Research Article
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Year 2020, Volume: 2 Issue: 1, 7 - 14, 23.06.2020

Abstract

References

  • [1] J. Wang, D. Zhang, S. Liu, C. Wang, Enhanced removal of chromium(III) for aqueous solution by EDTA modified attapulgite: Adsorption performance and mechanism, Sci Total Environ, 720, 2020, 137391.
  • [2] M. Kazemi, M. Jahanshahi, M. Peyravi, Hexavalent chromium removal by multilayer membrane assisted by photocatalytic couple nanoparticle from both permeate and retentate, J Hazard Mater, 344, 2018, 12-22.
  • [3] Z. Zhao, H. An, J. Lin, M. Feng, V. Murugadoss, T. Ding, H. Liu, Q. Shao, X. Mai, N. Wang, Progress on the photocatalytic reduction removal of chromium contamination, Chem Rec, 19, 2019, 873-882.
  • [4] L. Liu, X. Liu, D. Wang, H. Lin, L. Huang, Removal and reduction of Cr(VI) in simulated wastewater using magnetic biochar prepared by co-pyrolysis of nano-zero-valent iron and sewage sludge, J Clean Prod, 257, 2020,120562.
  • [5] C. Mangwandi, T.A. Kurniawan, A.B. Albadarin, Comparative biosorption of chromium (VI) using chemically modified date pits (CM-DP) and olive stone (CM-OS): Kinetics, isotherms and influence of co-existing ions, Chem Eng Res Des, 156, 2020, 251–262.
  • [6] L. Qin, L. He, W. Yang, A. Lin, Preparation of a novel iron-based biochar composite for removal of hexavalent chromium in water, Environ Sci Pollut Res, 27, 2020, 9214–9226.
  • [7] WHO, 2006, Guidelines for Drinking-Water Quality, 3rd edn, World Health Organization, Geneva, pp. 54.
  • [8] M. Mohsen-Nia, P. Montazeri, H. Modarress, Removal of Cu2+ and Ni2+ from wastewater with a chelating agent and reverse osmosis processes, Desalination, 217, 2007, 276-281.
  • [9] K.Y. Chen, Y.M. Tzou, Y.T. Chan, J.J. Wu, H.Y. Teah, Y.T. Liu, Removal and simultaneous reduction of Cr(VI) by organo-Fe(III) composites produced during coprecipitation and coagulation processes, J Hazard Mater, 376, 2019, 12-20.
  • [10] R. Hans, G. Senanayake, L.C.S. Dharmasiri, J.A.P. Mathes, D.J. Kim, A preliminary batch study of sorption kinetics of Cr(VI) ions from aqueous solutions by a magnetic ion exchange (MIEX) resin and determination of film/pore diffusivity, Hydrometallurgy, 164, 2016, 208–218.
  • [11] M.R. Abukhadra, A. Adlii, B.M. Bakry, Green fabrication of bentonite/chitosan@cobalt oxide composite (BE/CH@Co) of enhanced adsorption and advanced oxidation removal of Congo red dye and Cr (VI) from water, Int J Biol Macromol, 126, 2019, 402-413.
  • [12] D. Ozdes, A. Gundogdu, B. Kemer, C. Duran, M. Kucuk, Assessment of kinetics, thermodynamics and equilibrium parameters of Cr(VI) biosorption onto Pinus brutia Ten, Can J Chem Eng, 92, 2014, 139-147.
  • [13] D. Ozdes, C. Duran, Equilibrium, Kinetics, and Thermodynamic Evaluation of Mercury (II) Removal from Aqueous Solutions by Moss (Homalothecium sericeum) Biomass, Environ Prog Sustain, 34, 2015, 1620-1628.
  • [14] F. Gode, E.D. Atalay, E. Pehlivan, Removal of Cr(VI) from aqueous solutions using modified red pine sawdust, J Hazard Mater, 152, 2008, 1201–1207.
  • [15] R.R. Karri, J.N. Sahu, B.C. Meikap, Improving efficacy of Cr(VI) adsorption process on sustainable adsorbent derived from waste biomass (sugarcane bagasse) with help of ant colony optimization, Ind Crops Prod, 143, 2020, 111927.
  • [16] Y. He, S. Han, H. Lin, Y. Dong, Microwave-Assisted Modification of Corncob with Trimethylammonium Chloride for Efficient Removal of Cr(VI): Preparation, Characterization, and Mechanism, Water Air Soil Pollut, 2020, 231:137.
  • [17] S. Sugashini, K.M.M.S. Begum, Optimization using central composite design (CCD) for the biosorption of Cr(VI) ions by cross linked chitosan carbonized rice husk (CCACR), Clean Technol Envir, 15, 2013, 293–302.
  • [18] R. Saha, K. Mukherjee, I. Saha, A. Ghosh, S.K. Ghosh, B. Saha, Removal of hexavalent chromium from water by adsorption on mosambi (Citrus limetta) peel, Res Chem Intermed, 39(5), 2013, 2245–2257.
  • [19] Z.A. Al-Othman, R. Ali, M. Naushad, Hexavalent chromium removal from aqueous medium by activated carbon prepared from peanut shell: adsorption kinetics, equilibrium and thermodynamic studies, Chem Eng J, 184, 2012, 238-247.
