Effective remediation of Pb 2+ polluted environment by adsorption onto recyclable hydroxyl bearing covalent organic framework.

The removal of heavy metal ions from wastewater has attracted considerable interest because of their toxicity. Adsorption is one of the most promising methods for the removal of heavy metal ions due to its simplicity and effectiveness. Recently, covalent organic frameworks (COFs) have become promising adsorbents for effective wastewater remediation. However, many building blocks have been developed, and the design of COFs with high adsorption efficiency remains a challenge. Here, a covalent organic framework (DHTP-TPB COF) decorated with hydroxyl groups was developed for the efficient removal of Pb 2+ ions. The DHTP-TPB COF showed excellent performance in adsorbing Pb 2+ from aqueous solution. More importantly, DHTP-TPB COF exhibited high selectivity for Pb 2+ compared to other competing ions, capturing Pb 2+ ions with a removal efficiency of over 96% at pH 4. The results show that the DHTP-TPB COF exhibits excellent adsorption capacity at pH 4 of up to 154.3 mg/g for Pb 2+ ions; the value is comparable to many previously reported COFs. Moreover, the adsorbed Pb 2+ ions could be easily eluted with a 0.1 M EDTA solution, and the DHTP-TPB COF can be reused for more than five adsorption-desorption cycles without significant loss of adsorption capacity. Moreover, the adsorption mechanism was revealed using XPS analysis, indicating the formation of strong coordination-bonding interactions between hydroxyl and Pb 2+ ions. Therefore, the DHTP-TPB COF prepared herein has high potential for the treatment of Pb 2+ -contaminated wastewater and is promising for the adsorption of Pb 2+ ions in practical applications.