Facile solvent-free modified biochar for removal of mixed steroid hormones and heavy metals: isotherm and kinetic studies

Abstract

Water contamination has become a global challenge to human survival. Non-biodegradable heavy metal cations and steroid hormones could accumulate in the human body and could result in serious health problems. In this study, we prepared biochar from waste shells of African star apples and modified biochar using a solvent-free ball milling facile method. The X-ray photoelectron spectrometer (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis revealed biochar functional groups in C=C, C–O, and C=O. Brunauer Emmett Teller (BET) was used to determine the surface area, the surface area of ball-milled biochar obtained at 550 °C (BASA550) increased from 174 m2/g to 304 m2/g after modification. The Langmuir and Freundlich adsorption isotherms best described the experimental adsorption data with RL < 1 and 1/n < 1 and a high degree of agreement of R2 data; Langmuir (R2 = 0.9291–0.9992) and Freundlich (R2 = 0.9077–0.9974). The adsorption kinetic studies using pseudo-first-order and pseudo-second-order models revealed that the pseudo-second-order model accurately described the adsorption process). The application of the BASA550 for treating wastewater samples showed a good percentage of removal. The removal percentage for cadmium, nickel, and lead was recorded as 92.96%, 90.89%, and 90.29%, respectively. The percentage removal in the influent and effluent were found to be 85.06%, 83.87%, 84.73%, and 89.37%, 86.48%, and 87.40%, respectively. The maximum percentage removal of steroid hormones from ultrapure water ranged from 84.20 to 89.63%, while from the spiked effluent and influent the percentage removal of 78.91–87.81% and 73.58–84.51% were obtained. The reusability of the ball-milled biochar was investigated and the result showed that the adsorbent (BASA550) had a good reusability potential for the first four cycles.Graphical