  • [20] I. Enniya, L. Rghioui, A. Jourani, Adsorption of hexavalent chromium in aqueous solution on activated carbon prepared from apple peels, Sustain Chem Pharm, 7, 2018, 9–16.
  • [21] H. Lata, V.K. Garg, R.K. Gupta, Sequestration of nickel from aqueous solution onto activated carbon prepared from Parthenium hysterophorus L., J Hazard Mater, 157, 2008, 503–509.
  • [22] APHA, Standard Methods for the Examination of Water and Wastewater, 18th ed., American Public Health Association, Washington, DC. 1985.
  • [23] H.P. Boehm, Surface oxides on carbon and their analysis: a critical assessment, Carbon, 40, 2002, 145–149.
  • [24] Y. Chen, B. Wang, J. Xin, P. Sun, D. Wu, Adsorption behavior and mechanism of Cr(VI) by modified biochar derived from Enteromorpha prolifera, Ecotoxicol Environ Saf, 164, 2018, 440–447.
  • [25] R.D.C. Soltani, M. Safari, A. Maleki, R. Rezaee, P. Teymouri, S.E. Hashemi, R. Ghanbari, Y. Zandsalimi, Preparation of Chitosan/Bone Char/Fe3O4 Nanocomposite for Adsorption of Hexavalent Chromium in Aquatic Environments, Arab J Sci Eng, 43, 2018, 5799–5808.
  • [26] N. Rajamohan, M. Rajasimman, M. Dilipkumar, Parametric and kinetic studies on biosorption of mercury using modified Phoenix dactylifera biomass, J Taiwan Inst Chem E, 45, 2014, 2622–2627.
  • [27] I. Langmuir, The adsorption of gases on plane surfaces of glass, mica and platinum, J Am Chem Soc, 40, 1918, 1361–1403.
  • [28] H.M.F. Freundlich, Über die adsorption in lösungen, Z Phys Chem, 57, 1906, 385-470.
  • [29] K.R. Hall, L.C. Eagleton, A. Acrivos, T. Vermeulen, Pore- and solid-diffusion kinetics in fixed-bed adsorption under constant-pattern conditions, Ind Eng Chem Fundam, 5, 1966, 212-223.
  • [30] S. Liu, M. Chen, X. Cao, G. Li, D. Zhang, M. Li, N. Meng, J. Yin, B. Yan, Chromium (VI) removal from water using cetylpyridinium chloride (CPC)-modified montmorillonite, Sep Purif Technol 241, 2020, 116732.
  • [31] S. Liang, S. Shi, H. Zhang, J. Qiu, W. Yu, M. Li, Q. Gan, W. Yu, K. Xiao, B. Liu, One pot solvothermal synthesis of magnetic biochar from waste biomass: formation mechanism and efficient adsorption of Cr(VI) in an aqueous solution, Sci Total Environ, 695, 2019, 133886.
  • [32] W.C. Yang, Q.-Z. Tang, S.Y. Dong, L.Y. Chai, H.Y. Wang, Single-step synthesis of magnetic chitosan composites and application for chromate (Cr(VI)) removal, J Central South Univ, 23, 2016, 317–323.
  • [33] J. Yang, M. Yu, W. Chen, Adsorption of hexavalent chromium from aqueous solution by activated carbon prepared from longan seed: kinetics, equilibrium and thermodynamics, J Ind Eng Chem, 21, 2015, 414–422.
  • [34] I. Enniya, L. Rghioui, A. Jourani, Adsorption of hexavalent chromium in aqueous solution on activated carbon prepared from apple peels, Sustain Chem Pharm, 7, 2018, 9–16.
  • [35] M.H. Dehghani, D. Sanaei, I. Ali, A. Bhatnagar, Removal of chromium(VI) from aqueous solution using treated waste newspaper as a low-cost adsorbent: Kinetic modeling and isotherm studies, J Mol Liq, 215, 2016, 671–679.
  • [36] E. Pehlivan, T. Altun, Biosorption of chromium(VI) ion from aqueous solutions using walnut, hazelnut and almond shell, J Hazard Mater, 155, 2008, 378-384.
  • [37] R. Khalid, Z. Aslam, A. Abbas, W. Ahmad, N. Ramzan, R. Shawabkeh, Adsorptive potential of Acacia nilotica based adsorbent for chromium(VI) from an aqueous phase, Chin J Chem Eng, 26, 2018, 614-622.
  • [38] H. Haroon, T. Ashfaq, S.M.H. Gardazi, T.A. Sherazi, M. Ali, N. Rashid, M. Bilal, Equilibrium kinetic and thermodynamic studies of Cr(VI) adsorption onto a novel adsorbent of Eucalyptus camaldulensis waste: Batch and column reactors, Korean J Chem Eng, 33(10), 2016, 2898-2907.
  • [39] A. Kamari, S.N.M. Yusoff, F. Abdullah, W.P. Putra, Biosorptive removal of Cu(II), Ni(II) and Pb(II) ions from aqueous solutions using coconut dregs residue: Adsorption and characterization studies, J Environ Chem Eng, 2, 2014, 1912-1919.
  • [40] N. Rajamohan, M. Rajasimman, M. Dilipkumar, Parametric and kinetic studies on biosorption of mercury using modified Phoenix dactylifera biomass, J Taiwan Inst Chem E, 45, 2014, 2622–2627.
  • [41] C.P. Tso, C.M. Zhung, Y.H. Shih, Y.M. Tseng, S.C. Wu, R.A. Doong, Stability of metal oxide nanoparticles in aqueous solutions, Water Sci Technol, 61, 2010, 127-133.

