Skip to main content

Applications of Titania as a Heterogeneous Catalyst for Degradation of Landfill Leachates

  • Chapter
  • First Online:
Nanocatalysts in Environmental Applications

Part of the book series: Green Energy and Technology ((GREEN))

  • 468 Accesses

Abstract

It is generally needed for globally practiced and cost-effective disposal of municipal solid waste technique. Thus, this chapter focused on applications, modification, and recent development of photocatalysis for municipal solid waste landfill leachate treatment under solar light irradiation. Landfill leachate is generated when municipal solid waste is disposed of essentially because of the percolation of rainwater through the waste decomposition and landfill layers. The direct use of solar radiation is highly attractive for landfill treatments for better cost reduction, synergistic effect, economic aspects reduction of toxicity, decomposition of various pollutants, energy consumption, and environmental concerns. As concerned with photocatalytic technique, several key parameters play an important role to optimize the photocatalytic activities including O2, pH, and biological and chemical oxygen demand ratios. In addition, developing of modified photocatalysis via physical and structural modification methods could considerably simulate the synergistic effects, adsorb natural sunlight, increased oxidation, and benefits on better photodegradation of landfill pollutants. Positive and negative aspects subjected toward the photocatalysis treatment of landfill leachate treatment have been discussed and highlighted coupled with future research trends and outlooks.

This is a preview of subscription content, log in via an institution to check access.

Access this chapter

eBook
USD 16.99
Price excludes VAT (USA)
  • Available as EPUB and PDF
  • Read on any device
  • Instant download
  • Own it forever
Softcover Book
USD 109.99
Price excludes VAT (USA)
  • Compact, lightweight edition
  • Dispatched in 3 to 5 business days
  • Free shipping worldwide - see info
Hardcover Book
USD 109.99
Price excludes VAT (USA)
  • Durable hardcover edition
  • Dispatched in 3 to 5 business days
  • Free shipping worldwide - see info

Tax calculation will be finalised at checkout

Purchases are for personal use only

Institutional subscriptions

Similar content being viewed by others

References

  • Alfano, O. M., Bahnemann, D., Cassano, A. E., Dillert, R., & Goslich, R. (2000). Photocatalysis in water environments using artificial and solar light. Catalysis Today, 58(2), 199–230.

    Article  Google Scholar 

  • Amor, C., De Torres-Socías, E., Peres, J. A., Maldonado, M. I., Oller, I., Malato, S., et al. (2015). Mature landfill leachate treatment by coagulation/flocculation combined with Fenton and solar photo-Fenton processes. Journal of Hazardous Materials, 286, 261–268.

    Article  Google Scholar 

  • Balkaya, N. (1999). A study of optimal experimental conditions in the photocatalytic degradation of an organophosphorous insecticide. Environmental Technology, 20(6), 617–623.

    Article  Google Scholar 

  • Bekbölet, M., Lindner, M., Weichgrebe, D., & Bahnemann, D. W. (1996). Photocatalytic detoxification with the thin-film fixed-bed reactor (TFFBR): Clean-up of highly polluted landfill effluents using a novel TiO2-photocatalyst. Solar Energy, 56(5), 455–469.

    Article  Google Scholar 

  • Cai, F. F., Yang, Z. H., Huang, J., Zeng, G. M., Wang, L. K., & Yang, J. (2014). Application of cetyltrimethylammonium bromide bentonite–titanium dioxide photocatalysis technology for pretreatment of aging leachate. Journal of Hazardous Materials, 275, 63–71.

    Article  Google Scholar 

  • Chang, C. F., & Man, C. Y. (2011). Titania-coated magnetic composites as photocatalysts for phthalate photodegradation. Industrial and Engineering Chemistry Research, 50(20), 11620–11627.

    Article  Google Scholar 

  • Chemlal, R., Abdi, N., Drouiche, N., Lounici, H., Pauss, A., & Mameri, N. (2013). Rehabilitation of Oued Smar landfill into a recreation park: Treatment of the contaminated waters. Ecological Engineering, 51, 244–248.

