Cd2+ and Zn2+ Complexes with 2,4,6‐Tri(2‐pyridyl)‐s‐Triazine and Terephthalate for Rapid, High‐Capacity Adsorption of Congo Red

Abstract

Abstract Three crystal complexes were designed and synthesised through the solvothermal method, with Cu2+, Zn2+, and Cd2+ ions as the metal centres and 2,4,6‐tri(2‐pyridyl)‐s‐triazine (TPTZ) and terephthalate (BDC2−) as the ligands. Their compositions were determined to be Cd(TPTZ)Cl2 (Cd‐MOF), {[Zn(TPTZ)(BDC)] ⋅ 3H2O}n (Zn‐MOF), and Cu2(PCA)2(BDC)(H2O)2 (Cu‐MOF) (PCA−=2‐pyridinium amide), respectively. Cd‐MOF can adsorb 90 % of Congo red (CR) in 10 s at room temperature and atmospheric pressure, and CR removal was complete at 20 s over a wide pH range. The adsorption capacity for CR reached 1440 mg g−1 in 5 min. Selective adsorption was demonstrated in mixed dyes. The adsorption kinetic data agree well with the pseudo‐second‐order kinetic model. The Temkin model was successfully used to evaluate the adsorption isotherms of CR on Cd‐MOF at room temperature, suggesting that adsorption occurs through a hybrid of monolayer and multilayer mechanisms.

Keywords

• adsorbent
• Congo red
• Cu2+, Zn2+, and Cd2+ complexes
• terephthalic acid
• 2,4,6-tri(pyridin-2-yl)-1,3,5- triazine