Tailored glutamine modified zinc-terephthalic acid/xanthan gum composite for improved removal of lead ions.

Abstract

Novel zinc-terephthalate/xanthan gum/glutamine (Zn-BDC/X/G) adsorbent was fabricated using ferric ions crosslinking gelation method for effective adsorption of Pb²⁺ from wastewater. The structure of Zn-BDC/X/G was confirmed using several characterization techniques. Zn-BDC/X/G reveals thermal permanence, advanced textural properties, pH_PZC at pH 6.8, and 97 nm as TEM particle size. The maximum adsorption capacity of Zn-BDC/X/G was 271.40 mg/g at 25 °C, pH 5, equilibrium time within 60 min, and dosage 1.5 g/L as calculated from the nonlinear Langmuir model. Nonlinear kinetic and isothermal models have accurately described the adsorption process. The impact of ionic strength in Pb²⁺ adsorption onto Zn-BDC/X/G at pH 5 appears to be a decrease of removal % by 19 when compared with 1.5 mol/L of KCl. Thermodynamic analysis for Pb²⁺ adsorption onto Zn-BDC/X/G was endothermic, high randomness at solid-liquid boundary, and spontaneous physisorption process. The best eluent for removing Pb²⁺ from the surface of Zn-BDC/X/G is HNO₃, which provides the highest desorption efficiency percent (99%). Zn-BDC/X/G composite could be reusable with a slight decrease in the removal efficiency by only 3% after eight application cycles. The above results show that Zn-BDC/X/G bio-nanocomposite is a promising, sustainable, and eco-friendly material.