    Article  Google Scholar 

  • Chen, D., Sivakumar, M., & Ray, A. K. (2000). Heterogeneous photocatalysis in environmental remediation. Developments in Chemical Engineering and Mineral Processing, 8(5–6), 505–550.

    Google Scholar 

  • Cheng, X. T. Z. Y. H., & Shaomin, Z. C. L. (2009). Preparation of supported mixed-crystal titanium dioxide photocatalyst at low temperature and its photocatalytic activity. Chinese Journal of Environmental Engineering, 10, 037.

    Google Scholar 

  • Cho, S. P., Hong, S. C., & Hong, S. I. (2004). Study of the end point of photocatalytic degradation of landfill leachate containing refractory matter. Chemical Engineering Journal, 98(3), 245–253.

    Article  Google Scholar 

  • Cortez, S., Teixeira, P., Oliveira, R., & Mota, M. (2010). Ozonation as polishing treatment of mature landfill leachate. Journal of Hazardous Materials, 182(1), 730–734.

    Article  Google Scholar 

  • Dai, S. S., Liu, J. G., Song, W. C., & Wang, L. L. (2007). Application of advanced treatment for refractory organic wastewater with ozone oxidization method. Water Sciences and Engineering Technology, 2, 24–25.

    Google Scholar 

  • De Morais, J. L., & Zamora, P. P. (2005). Use of advanced oxidation processes to improve the biodegradability of mature landfill leachates. Journal of Hazardous Materials, 123(1), 181–186.

    Article  Google Scholar 

  • De Torres-Socías, E., Prieto-Rodríguez, L., Zapata, A., Fernández-Calderero, I., Oller, I., & Malato, S. (2015). Detailed treatment line for a specific landfill leachate remediation. Brief economic assessment. Chemical Engineering Journal, 261, 60–66.

    Article  Google Scholar 

  • Del Moro, G., Prieto-Rodríguez, L., De Sanctis, M., Di Iaconi, C., Malato, S., & Mascolo, G. (2016). Landfill leachate treatment: Comparison of standalone electrochemical degradation and combined with a novel biofilter. Chemical Engineering Journal, 288, 87–98.

    Article  Google Scholar 

  • Dong, S., Zhang, X., He, F., Dong, S., Zhou, D., & Wang, B. (2015). Visible-light photocatalytic degradation of methyl orange over spherical activated carbon-supported and Er3+: YAlO3-doped Titania in a fluidized bed. Journal of Chemical Technology and Biotechnology, 90(5), 880–887.

    Article  Google Scholar 

  • Fan, X. F., & Liu, J. M. (2015). Graphene-supported CoPc/Titania synthesized by sol-gel–hydrothermal method with enhanced photocatalytic activity for degradation of the typical gas of landfill exhaust. Journal of the Air and Waste Management Association, 65(1), 50–58.

    Article  MathSciNet  Google Scholar 

  • Ghani, Z. A., Yusoff, M. S., & Andas, J. (2015, October). Review on Applications of Nanoparticles in Landfill Leachate Treatment. In Applied mechanics and materials (Vol. 802, pp. 525–530). Trans Tech Publications.

    Google Scholar 

  • Ghodbane, H., Hamdaoui, O., Vandamme, J., Van Durme, J., Vanraes, P., Leys, C., & Nikiforov, A. Y. (2015). Degradation of AB25 dye in liquid medium by atmospheric pressure non-thermal plasma and plasma combination with photocatalyst Titania. Open Chemistry, 13(1).

    Google Scholar 

  • Ghosh, S., Kouamé, N. A., Ramos, L., Remita, S., Dazzi, A., Deniset-Besseau, A., et al. (2015). Conducting polymer nanostructures for photocatalysis under visible light. Nature Materials, 14(5), 505–511.

    Article  Google Scholar 

  • Gulyas, H., Bockelmann, D., Hemmerling, L., Bahnemann, D., & Sekoulov, I. (1994). Treatment of recalcitrant organic compounds in oil reclaiming wastewater by ozone/hydrogen peroxide and UV/titanium dioxide. Water Science and Technology, 29(9), 129–132.