Adsorptive removal of Cr(VI) ions from aqueous solutions by H2SO4 modified oak (Quercus L.) sawdust

Year 2020, Volume: 2 Issue: 1, 7 - 14, 23.06.2020

Abstract

In this study, the utilization of H2SO4 modified oak sawdust (Quercus L.) (HMOS) as a new and promising sorbent for the uptake of an extremely toxic inorganic pollutant, Cr(VI) ions, from aqueous media by batch adsorption method has been investigated. The HMOS has been characterized by different methods such as Boehm titration, pHpzc and moisture content. Some of the process parameters including initial solution pH, equilibrium time, initial Cr(VI) concentration, HMOS amount, and salt effect were examined in detail in order to optimize the experimental conditions for the uptake of Cr(VI) ions onto HMOS. The maximum Cr(VI) uptake was achieved at initial solution pH of 2.5 and at equilibrium time of 240 min. The adsorption behaviors of Cr(VI) ions onto both natural oak sawdust (NOS) and HMOS were analyzed in terms of Langmuir and Freundlich isotherm models and the Cr(VI) adsorption was obtained to be compatible with both isotherm models. The Cr(VI) uptake capacities of NOS and HMOS were calculated as 48.07 and 100.0 mg g-1, respectively by utilizing the Langmuir model. As a result, H2SO4 modified oak sawdust provides a versatile alternative to remove Cr(VI) ions from wastewaters.

