Study on the adsorption behavior of tin from waste liquid crystal display using a novel macroporous silica-based adsorbent in one-step separation

• Separation of indium and tin was vital for recycling indium while treating waste LCD. • D2EHPA/SiO 2 -P exhibited excellent adsorption selectivity and kinetics towards Sn(IV). • Distribution coefficient SF Sn/other metals was over 1479 mL/g in 6 M H 2 SO 4 solution. • H atom in D2EHPA was exchanged by Sn atom with 0.016 eV in the adsorption process. • O H bond in NaOH caused Sn O bond to break with 1.738 eV in the desorption process. Recovering indium tin oxide (ITO) is crucial to alleviate the In and Sn resources shortage and eliminate environmental pollution while treating waste liquid crystal displays. 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 prepared and well characterized. Based on the analysis of adsorption selectivity, adsorbent dosage, adsorption kinetics, adsorption isotherms, as well as thermodynamics and desorption performance, a new simple process was explored to solve the tedious process of several times extraction and back-extraction of D2EHPA. The batch experiments revealed that D2EHPA/SiO 2 -P presented significant adsorption selectivity for Sn(IV) with SF Sn/other metals over 1479 mL/g in 6 M H 2 SO 4 solution, and XPS showed 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 mechanism indicated that the 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 the Sn atom, causing the Sn O bond to break with an energy of about 1.738 eV.