    Google Scholar 

  • Hermosilla, D., Merayo, N., Ordóñez, R., & Blanco, Á. (2012). Optimization of conventional Fenton and ultraviolet-assisted oxidation processes for the treatment of reverse osmosis retentate from a paper mill. Waste Management, 32(6), 1236–1243.

    Article  Google Scholar 

  • Hilles, A. H., Amr, S. S. A., Hussein, R. A., El-Sebaie, O. D., & Arafa, A. I. (2016). Performance of combined sodium persulfate/H2O2 based advanced oxidation process in stabilized landfill leachate treatment. Journal of Environmental Management, 166, 493–498.

    Article  Google Scholar 

  • Hirakawa, T., Kominami, H., Ohtani, B., & Nosaka, Y. (2001). Mechanism of photocatalytic production of active oxygens on highly crystalline Titania particles by means of chemiluminescent probing and ESR spectroscopy. The Journal of Physical Chemistry B, 105(29), 6993–6999.

    Article  Google Scholar 

  • Hirakawa, T., & Nosaka, Y. (2002). Properties of O2-and OH formed in Titania aqueous suspensions by photocatalytic reaction and the influence of H2O2 and some ions. Langmuir, 18(8), 3247–3254.

    Article  Google Scholar 

  • Hu, L., Zeng, G., Chen, G., Dong, H., Liu, Y., Wan, J., et al. (2016). Treatment of landfill leachate using immobilized Phanerochaete chrysosporium loaded with nitrogen-doped TiO2 nanoparticles. Journal of Hazardous Materials, 301, 106–118.

    Article  Google Scholar 

  • Huang, H., Lin, J., Fan, L., Wang, X., Fu, X., & Long, J. (2015). Heteroatomic Ni, Sn clusters-grafted anatase Titania photocatalysts: Structure, electron delocalization, and synergy for solar hydrogen production. The Journal of Physical Chemistry C, 119(19), 10478–10492.

    Article  Google Scholar 

  • Huang, J., Nkrumah, P. N., Li, Y., & Appiah-Sefah, G. (2013). Chemical behavior of phthalates under abiotic conditions in landfills. In Reviews of environmental contamination and toxicology (Vol. 224, pp. 39–52). Springer New York.

    Google Scholar 

  • Kaneva, N., Stambolova, I., Blaskov, V., Eliyas, A., & Vassilev, S. (2013). Microwave-assisted and conventional sol-gel preparation of photocatalytically active ZnO/Titania/glass multilayers. Open Chemistry, 11(7), 1055–1065.

    Article  Google Scholar 

  • Karaca, G., Baskaya, H. S., & Tasdemir, Y. (2016). Removal of polycyclic aromatic hydrocarbons (PAHs) from inorganic clay mineral: Bentonite. Environmental Science and Pollution Research, 23(1), 242–252.

    Article  Google Scholar 

  • Kumar, M. G., Ishii, S., Müller, T. S., Itoh, K., & Murabayashi, M. (1999). Treatment of textile dye wastewater using ozone combined with photocatalyst. Toxicological and Environmental Chemistry, 68(1–2), 221–231.

    Article  Google Scholar 

  • Lee, C. M., Palaniandy, P., Zaman, N. Q., & Adlan, M. N. (2015, October). Pharmaceutical removal from synthetic wastewater using heterogeneous-photocatalyst. In Applied mechanics and materials (Vol. 802, pp. 507–512). Trans Tech Publications.

    Google Scholar 

  • Li, S., Cao, X., Liu, L., & Ma, X. (2015). Degradation of thiamethoxam in water by the synergy effect between the plasma discharge and the Titania photocatalysis. Desalination and Water Treatment, 53(11), 3018–3025.

    Article  Google Scholar 

  • Liu, F., He, T., Cao, Q., Xu, Y., Liu, W., & Zhou, W. (2015a). Structure and property of nano-Titania doped with Ag+ membrane photocatalyst. Journal of Nanoscience and Nanotechnology, 15(4), 2726–2732.

