Performance of biochar-supported copper and cobalt on tetracycline adsorption and its application in piggery wastewater

In this study, the performance of biochar (BC)-supported cobalt (Co) and copper (Cu) (CoCu@BC) on tetracycline (TC) adsorption in aqueous solution and piggery wastewater was investigated. Scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area, Fourier-transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) were used to characterize the CoCu@BC adsorbent. The influence of initial pH, TC concentration, adsorbent dosage, and co-existing ions on TC adsorption performance was studied. Meanwhile, the adsorption kinetics, isotherm, and diffusion models were studied. The results showed that the CoCu@BC was characteristic of 142.1745 m²·g⁻¹ (BET surface area), 0.035987 cm³·g⁻¹ (microspore volume), and 3.74 (pH_PZC). The adsorption of TC on CoCu@BC well fitted with the pseudo-second-order model and the Freundlich isotherm. The maximum adsorption capacity of CoCu@BC was 621.118 mg/g, which was less influenced by pH while greatly inhibited by NO₂⁻ and SO₄²⁻. Finally, the removal of TC (94.5%), NH₄⁺-N (27%), and COD (18%) by CoCu@BC was carried out in piggery wastewater, indicating its superior performance in practice application.