Zn 2+ removal from the aqueous environment using a polydopamine/hydroxyapatite/Fe 3 O 4 magnetic composite under ultrasonic waves.

In this study, an easily magnetically recoverable polydopamine (PDA)-modified hydroxyapatite (HAp)/Fe 3 O 4 magnetic composite (HAp/Fe 3 O 4 /PDA) was suitably synthesized to exploit its adsorption capacity to remove Zn 2+ from aqueous solution, and its structural properties were thoroughly examined using different analytical techniques. The effect of multiple parameters like pH, ultrasonic power, ultrasonic time, adsorbent dose, and initial Zn 2+ concentration on the adsorption efficiency was assessed using RSM-CCD. According to the acquired results, by increasing the adsorbent quantity, ultrasonic power, ultrasonic time, and pH, the Zn 2+ adsorption efficiency increased and the interaction between the variables of ultrasonic power/Zn 2+ concentration, pH/Zn 2+ concentration, pH/absorbent dose, and ultrasonic time/adsorbent dose has a vital role in the Zn 2+ adsorption. The uptake process of Zn 2+ onto PDA/HAp/Fe 3 O 4 followed Freundlich and pseudo-second order kinetic models. The maximum capacity of Zn 2+ adsorption ( q m ) obtained by PDA/HAp/Fe 3 O 4 , HAp/Fe 3 O 4 , and HAp was determined as 46.37 mg g -1 , 40.07 mg g -1 , and 37.57 mg g -1 , respectively. Due to its good performance and recoverability (ten times), the HAp/Fe 3 O 4 /PDA magnetic composite can be proposed as a good candidate to eliminate Zn 2+ ions from a water solution.