherm and kinetic studies were explored. The thermodynamic parameters additionally estimated the spontaneity and the exothermal adsorptive reaction of CRDP onto Cu/Al-LDHs@Gltn. This was confirmed to afford high stability and sustainability providing successive efficiency up to 94.6%, 84.1% and 78.8% (1^st cycle) and yielded 83.3%, 70.1% and 64.5% (3^rd cycle) upon testifying 5, 10 and 15 mg/L CRDP concentrations, correspondingly. Cu/Al-LDHs@Gltn was finally characterized by excellent CRDP removal efficiency up to 92.1-95.1% (5 mg/L CRDP), 91.9-92.3% (10 mg/L CRDP) and 90.4-91.7% (15 mg/L CRDP) from drinking, sea and wastewaters, correspondingly.