Green synthesized hydroxyapatite nanoadsorbent for the adsorptive removal of AB113 dye for environmental applications

The present work reports the synthesis of hydroxyapatite (HAp) via the green chemistry approach by using the leaf extract of copper pod tree and its adsorptive potential to remove Acid blue 113 (AB113) dye. FESEM-EDS characterization of the synthesized HAp confirmed rod-shaped HAp with prominent Ca and P elements. The crystallinity of HAp was ascertained by XRD and thermal stability was analyzed by TGA. The colloidal suspension stability was determined as - 17.7 mV by Zeta potential analyzer. The mesoporous structure was affirmed via BET studies with a high magnitude of specific surface area. TEM studies substantiated the rod-shaped HAp as observed in FESEM. The signals specific to HAp were observed in XPS studies. Adsorption of AB113 on the synthesized HAp was examined by varying the process parameters. Batch experiments resulted in an optimum dye removal of 92.72% at a pH of 8, 1 g/L of CP-HAp nps dosage, 20 ppm AB113 concentration, 120 min contact time, 150 rpm agitation speed and at room temperature. The maximum adsorption capacity reached 120.48 mg/ g. Multifarious isotherms characterized the adsorption with Freundlich isotherm (R2 > 0.968) dominating Langmuir indicating multilayer adsorption. The experimental data reasonably matched pseudo-second-order kinetics with R2 exceeding 0.99. Thermodynamic investigations underlined the spontaneity and exothermicity of the processes. Results showed the suitability of the HAp nanoadsorbent to remove AB113 from wastestreams.

Automated summary

This study successfully synthesized hydroxyapatite (HAp) using the green chemistry approach and the leaf extract of copper pod tree, and investigated its adsorption potential for Acid blue 113 (AB113) dye. The synthesized HAp exhibited rod-shaped morphology with prominent Ca and P elements. It had high crystallinity and thermal stability. The HAp suspension showed good stability with a Zeta potential of -17.7 mV. BET studies confirmed the mesoporous structure and a high specific surface area. The HAp's ability to adsorb AB113 was examined under various process parameters. Batch experiments revealed that optimal dye removal (92.72%) was achieved at pH 8, with a dosage of 1 g/L CP-HAp nps, 20 ppm AB113 concentration, 120 min contact time, 150 rpm agitation speed, and room temperature. The maximum adsorption capacity was determined as 120.48 mg/g. Different isotherms and kinetics were used to describe the adsorption behavior, with the Freundlich isotherm and pseudo-second-order kinetics showing good fitting. Thermodynamic investigations indicated that the adsorption process was spontaneous and exothermic. Overall, this study highlights the suitability of HAp nanoadsorbent for the removal of AB113 dye from wastestreams.