Biochar from oil cakes: an efficient and economical adsorbent for the removal of acid dyes from wool dye house effluent

In the reported study, biochars were prepared from almond, coconut, and mustard oil cakes by chemical activation with phosphoric acid followed by low-temperature pyrolysis. The ball milling technique was employed to reduce the particle size of the biochars below 300 nm. The synthesized biochars were characterized by various analytical techniques like Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, X-ray diffraction spectroscopy, BET surface analysis, porosity measurement, methylene blue value and further employed for the removal of color from the acid dye effluent from the wool dyeing unit. The results showed that very small quantities (2.0 %) of biochars are sufficient to remove around 92% color from the dye effluent. The adsorption properties of the synthesized biochars were found to be greatly depending on the type of oil cake used. Among the three selected oil cakes, viz. mustard, coconut, and almond, the later was found to be performed well in terms of color removal. The batch adsorption and kinetic studies indicate the second order pathway of color removal for the synthesized biochars.