Efficient lead removal from aqueous solutions using a new sulfonated covalent organic framework: Synthesis, characterization, and adsorption performance

Abstract

The aim of removing Pb(II) from water is to minimize the potential harm posed by toxic metals to both human health and the environment. To achieve this, a covalent organic framework adsorbent called TFPOTDB-SO3H was developed using a condensation process involving 2,5-diaminobenzenesulfonic acid and 2,4,6-tris-(4-formylphenoxy)-1,3,5-triazine. This adsorbent exhibited excellent properties such as high repeatability, selectivity, and easy solid–liquid separation. Under conditions of pH = 6.0 and 298 K, the TFPOTDB-SO3H demonstrated impressive capability of adsorbing Pb(II). In a brief span of 10 min, it attained a special elimination rate of 99.40 % and shown its capacity to adsorb up to 500.00 mg/g. The adsorbent presented effective removal of Pb(II) from a solution that had a mixture of various ions, showcasing its proficiency in capturing the contaminant, with a partition coefficient (Kd) of 3.99 × 106 mL/g and an adsorption efficiency of 99.75 % among six coexisting ions. The pseudo-second-order kinetic model was observed to govern the adsorption process kinetics, while the Langmuir isotherm model confirmed monolayer chemisorption as the mechanism for Pb(II) removal. Thermodynamic analysis indicated that the uptake process was both exothermic and spontaneous. Furthermore, the adsorbent maintained a significant adsorption efficiency of 89.63 % for Pb(II) even after undergoing four consecutive adsorption–desorption cycles. These findings collectively suggest that TFPOTDB-SO3H has excellent potential for effectively adsorbing and removing Pb(II) heavy metal ions from wastewater.

Keywords

• Covalent organic frameworks
• Adsorption
• Pb(II)
• Removal
• Aqueous solutions