Adsorption and catalytic degradation of tetracycline by modified biochar in water : A review

Tetracycline (TC) is one of the most frequently detected antibiotic contaminants in aquatic environments and poses increasing risks to ecosystems and human health. Modified biochar (modified-BC) has attracted increasing attention for TC removal, as it can act as both an efficient adsorbent and a catalyst. This review summarizes recent progress in the adsorption and degradation of TC by modified-BC, focusing on its physicochemical properties, surface functional groups, charge-transfer capability, and catalytic performance. Different modification strategies, including metal doping, non-metalic heteroatom doping, acid/alkali activation, and composite construction, are critically compared in terms of their effects on TC removal. Current studies indicate that metal-doped modified-BC generally shows more stable and superior performance than single physical or acid–base modification because it provides more active sites, improved electron transfer, and stronger catalytic reactivity. Instead of regarding adsorption–degradation synergy as a newly discovered phenomenon, this review critically summarizes how adsorption and degradation are coupled in modified–BC systems for TC removal. Particular attention is given to the quantitative distinction between adsorption-dominated removal and catalytic degradation-dominated removal, because high apparent TC removal does not necessarily indicate complete degradation. Compared with previous reviews that mainly summarized adsorption or degradation separately, this review focuses on the interfacial roles of adsorption pre–concentration, active–site exposure, electron–transfer regulation, and reactive-species generation in modified–BC systems. In addition, the practical challenges of modified-BCs, including regeneration, environmental safety, catalyst stability, and large-scale application potential, are discussed. This review provides useful guidance for the rational design and practical application of modified-BC in antibiotic-contaminated wastewater treatment.