Cheap and green loofah as the substrate material was modified with epichlorohydrin and iminodiacetic acid (IDA) to obtain iminodiacetic acid-modified loofah (IDA-LG), and loaded zirconium (IV) onto IDA-LG by a simple complexation reaction to obtain novel biocomposite: zirconium-modified loofah (Zr-IDA-LG). The influence factors and adsorption mechanisms were explored by characterization and adsorption study toward catechol and amoxicillin in batch and fixed-bed modes. The study found that the surface morphology, specific surface area and internal functional groups of the adsorbent changed significantly, the isoelectric point of Zr-IDA-LG was shifted in the acidic direction (2.68 for Zr-IDA-LG) after the modification. This showed that modification of the loofah was successful. The adsorption of catechol and amoxicillin by Zr-IDA-LG showed that the pH range of the material was wide, and the coexisting ions had adverse effects on adsorption. The maximum adsorption capacity of Zr-IDA-LG from Langmuir model was 44.9±11.2 mg·g−1 for catechol and 16.8±;1.2 mg·g−1 for amoxicillin at 293 K. The adsorption isotherm and kinetic model of Zr-IDA-LG manifested that the adsorption process was dominated by monomolecular layer adsorption for catechol and monomolecular layer adsorption for amoxicillin with the presence of heterogeneous adsorption. Both adsorption processes were accompanied by ion exchange. The higher column and lower flow velocity were favorable for the fixed bed adsorption, while the Yan model could fit the fixed bed adsorption behavior. The adsorption quantity in column performance from breakthrough curves was to 20.0 mg·g−1 for catechol and 15.8 mg·g−1 for amoxicillin. Regeneration with 75% ethanol of spent Zr-IDA-LG was remarkable. The biocomposite is promising for removing some pollutants from water.