    Article  Google Scholar 

  • Liu, G. Q., Chen, L., Wang, Y. P., & Peng, P. Y. (2015b). Photodegradation of 2-naphthalenesulfonate in aqueous catalyzed by N-doped Titania under irradiation of simulated solarlight. In Specialized collections (Vol. 2, pp. 1201–1205). Trans Tech Publications.

    Google Scholar 

  • Liu, T. X., Li, X. Z., & Li, F. B. (2010). Development of a photocatalytic wet scrubbing process for gaseous odor treatment. Industrial and Engineering Chemistry Research, 49(8), 3617–3622.

    Article  Google Scholar 

  • Liu, Z., Wu, W., Shi, P., Guo, J., & Cheng, J. (2015c). Characterization of dissolved organic matter in landfill leachate during the combined treatment process of air stripping, Fenton, SBR and coagulation. Waste Management, 41, 111–118.

    Article  Google Scholar 

  • Merabet, S., Bouzaza, A., & Wolbert, D. (2009). Photocatalytic degradation of indole in a circulating upflow reactor by UV/TiO2 process—Influence of some operating parameters. Journal of Hazardous Materials, 166(2), 1244–1249.

    Article  Google Scholar 

  • Miaomiao, P. L. J. M. W. (2008). Advanced treatment of landfill leachate by the combined use of photocatalysis and ozonation. Chinese Journal of Environmental Engineering, 5, 019.

    Google Scholar 

  • Moon, G. H., Kim, W., Bokare, A. D., Sung, N. E., & Choi, W. (2014). Solar production of H2O2 on reduced graphene oxide–Titania hybrid photocatalysts consisting of earth-abundant elements only. Energy & Environmental Science, 7(12), 4023–4028.

    Article  Google Scholar 

  • Moreira, F. C., Soler, J., Fonseca, A., Saraiva, I., Boaventura, R. A., Brillas, E., et al. (2015). Incorporation of electrochemical advanced oxidation processes in a multistage treatment system for sanitary landfill leachate. Water Research, 81, 375–387.

    Article  Google Scholar 

  • Obata, K., Kishishita, K., Okemoto, A., Taniya, K., Ichihashi, Y., & Nishiyama, S. (2014). Photocatalytic decomposition of NH3 over TiO2 catalysts doped with Fe. Applied Catalysis, B: Environmental, 160, 200–203.

    Article  Google Scholar 

  • Pichat, P. (2016). Fundamentals of Titania photocatalysis. Consequences for some environmental applications. In Heterogeneous photocatalysis (pp. 321–359). Springer, Berlin, Heidelberg.

    Google Scholar 

  • Piscopo, A., Robert, D., & Weber, J. V. (2001). Influence of pH and chloride anion on the photocatalytic degradation of organic compounds: Part I. Effect on the benzamide and para-hydroxybenzoic acid in Titania aqueous solution. Applied Catalysis, B: Environmental, 35(2), 117–124.

    Article  Google Scholar 

  • Poblete, R., Otal, E., Vilches, L. F., Vale, J., & Fernández-Pereira, C. (2011). Photocatalytic degradation of humic acids and landfill leachate using a solid industrial by-product containing TiO2 and Fe. Applied Catalysis, B: Environmental, 102(1), 172–179.

    Article  Google Scholar 

  • Poblete, R., Prieto-Rodríguez, L., Oller, I., Maldonado, M. I., Malato, S., Otal, E., … & Fernández-Pereira, C. (2012). Solar photocatalytic treatment of landfill leachate using a solid mineral by-product as a catalyst. Chemosphere, 88(9), 1090–1096.

    Google Scholar 

  • Poznyak, T., Bautista, G. L., Chaírez, I., Córdova, R. I., & Ríos, L. E. (2008). Decomposition of toxic pollutants in landfill leachate by ozone after coagulation treatment. Journal of Hazardous Materials, 152(3), 1108–1114.

