Document Type: CASE STUDY


Department of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran


Bentonite bleaching earth is utilized for purifying used motor oil through a recovery process in order to improve the quality and stability of the final product. Indeed, spent bleaching earth is generated due to adsorbing oil impurities. Polluted spent bleaching earth contains 20-40% (w/w) oil and is flammable. Its disposal without pre-treatment leads to loss of oil along with environmental impacts. Accordingly, similar studies have been conducted since 1979 until now. This research was a laboratory study on reactive dye adsorption. Cleaning bleaching clay, thermal remediation and acid washing activation methods were utilized. Response surface methodology was used to design the experiments and determine the optimal parameters in order to run the dye adsorption process. The main experimental parameters have been concluded as temperature (200-800 °C), acid solution concentration (0.1-3 M), dye solution concentration (1-35 ppm), and ratio of activated earth to dye solution (0.1-2 %, w/w). Results revealed that dye adsorption process along with oil removal at a temperature of 650 °C, acid solution concentration of 0.83 M, dye solution concentration of 11.75 ppm and ratio of activated earth to dye solution of 1.52 % (w/w) results in an adsorption efficiency of 68.57%. This removal efficiency is a bit higher than activated virgin bleaching earth and much higher than virgin bleaching earth, which has adsorption capacities of 66.75% and 51.56%, respectively. Considering this recycling process, the purified material is quite acceptable technically, environmentally and economically.

Graphical Abstract


  • Dye adsorption followed by activated bleaching earth as a novel method of adsorbent SBE remediation
  • Enhancing adsorption capacity around 20% in comparison with virgin bleaching earth
  • Application of RSM acted to optimize the dye adsorption capacity
  • Thirty optimum scenarios were selected through the "design expert software" and validated by the related experiments.


Main Subjects

Alam, M., (2007). The strength of the mineral soil and the impact of acidic activation process in    removing dyes from textile wastewater. MSc. thesis in Persian, K.N.Toosi University of Technology, Tehran, Iran.

Al-Zahrani, A.A ; Daous, M.A., (2000). Recycling of spent bleaching clay and oil recovery. Process Safety Environ. Protect., 78(3): 224-228 (5 pages).       

Arulkumar, M.; Sathishkumar, P. ; Palvannan, T., (2011). Optimization of Orange G dye adsorption by activated carbon of Thespesia populnea pods using response surface methodology. J. Hazard. Mater., 186(1): 827-834 (8 pages).

Ayazi, Z.; Khoshhesab, Z.M. ; Norouzi, S., (2016). Modeling and optimizing of adsorption removal of Reactive Blue 19 on the magnetite/graphene oxide nanocomposite via response surface methodology. Desalination and Water Treatment, 57(52): 25301-25316 (16 pages).  

Bapat, S.A.; Jaspal, D.K., (2016). Parthenium hysterophorus: Novel adsorbent for the removal of heavy metals and dyes. Global J. Environ. Sci. Manage., 2(2): 135-144 (10 pages).    

El-Geundi, M.S., (1991). Colour removal from textile effluents by adsorption techniques. Water Res., 25(3): 271-273 (3 pages).

Forgacs, E., Cserhati, T.; Oros, G., (2004). Removal of synthetic dyes from wastewaters: a review. Environment international, 30(7): 953-971 (19 pages).

Gupta, V.K.; Khamparia, S.; Tyagi, I.; Jaspal, D.; Malviya, A., (2015). Decolorization of mixture of dyes: A critical review. Global J. Environ. Sci. Manage., 1(1): 71-94 (24 pages).

Hussin, F.; Aroua, M.K.; Daud, W.M.A.W., (2011). Textural characteristics, surface chemistry and activation of bleaching earth: A review. Chem. Eng. J., 170(1): 90-106 (17 pages).

Karimifard, S.; Moghaddam, M.R.A., (2016). Enhancing the adsorption performance of carbon nanotubes with a multistep functionalization method: Optimization of Reactive Blue 19 removal through response surface methodology. Process Safety Environ. Protect., 99: 20-29 (10 pages).

Khoo, L.E., Morsingh, F. and Liew, K.Y., 1979. The adsorption of β-carotene I. by bleaching earths. J. Am. Oil Chem. Soc., 56(7): 672-675 (4 pages).

Koupaie, E.H.; Moghaddam, M.A. ; Hashemi, S.H., (2012). Investigation of decolorization kinetics and biodegradation of azo dye Acid Red 18 using sequential process of anaerobic sequencing batch reactor/moving bed sequencing batch biofilm reactor. Int. Biodeterior. Biodegrad., 71:43-49 (7 pages).

Lee, C.K.; Low, K.S.; Chung, L.C., (1997). Removal of some organic dyes by hexane‐extracted spent bleaching earth. J. Chem. Tech. Biotech., 69(1): 93-99 (7 pages).

