Layered double-oxide/biochar composites (ZnAl-LDO@BB) were successfully prepared by a hydrothermal method and are used to adsorb different pollutants. High-resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy were used to characterize the ZnAl-LDO@BB. The synthesized ZnAl-LDO@BB were regular microspheres, and ZnAl nanosheets were regularly embedded on the surface of the banana biochar. The adsorption properties of ZnAl-LDO@BB for four adsorbates in aqueous solution were evaluated by batch adsorption experiments. The results showed that ZnAl-LDO@BB can quickly and effectively adsorb Congo red (CR), methyl orange (MO), total phosphorus (TP), and hexavalent chromium [Cr(VI)]. Adsorption conformed to the Langmuir model and pseudo-second-order (PSO) kinetic equation, and the adsorbed amounts of CR, MO, TP, and Cr(VI) calculated by the Langmuir model were 344.83, 588.24, 322.58, and 64.52 mg/g, respectively. The mechanism of the adsorbate removal by ZnAl-LDO@BB involves surface functional group complexation, pore adsorption, and interlayer channel adsorption. Based on these results, ZnAl-LDO@BB is a multifunctional green material for water treatment and has good application prospects.