One-dimensional coordination supramolecular polymer [Cu(bipy)(SO4)]n as an adsorbent for adsorption and kinetic separation of anionic dyes

• The polymer showed extraordinary high adsorption capacity on all of the three dyes.
• The adsorption is based on ionic exchange.
• The kinetic studies show that the adsorption process is very fast.
• The dyes’ molecular structure affect the adsorption process significantly.
• The polymer can separate the dyes quickly and efficiently.

A coordination supramolecular polymer, [Cu(bipy)(SO4)]n, was prepared as an adsorbent. It has a molecular structure of one-dimensional chain with dense adsorption sites. Three divalent dyes including Congo red, Orange G and Reactive Brilliant red X-3B were tested as pollutants in the adsorption study. The adsorbent showed extraordinary adsorption capacity for all three dyes, reaching 2429 mg/g, 915 mg/g and 1333 mg/g for Congo red, Reactive Brilliant red X-3B and Orange G, respectively. The Langmuir isotherm model can well describe the adsorption isotherm. In kinetic study, all of the three dyes presented a model of pseudo second-order. According to the kinetic rate constants, the adsorption processes are very fast and different for three dyes. The difference can be attributed to the divalent character and the different structure of the dye’s molecule. Based on their discrepancy of adsorption velocity, separation of dyes was attempted through kinetic separation between Congo red and X-3B. A separation coefficient was developed, which can well describe the separation performance results. The results show that the two dyes can be separated quickly and efficiently by [Cu(bipy)(SO4)]n.

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