Lee, C.K.; Low, K.S.; Gan, P.Y., (1999). Removal of some organic dyes by acid-treated spent bleaching earth. Environ. Tech., 20(1): 99-104 (6 pages).

Lee, C.G.; Seng, C.E.; Liew, K.Y., (2000). Solvent efficiency for oil extraction from spent bleaching clay. J. Am. Oil Chem. Soc., 77(11): 1219-1223 (6 pages).   

Loh, S.K., Cheong, K.Y. ; Salimon, J., (2017). Surface-active physicochemical characteristics of spent bleaching earth on soil-plant interaction and water-nutrient uptake: A review. Appl. Clay Sci., 140: 59-65 (7 pages).

Low, K.S.; Lee, C.K.; Wong, A.M., (1996). Carbonized spent bleaching earth as a sorbent for some organic dyes. J. Environ. Sci. Health, Part A:, 31(3): 673-685 (13 pages).

Rafatullah, M.; Sulaiman, O.; Hashim, R.; Ahmad, A., (2010). Adsorption of methylene blue on low-cost adsorbents: a review. J. Hazard. Mater., 177(1): 70-80 (11 pages).

Radaei, E.; Moghaddam, M.R.A. ; Arami, M., (2014). Removal of reactive blue 19 from aqueous solution by pomegranate residual-based activated carbon: optimization by response surface methodology. J. Environ. Health Sci. Eng., 12(1): 65 (17 pages).

Rich, A.D., (1967). Major factors that influence bleaching performance. J. Am. Oil Chem. Soc., 44(7):  298A–323A (6 pages).

Rossi, M.; Gianazza, M.; Alamprese, C.; Stanga, F., (2003). The role of bleaching clays and synthetic silica in palm oil physical refining. Food Chem., 82(2): 291-296 (6 pages).

Sadri Moghaddam, S.; Alavi Moghaddam, M.R. ; Arami, M., (2010). A comparative study of acid red 119 dye adsorption onto dried sewage sludge and sewage sludge ash: isotherm, kinetic and desorption study. J. Residuals Sci. Tech., 7(4): 199-207 (9 pages).

Santos, S.C. ; Boaventura, R.A., (2008). Adsorption modeling of textile dyes by sepiolite. Appl. Clay Sci., 42(1): 137-145 (9 pages).    

Shahi, M., (2015). Thermal regeneration of spent bleaching earth in used oil re-refining facilities. MSc. Thesis in Persian, Civil and Environmental Engineering, K. N. Toosi University of Technology, Tehran, Iran.

Shahi, M.; Sabour, M.R.; Amiri, A.; Ghasemnezhad, M., (2015). Cleaning spent bleaching clay through using solvent extraction method and RSM statistical approach. Cumhuriyet Sci. J., 36(7): 23-40 (8 pages).

Tsai, W.T.; Chen, H.P.; Hsieh, M.F.; Sun, H.F.; Chien, S.F., (2002). Regeneration of spent bleaching earth by pyrolysis in a rotary furnace. J. Anal. Appl. Pyrolysis, 63(1): 157-170 (14 pages).

Tsai, W.T.; Chang, Y.M.; Lai, C.W.; Lo, C.C., (2005). Adsorption of basic dyes in aqueous solution by clay adsorbent from regenerated bleaching earth. Appl. Clay Sci., 29(2): 149-154 (6 pages).

Weng, C.H.; Pan, Y.F., (2007). Adsorption of a cationic dye (methylene blue) onto spent activated clay. J. Hazard. Mater., 144(1): 355-362 (8 pages).            

Woumfo, D.; Kamga, R.; Figueras, F.; Njopwouo, D., (2007). Acid activation and bleaching capacity of some Cameroonian smectite soil clays. Appl. Clay Sci., 37(1): 149-156 (8 pages).

Wu, X.; Hui, K.N.; Hui, K.S.; Lee, S.K.; Zhou, W.; Chen, R.; Hwang, D.H.; Cho, Y.R. and Son, Y.G., (2012). Adsorption of basic yellow 87 from aqueous solution onto two different mesoporous adsorbents. Chem. Eng. J., 180: 91-98 (7 pages).

Zhong, Z.Y.; Yang, Q.; Li, X.M.; Luo, K.; Liu, Y. and Zeng, G.M., (2012). Preparation of peanut hull-based activated carbon by microwave-induced phosphoric acid activation and its application in remazol brilliant blue R adsorption. Ind. Crops Prod., 37(1): 178-185 (8 pages).



Sabour, M.R.;  Shahi, M.; Dezvareh, G.A., (2017). Reactive dye extraction utilizing regenerated bleaching earth. Global J. Environ. Sci. Manage., 3(3): 299-310.

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