References

  • [1] J. Wang, D. Zhang, S. Liu, C. Wang, Enhanced removal of chromium(III) for aqueous solution by EDTA modified attapulgite: Adsorption performance and mechanism, Sci Total Environ, 720, 2020, 137391.
  • [2] M. Kazemi, M. Jahanshahi, M. Peyravi, Hexavalent chromium removal by multilayer membrane assisted by photocatalytic couple nanoparticle from both permeate and retentate, J Hazard Mater, 344, 2018, 12-22.
  • [3] Z. Zhao, H. An, J. Lin, M. Feng, V. Murugadoss, T. Ding, H. Liu, Q. Shao, X. Mai, N. Wang, Progress on the photocatalytic reduction removal of chromium contamination, Chem Rec, 19, 2019, 873-882.
  • [4] L. Liu, X. Liu, D. Wang, H. Lin, L. Huang, Removal and reduction of Cr(VI) in simulated wastewater using magnetic biochar prepared by co-pyrolysis of nano-zero-valent iron and sewage sludge, J Clean Prod, 257, 2020,120562.
  • [5] C. Mangwandi, T.A. Kurniawan, A.B. Albadarin, Comparative biosorption of chromium (VI) using chemically modified date pits (CM-DP) and olive stone (CM-OS): Kinetics, isotherms and influence of co-existing ions, Chem Eng Res Des, 156, 2020, 251–262.
  • [6] L. Qin, L. He, W. Yang, A. Lin, Preparation of a novel iron-based biochar composite for removal of hexavalent chromium in water, Environ Sci Pollut Res, 27, 2020, 9214–9226.
  • [7] WHO, 2006, Guidelines for Drinking-Water Quality, 3rd edn, World Health Organization, Geneva, pp. 54.
  • [8] M. Mohsen-Nia, P. Montazeri, H. Modarress, Removal of Cu2+ and Ni2+ from wastewater with a chelating agent and reverse osmosis processes, Desalination, 217, 2007, 276-281.
  • [9] K.Y. Chen, Y.M. Tzou, Y.T. Chan, J.J. Wu, H.Y. Teah, Y.T. Liu, Removal and simultaneous reduction of Cr(VI) by organo-Fe(III) composites produced during coprecipitation and coagulation processes, J Hazard Mater, 376, 2019, 12-20.
  • [10] R. Hans, G. Senanayake, L.C.S. Dharmasiri, J.A.P. Mathes, D.J. Kim, A preliminary batch study of sorption kinetics of Cr(VI) ions from aqueous solutions by a magnetic ion exchange (MIEX) resin and determination of film/pore diffusivity, Hydrometallurgy, 164, 2016, 208–218.
  • [11] M.R. Abukhadra, A. Adlii, B.M. Bakry, Green fabrication of bentonite/chitosan@cobalt oxide composite (BE/CH@Co) of enhanced adsorption and advanced oxidation removal of Congo red dye and Cr (VI) from water, Int J Biol Macromol, 126, 2019, 402-413.
  • [12] D. Ozdes, A. Gundogdu, B. Kemer, C. Duran, M. Kucuk, Assessment of kinetics, thermodynamics and equilibrium parameters of Cr(VI) biosorption onto Pinus brutia Ten, Can J Chem Eng, 92, 2014, 139-147.
  • [13] D. Ozdes, C. Duran, Equilibrium, Kinetics, and Thermodynamic Evaluation of Mercury (II) Removal from Aqueous Solutions by Moss (Homalothecium sericeum) Biomass, Environ Prog Sustain, 34, 2015, 1620-1628.
  • [14] F. Gode, E.D. Atalay, E. Pehlivan, Removal of Cr(VI) from aqueous solutions using modified red pine sawdust, J Hazard Mater, 152, 2008, 1201–1207.
  • [15] R.R. Karri, J.N. Sahu, B.C. Meikap, Improving efficacy of Cr(VI) adsorption process on sustainable adsorbent derived from waste biomass (sugarcane bagasse) with help of ant colony optimization, Ind Crops Prod, 143, 2020, 111927.
  • [16] Y. He, S. Han, H. Lin, Y. Dong, Microwave-Assisted Modification of Corncob with Trimethylammonium Chloride for Efficient Removal of Cr(VI): Preparation, Characterization, and Mechanism, Water Air Soil Pollut, 2020, 231:137.
  • [17] S. Sugashini, K.M.M.S. Begum, Optimization using central composite design (CCD) for the biosorption of Cr(VI) ions by cross linked chitosan carbonized rice husk (CCACR), Clean Technol Envir, 15, 2013, 293–302.
  • [18] R. Saha, K. Mukherjee, I. Saha, A. Ghosh, S.K. Ghosh, B. Saha, Removal of hexavalent chromium from water by adsorption on mosambi (Citrus limetta) peel, Res Chem Intermed, 39(5), 2013, 2245–2257.
  • [19] Z.A. Al-Othman, R. Ali, M. Naushad, Hexavalent chromium removal from aqueous medium by activated carbon prepared from peanut shell: adsorption kinetics, equilibrium and thermodynamic studies, Chem Eng J, 184, 2012, 238-247.
  • [20] I. Enniya, L. Rghioui, A. Jourani, Adsorption of hexavalent chromium in aqueous solution on activated carbon prepared from apple peels, Sustain Chem Pharm, 7, 2018, 9–16.
