Low cost and sustainable biochar-based nanocomposite for the effective remediation of persistent Alizarin Red S

Huge volumes of wastewater including dyes are occasionally released to the environment lacking any treatment or landfilled as waste that are challenging to manage and remove regardless of the treatment technique employed. Therefore, this work focused on removal of Alizarin Red S (ARS) as an anionic dye from aqueous solutions. To achieve this goal, bovine bone was employed as a source of hydroxyapatite which was modified by Fe(II) to produce a new biosorbent material with magnetic properties. Comparative studies between the hydroxyapatite (HA) and the magnetic hydroxyapatite (HA – Fe) have been executed to remove ARS dye. The Zero Point Charge (pHZPC) was estimated to be 8.4 and 10.8 for HA and HA – Fe, respectively. Hence the best pH for the sorption was desired at 5.0 which is less than pHZPC. The kinetic investigations demonstrated that the values of qt steadily reached equilibrium after 60 min to be 173 and 142.6 mg/g by HA and HA – Fe, respectively. The sorption obeys pseudo-second-order theory and the most likely nature of ARS sorption by both HA and HA – Fe is chemisorption since the effective diffusion coefficient was in the order of 10−15 m2/s. The maximum sorption capacity of ARS by HA and HA – Fe was computed from Langmuir theory to be 250 and 370.2 mg/g, respectively. Also, using the Dubinin-Radushkevich isotherm, the mean free energy was identified to be between 8 and 16 kJ/mol, this indicates that the sorption follows chemical ion exchange. Based on the thermodynamics, the sorption has endothermic nature and is spontaneous. Overall, magnetic hydroxyapatite is thought to be a good option for wastewater treatment because it is an eco-friendly material.