Treating wastewater with elevated ammonia nitrogen levels in garbage treatment plants is a global concern, with blow-off recognized as an efficient process for nitrogen removal. However, this method generates low-concentration ammonia, presenting a challenge for adequate recovery. This study addresses this issue by impregnating metal halides onto K2CO3-activated biogas residue to create composite materials tailored for adsorbing low-concentration ammonia. We systematically investigated the impact of activation parameters, metal halide type, loading capacity, and environmental conditions on the adsorption properties of the materials. Notably, at an activation temperature of 700 °C, utilizing copper chloride with a loading capacity of 30 %, the material exhibited a saturation adsorption capacity of 29.32 mg/g for 200 ppm NH3, with a breakthrough time of 45.6 min, significantly surpassing the untreated sample and demonstrated excellent regeneration performance. SEM, BET, and FTIR analyses revealed that the material provided dispersion sites for metal halides, promoted the complexation of metal halides and ammonia and retained pores for ammonia diffusion, thereby enhancing adsorption efficiency. This innovative approach contributes to waste utilization and ensures efficient ammonia recovery through metal halide-ammonia complexation.