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Health concerns have been raised over the excessive occurrences of antibiotics such as tetracycline in aquatic environments. Adsorption is a simple and cheap technique for the removal of pharmaceuticals from industrial wastewater. To date, limited information exists on the fate, economical treatment and safe disposal of spent adsorbents in the environment, and this is often considered as the main drawback of adsorption. In this article, an alternative strategy to dispose and reuse spent inorganic adsorbents is proposed. We synthesized CoO/CuFe2O4 mixed metal oxide from layered double hydroxides by a modified co-precipitation and calcination method at 500 °C for 5 h. CoO/CuFe2O4 has a 348.5 m2/g surface area, pH point zero charge of 5.8 and an average pore diameter of 5.8 nm. Results show that the tetracycline removal efficiency at pH 6 reached 96.6% and 84-87.3% in the absence and in the presence of 4 g/L competing ions (Cl− and NO3−), respectively. Moreover, CoO/CuFe2O4 retained stable activities, of about 90%, over five consecutive recycling runs. Spent CoO/CuFe2O4 was reused as a catalyst in the presence of sunlight for degradation of azo dye, and this is the first report of achieving ~ 77% discolouration of eriochrome black T dye using a recycled adsorbent. [ABSTRACT FROM AUTHOR]

• Cost-competitive hybrid (MnFe-LDO–biochar) photocatalyst was successfully prepared. • MnFe-LDO–biochar has a bandgap of 2.85 eV and a high photocurrent response of 3.8 μA. • Large surface area containing mixed metal oxide oxidizing sites of MnFe-LDO–biochar improved its antibiotic degradation. • 50 mg MnFe-LDO–biochar/K 2 S 2 O 8 degraded ∼98 % tetracycline within 60 min upon exposure to a UV light. • MnFe-LDO–biochar performed sufficiently in a wide practical pH without significant leaching. A high-efficiency layered double oxide-biochar hybrid (MnFe-LDO–biochar) catalyst was successfully synthesized by the co-precipitation-calcination process and used to effectively remove tetracycline (TC) pollution. The characterization results verified that MnFe-LDO–biochar possesses a specific surface area of 524.8 m2 g−1, appropriate bandgap (2.85 eV), a high photocurrent response (3.8 μA cm–2), a saturation magnetization of 28.5 emu g−1 and a mixture of interconnected pores. 40 % of TC was removed after 30 min when 50 mL TC solution (20 mg L−1) was treated with 50 mg MnFe-LDO–biochar in the dark and reached ∼98 % degradation rate within 240 min upon exposure to a UV light. Notably, in the presence of H 2 O 2 or K 2 S 2 O 8 , the degradation rate of MnFe-LDO–biochar was shortened to 60 min with an average pseudo-first-order rate constant of 0.0445 min−1. The antibiotic removal rate of the cost-competitive MnFe-LDO–biochar surpassed several reported materials and maintained ∼80 % reuse efficiency after 3rd successive cycles. The TC photodegradation mechanism is multiprocess induced majorly by OH and SO 4 − while h+ and O 2 − contributed partly to the mineralization. This work highlights the powerful synergistic combination of layered double oxide (LDO) and biochar. [ABSTRACT FROM AUTHOR]