Efficient removal of herbicide 2,4-dichlorophenoxyacetic acid from aqueous solution investigated by batch, column, and membrane separation methods

Hypercrosslinking of biphenyl to form poly-biphenyl (poly-biph) with high specific surface area (SA_BET) of 1056 m² g⁻¹ by a facile microwave-assisted method was used as a potent adsorbent for removing 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solution. The poly-biph as an adsorbent has effectively removed 2,4-D by using either of the batch, column, and membrane filtration methods. In batch adsorption method, a maximum adsorption capacity of 849 mg g⁻¹ was estimated at pH of 7 within 90 min, achieving the permissible limit (<70 ppb) as per United States Environment Protection Agency (USEPA) when 4 ppm initial concentration of 2,4-D was used. The poly-biph was recyclable up to six adsorption–desorption cycles without any chemical activation. In membrane filtration method, 5 L of safe drinking water was sustained up to 150 min at a pressure of 2 bar and permeate flux of 65 L m⁻² h⁻¹, achieving a maximum removal efficiency of 98.4 %. Whereas, in a continuous fixed-bed column mode, 2.5 L of herbicide solution was treated, and permissible limit was achieved up to 40 min with a breakthrough capacity of 15 mg g⁻¹. The efficient adsorption could be achieved due to pore filling effect and π-π interactions between the adsorbent and adsorbate.