    Article  Google Scholar 

  • Qiang, C. H. E. N. (2009). Progress in effect of inorganic ions on photocatalysis reaction by use of TiO2. Journal of Anhui Agricultural Sciences, 25, 129.

    Google Scholar 

  • Rashed, M. N. (2015). Photocatalytic degradation of divalent metals under sunlight irradiation using nanoparticle titania modified concrete materials (recycled glass cullet). In Recent progress in desalination, environmental and marine outfall systems (pp. 93–108). Springer International Publishing.

    Google Scholar 

  • Reddy, K. R., Hassan, M., & Gomes, V. G. (2015). Hybrid nanostructures based on titanium dioxide for enhanced photocatalysis. Applied Catalysis, A: General, 489, 1–16.

    Article  Google Scholar 

  • Rocha, E. M., Vilar, V. J., Fonseca, A., Saraiva, I., & Boaventura, R. A. (2011). Landfill leachate treatment by solar-driven AOPs. Solar Energy, 85(1), 46–56.

    Article  Google Scholar 

  • Sekine, K., Yamamoto, H., Kono, S., Ikeda, T., Kuroda, A., & Tanii, T. (2015). Surface modification of cell scaffold in aqueous solution using TiO2 photocatalysis and linker protein L2 for patterning primary neurons. e-Journal of Surface Science and Nanotechnology, 13, 213–218.

    Article  Google Scholar 

  • Sotelo-Vazquez, C., Noor, N., Kafizas, A., Quesada-Cabrera, R., Scanlon, D. O., Taylor, A., et al. (2015). Multifunctional P-doped Titania films: A new approach to self-cleaning, transparent conducting oxide materials. Chemistry of Materials, 27(9), 3234.

    Article  Google Scholar 

  • Srivastava, A. (2015). Photocatalytic application of titanium dioxide in architectural concrete: A review. International Journal of Scientific Research & Chemical Engineering, 1(1).

    Google Scholar 

  • Tauchert, E., Schneider, S., de Morais, J. L., & Peralta-Zamora, P. (2006). Photochemically-assisted electrochemical degradation of landfill leachate. Chemosphere, 64(9), 1458–1463.

    Article  Google Scholar 

  • Thiruvenkatachari, R., Ouk Kwon, T., & Shik Moon, I. (2005). Application of slurry type photocatalytic oxidation-submerged hollow fiber microfiltration hybrid system for the degradation of bisphenol A (BPA). Separation Science and Technology, 40(14), 2871–2888.

    Article  Google Scholar 

  • Trabelsi, H., Atheba, G. P., Hentati, O., Mariette, Y. D., Robert, D., Drogui, P., et al. (2016). Solar photocatalytic decolorization and degradation of methyl orange using supported Titania. Journal of Advanced Oxidation Technologies, 19(1), 79–84.

    Article  Google Scholar 

  • Venkatadri, R., & Peters, R. W. (1993). Chemical oxidation technologies: Ultraviolet light/hydrogen peroxide, Fenton’s reagent, and titanium dioxide-assisted photocatalysis. Hazardous Waste and Hazardous Materials, 10(2), 107–149.

    Article  Google Scholar 

  • Vilar, V. J., Capelo, S. M., Silva, T. F., & Boaventura, R. A. (2011a). Solar photo-Fenton as a pre-oxidation step for biological treatment of landfill leachate in a pilot plant with CPCs. Catalysis Today, 161(1), 228–234.

    Article  Google Scholar 

  • Vilar, V. J., Rocha, E. M., Mota, F. S., Fonseca, A., Saraiva, I., & Boaventura, R. A. (2011b). Treatment of a sanitary landfill leachate using combined solar photo-Fenton and biological immobilized biomass reactor at a pilot scale. Water Research, 45(8), 2647–2658.

    Article  Google Scholar 

  • Wang, D., Duan, Y., Luo, Q., Li, X., An, J., Bao, L., et al. (2012). Novel preparation method for a new visible light photocatalyst: Mesoporous Titania supported Ag/AgBr. Journal of Materials Chemistry, 22(11), 4847–4854.

