Study on the Adsorption Behavior of Tin from Waste Liquid Crystal Display Using a Novel Macroporous Silica-Based Adsorbent in One-Step Separation

Recovering indium tin oxide (ITO) is a crucial way to alleviate the indium (In) and tin (Sn) resources shortage and eliminate environmental pollution while treating the waste liquid crystal display. Since the key to ITO recovery lies in In and Sn separation, the adsorption behavior of Sn in one-step separation was studied with a macroporous silica-based adsorbent, D2EHPA/SiO 2 -P, which was successfully synthesized and well characterized. The adsorption selectivity, adsorbent dosage, adsorption kinetics, adsorption isotherms and thermodynamics, and desorption performance were analyzed to explore a new simple procedure and solve the complicated adsorption procedure D2EHPA for the tedious process of several times extraction and back-extraction. The batch experiments revealed that D2EHPA/SiO 2 -P presented significant adsorption selectivity for Sn(IV) with SF Sn/other metals over 1479 in 6 M H 2 SO 4 solution, and XPS revealed that both P=O bond and P-O bond were involved in the chemical reaction as an electron acceptor during the adsorption of Sn(IV). The adsorption equilibrium was obtained within 10 min. The adsorption process was homogeneous monolayer chemisorption and endothermic chemical process. The adsorption capacity at 298 K, 308 K, and 318 K were 52.31, 56.54, and 61.35 mg/g, respectively. The adsorption mechanism results suggested that O-H bond in D2EHPA participated in bonding and performed a substitution reaction with free Sn(IV) ions with an energy of about 0.016 eV in the adsorption process. Furthermore, O-H in NaOH played a decisive role in the desorption process, directly bonded to Sn atom, causing Sn-O bond to break with an energy of about 1.738 eV