  • [21] H. Lata, V.K. Garg, R.K. Gupta, Sequestration of nickel from aqueous solution onto activated carbon prepared from Parthenium hysterophorus L., J Hazard Mater, 157, 2008, 503–509.
  • [22] APHA, Standard Methods for the Examination of Water and Wastewater, 18th ed., American Public Health Association, Washington, DC. 1985.
  • [23] H.P. Boehm, Surface oxides on carbon and their analysis: a critical assessment, Carbon, 40, 2002, 145–149.
  • [24] Y. Chen, B. Wang, J. Xin, P. Sun, D. Wu, Adsorption behavior and mechanism of Cr(VI) by modified biochar derived from Enteromorpha prolifera, Ecotoxicol Environ Saf, 164, 2018, 440–447.
  • [25] R.D.C. Soltani, M. Safari, A. Maleki, R. Rezaee, P. Teymouri, S.E. Hashemi, R. Ghanbari, Y. Zandsalimi, Preparation of Chitosan/Bone Char/Fe3O4 Nanocomposite for Adsorption of Hexavalent Chromium in Aquatic Environments, Arab J Sci Eng, 43, 2018, 5799–5808.
  • [26] N. Rajamohan, M. Rajasimman, M. Dilipkumar, Parametric and kinetic studies on biosorption of mercury using modified Phoenix dactylifera biomass, J Taiwan Inst Chem E, 45, 2014, 2622–2627.
  • [27] I. Langmuir, The adsorption of gases on plane surfaces of glass, mica and platinum, J Am Chem Soc, 40, 1918, 1361–1403.
  • [28] H.M.F. Freundlich, Über die adsorption in lösungen, Z Phys Chem, 57, 1906, 385-470.
  • [29] K.R. Hall, L.C. Eagleton, A. Acrivos, T. Vermeulen, Pore- and solid-diffusion kinetics in fixed-bed adsorption under constant-pattern conditions, Ind Eng Chem Fundam, 5, 1966, 212-223.
  • [30] S. Liu, M. Chen, X. Cao, G. Li, D. Zhang, M. Li, N. Meng, J. Yin, B. Yan, Chromium (VI) removal from water using cetylpyridinium chloride (CPC)-modified montmorillonite, Sep Purif Technol 241, 2020, 116732.
  • [31] S. Liang, S. Shi, H. Zhang, J. Qiu, W. Yu, M. Li, Q. Gan, W. Yu, K. Xiao, B. Liu, One pot solvothermal synthesis of magnetic biochar from waste biomass: formation mechanism and efficient adsorption of Cr(VI) in an aqueous solution, Sci Total Environ, 695, 2019, 133886.
  • [32] W.C. Yang, Q.-Z. Tang, S.Y. Dong, L.Y. Chai, H.Y. Wang, Single-step synthesis of magnetic chitosan composites and application for chromate (Cr(VI)) removal, J Central South Univ, 23, 2016, 317–323.
  • [33] J. Yang, M. Yu, W. Chen, Adsorption of hexavalent chromium from aqueous solution by activated carbon prepared from longan seed: kinetics, equilibrium and thermodynamics, J Ind Eng Chem, 21, 2015, 414–422.
  • [34] I. Enniya, L. Rghioui, A. Jourani, Adsorption of hexavalent chromium in aqueous solution on activated carbon prepared from apple peels, Sustain Chem Pharm, 7, 2018, 9–16.
  • [35] M.H. Dehghani, D. Sanaei, I. Ali, A. Bhatnagar, Removal of chromium(VI) from aqueous solution using treated waste newspaper as a low-cost adsorbent: Kinetic modeling and isotherm studies, J Mol Liq, 215, 2016, 671–679.
  • [36] E. Pehlivan, T. Altun, Biosorption of chromium(VI) ion from aqueous solutions using walnut, hazelnut and almond shell, J Hazard Mater, 155, 2008, 378-384.
  • [37] R. Khalid, Z. Aslam, A. Abbas, W. Ahmad, N. Ramzan, R. Shawabkeh, Adsorptive potential of Acacia nilotica based adsorbent for chromium(VI) from an aqueous phase, Chin J Chem Eng, 26, 2018, 614-622.
  • [38] H. Haroon, T. Ashfaq, S.M.H. Gardazi, T.A. Sherazi, M. Ali, N. Rashid, M. Bilal, Equilibrium kinetic and thermodynamic studies of Cr(VI) adsorption onto a novel adsorbent of Eucalyptus camaldulensis waste: Batch and column reactors, Korean J Chem Eng, 33(10), 2016, 2898-2907.
  • [39] A. Kamari, S.N.M. Yusoff, F. Abdullah, W.P. Putra, Biosorptive removal of Cu(II), Ni(II) and Pb(II) ions from aqueous solutions using coconut dregs residue: Adsorption and characterization studies, J Environ Chem Eng, 2, 2014, 1912-1919.
  • [40] N. Rajamohan, M. Rajasimman, M. Dilipkumar, Parametric and kinetic studies on biosorption of mercury using modified Phoenix dactylifera biomass, J Taiwan Inst Chem E, 45, 2014, 2622–2627.
  • [41] C.P. Tso, C.M. Zhung, Y.H. Shih, Y.M. Tseng, S.C. Wu, R.A. Doong, Stability of metal oxide nanoparticles in aqueous solutions, Water Sci Technol, 61, 2010, 127-133.
There are 41 citations in total.

