Use of covalent organic framework TpPa(OH)2 as pH-responsive adsorbent for copper ions from water

摘要

? 2023 Elsevier B.V.For the first time, this study applied the covalent organic framework TpPa(OH)2 as a pH-responsive adsorbent for copper ions from water. The Langmuir adsorption capacities at pH 7 and 25, 35, and 45 °C are 56.2, 84.8, and 109.9 mg copper ions/g, respectively, an endothermic and entropy-driven process. The adsorption capacity of TpPa(OH)2 on copper ions at pH ?0.2 and 35 °C is reduced to 11.3 mg/g, an 86.7 loss. The layered structures of TpPa(OH)2 are deteriorated by proton attacks at pH ?0.2. The pH-swing (7, ?0.2, then 7) increases the Langmuir capacity at pH 7 by 35.5, contributed by excess sites of the exfoliated layers. The TpPa(OH)2 can be applied as a pH-responsive adsorbent, adsorbing 109.5 ± 3.2 mg copper ions/g at pH 7 and releasing 82.6 adsorbed copper ions at pH ?0.2.