investigation of hexavalent chromium removal from aqueous solution using granular and powdered activated carbon produced from peganum harmala seed

background and objectives: because of toxical and hazardous properties of hexavalent chromium (cr(vi)), its removal by an economical and efficient method is necessary. the use of activated carbon, as an adsorbent, is a common and effective method for hexavalent chromium removal. thus the aim of this study was to produce granular and powdered activated carbon form peganum harmala and compare their chromium removal efficiency from synthetic wastewater. materials and methods: this experimental study was carried out in a batch reactor in the laboratory. peganum harmala was used as an activated carbon production precursor and ultrasonic waves were used for carbon activation, and brunauer–emmett–teller (bet) test was used for determination of specific surface area of activated carbon.. in this study the effect of ph, adsorbent dosage, initial chromium concentration, contact time,and mixing speed were investigated. the colorimetric method using uv/vis spectrometer t80+ at a wavelength of 540 nm was used for chromium determination. data analysis was performed by excel software. results: the bet test showed that the granular and powdered activated carbon specific surface area were equal to 442 and 310 m2/g, respectively that indicates the activation process efficacy. the adsorption experiments showed that the optimum ph for cr(vi) was equal to 2 for both adsorbents and powdered activated carbon had more removal efficiency than its granular form. the kinetic tesults of the reactions indicated that both adsorbents followed pseudo-second order kinetic in the absorbtion process. conclusion: comparing specific surface area and chromium adsorption capacity shows that powdered activated carbon is a more efficient and economical adsorbent than the granular form. key words: activated carbon, adsorption, chromium (vi), peganum harmala seed, ultrasonic funding: this study was funded by birjand university of medical sciences. conflict of interest: none declared. the ethical approval: the ethic committee of birjand university of medical sciences approved the study. how to cite this article:. entezari a, khosravi r, arghavan f. a, taghizadeh a.a, khodadadi m, eslami h. investigation of hexavalent chromium removal from aqueous solution using granular and powdered activated carbon produced from peganum harmala seed. j rafsanjan univ med sci 2016; 15(7): 645-56. [farsi]