Details

Primary Language English
Subjects Analytical Chemistry
Journal Section Research Articles
Authors

Duygu Özdeş

İbrahim Yıldırım This is me

Celal Duran

Publication Date June 23, 2020
Submission Date April 17, 2020
Acceptance Date May 16, 2020
Published in Issue Year 2020 Volume: 2 Issue: 1

Cite

APA Özdeş, D., Yıldırım, İ., & Duran, C. (2020). Adsorptive removal of Cr(VI) ions from aqueous solutions by H2SO4 modified oak (Quercus L.) sawdust. Turkish Journal of Analytical Chemistry, 2(1), 7-14.
AMA Özdeş D, Yıldırım İ, Duran C. Adsorptive removal of Cr(VI) ions from aqueous solutions by H2SO4 modified oak (Quercus L.) sawdust. TurkJAC. June 2020;2(1):7-14.
Chicago Özdeş, Duygu, İbrahim Yıldırım, and Celal Duran. “Adsorptive Removal of Cr(VI) Ions from Aqueous Solutions by H2SO4 Modified Oak (Quercus L.) Sawdust”. Turkish Journal of Analytical Chemistry 2, no. 1 (June 2020): 7-14.
EndNote Özdeş D, Yıldırım İ, Duran C (June 1, 2020) Adsorptive removal of Cr(VI) ions from aqueous solutions by H2SO4 modified oak (Quercus L.) sawdust. Turkish Journal of Analytical Chemistry 2 1 7–14.
IEEE D. Özdeş, İ. Yıldırım, and C. Duran, “Adsorptive removal of Cr(VI) ions from aqueous solutions by H2SO4 modified oak (Quercus L.) sawdust”, TurkJAC, vol. 2, no. 1, pp. 7–14, 2020.
ISNAD Özdeş, Duygu et al. “Adsorptive Removal of Cr(VI) Ions from Aqueous Solutions by H2SO4 Modified Oak (Quercus L.) Sawdust”. Turkish Journal of Analytical Chemistry 2/1 (June 2020), 7-14.
JAMA Özdeş D, Yıldırım İ, Duran C. Adsorptive removal of Cr(VI) ions from aqueous solutions by H2SO4 modified oak (Quercus L.) sawdust. TurkJAC. 2020;2:7–14.
MLA Özdeş, Duygu et al. “Adsorptive Removal of Cr(VI) Ions from Aqueous Solutions by H2SO4 Modified Oak (Quercus L.) Sawdust”. Turkish Journal of Analytical Chemistry, vol. 2, no. 1, 2020, pp. 7-14.
Vancouver Özdeş D, Yıldırım İ, Duran C. Adsorptive removal of Cr(VI) ions from aqueous solutions by H2SO4 modified oak (Quercus L.) sawdust. TurkJAC. 2020;2(1):7-14.