Chitosan (CS) is a biopolymer that is well known for its ubiquity, biodegradability, lack of toxicity, low cost, antibacterial activity, and excellent heavy metal adsorption ability. We synthesized CS and CS@TiO2 composites (CST) with different concentrations of glutaraldehyde (crosslinking agent) solution by a simple method involving a crosslinking process (using glutaraldehyde as the crosslinking agent), a freeze-drying technique, and exchange with ammonia solution. The interaction mechanisms of the as-synthesized samples were systematically characterized by scanning electron microscopy, electron dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and the Brunauer-Emmett-Teller method. Among the as-synthesized samples, 3%CS-V (CS composites synthesized using 3% glutaraldehyde for crosslinking and exchanged with ammonia solution) at an initial concentration of 300 ppm exhibited a preferable adsorption capacity for copper ions (Cu2+), with a maximum adsorption capacity of 31 mg g− 1. Sorption equilibrium isotherms fit the Freundlich model. Compared to CS, 7%CST-V (CST composite synthesized using 7% glutaraldehyde for crosslinking and exchanged with ammonia solution) exhibited higher antibacterial activity against Staphylococcus epidermidis due to a synergistic effect. The antimicrobial efficacy against Escherichia coli was more affected by copper ions than TiO2 addition and glutaraldehyde concentration, whereas the antimicrobial efficacy against S. epidermidis was more affected by TiO2 addition and exchange with ammonia solution.