Efficient photo-degradation of antibiotics by waste eggshells derived AgBr-CaCO3 heterostructure under visible light

The semiconductors have created a great avenue in visible-light photocatalysis and recently insulator photocatalysis has become an appealing research spot. Herein, a novel waste eggshells derived AgBr-CaCO3 heterostructure was finely designed and constructed through a simple co-precipitation method for efficient antibiotics photo-degradation under visible light. The optimal heterostructure achieved a pseudo-first-order kinetic constant of 6.0 × 10-2 min−1 for tetracycline (TC) degradation, with 72 and seven-fold enhancement than eggshell (ES) and AgBr, which also exhibited superior performance towards ofloxacin and sulfamethoxazole. The density functional theory (DFT) calculations revealed that the covalent interaction of Ag-O provided a specific channel for interfacial electrons transfer from the semiconductor to the insulator and thus greatly elevated the photocatalytic activity. The highly selective ·CO3– radicals generated by ES, as the main active species, also accelerated the antibiotics degradation. Furthermore, the possible degradation pathways, aquatic toxicity and mutagenicity variation of TC were thoroughly elucidated. This current study illuminated a new pathway for the design of insulator photocatalysts based upon waste solids and demonstrated its application prospect in the field of antibiotics degradation.