    Article  Google Scholar 

  • Wang, J., Ma, X. P., Tang, F. D., Yang, C. L., Li, Y., & Guo, B. (2011). Study on pretreatment of landfill leachate by microwave-assisted catalytic oxidation process. China Environmental Science, 31(7), 1166–1170.

    Google Scholar 

  • Wang, Z. P., Zhang, Z., Lin, Y. J., Deng, N. S., Tao, T., & Zhuo, K. (2002). Landfill leachate treatment by a coagulation–photooxidation process. Journal of Hazardous Materials, 95(1), 153–159.

    Article  Google Scholar 

  • Wiszniowski, J., Robert, D., Surmacz-Gorska, J., Miksch, K., Malato, S., & Weber, J. V. (2004). Solar photocatalytic degradation of humic acids as a model of organic compounds of landfill leachate in pilot-plant experiments: Influence of inorganic salts. Applied Catalysis, B: Environmental, 53(2), 127–137.

    Article  Google Scholar 

  • Wiszniowski, J., Robert, D., Surmacz-Gorska, J., Miksch, K., & Weber, J. V. (2006a). Landfill leachate treatment methods: A review. Environmental Chemistry Letters, 4(1), 51–61.

    Article  Google Scholar 

  • Wiszniowski, J., Robert, D., Surmacz-Gorska, J., Miksch, K., & Weber, J. V. (2006b). Leachate detoxification by combination of biological and Titania-photocatalytic processes. Water Science and Technology, 53(3), 181–190.

    Article  Google Scholar 

  • Wu, T. T., Xie, Y. P., Yin, L. C., Liu, G., & Cheng, H. M. (2014). Switching photocatalytic H2 and O2 generation preferences of rutile Titania microspheres with dominant reactive facets by boron doping. The Journal of Physical Chemistry C, 119(1), 84–89.

    Article  Google Scholar 

  • Xiang, Q., Yu, J., & Jaroniec, M. (2012). Synergetic effect of MoS2 and graphene as cocatalysts for enhanced photocatalytic H2 production activity of Titania nanoparticles. Journal of the American Chemical Society, 134(15), 6575–6578.

    Article  Google Scholar 

  • Xiaofeng, G., Minfei, J., Chunying, L., & Zhenhui, Z. (2003). Photocatalytic oxidation of landfill leachate on titanium dioxide membrane loaded on fiberglass cloth. Chongqing Environmental Science, 11, 023.

    Google Scholar 

  • Yang, Y. H., & Wang, J. S. (2004). Photocatolysis in degradation of environmental pollutants Using TiO2. Journal of Gansu Sciences, 3, 010.

    Google Scholar 

  • Yu, H., Irie, H., Shimodaira, Y., Hosogi, Y., Kuroda, Y., Miyauchi, M., et al. (2010). An efficient visible-light-sensitive Fe(III)-grafted Titania photocatalyst. The Journal of Physical Chemistry C, 114(39), 16481–16487.

    Article  Google Scholar 

  • Zhang, J., Zhu, H. H., Lei, K. C., & Quan, H. (2014, April). Study on photocatalytic degradation performance of nano carbon load WO3 doping Titania composites. In Advanced materials research (Vol. 881, pp. 901–904).

    Google Scholar 

  • Zhang, P. Y., Yu, G., Sun, H. T., Jiang, Z. P., & China, E. S. (2000). Preliminary study on the degradation of organic compound by integrated ozone/activated carbon. China Environmental Science-Chinese Edition, 20(2), 159–162.

    Google Scholar 

  • Zhou, C., Gong, Z., Hu, J., Cao, A., & Liang, H. (2015a). A cost-benefit analysis of landfill mining and material recycling in China. Waste Management, 35, 191–198.

    Article  Google Scholar 

  • Zhou, N., López-Puente, V., Wang, Q., Polavarapu, L., Pastoriza-Santos, I., & Xu, Q. H. (2015b). Plasmon-enhanced light harvesting: applications in enhanced photocatalysis, photodynamic therapy and photovoltaics. RSC Advances, 5(37), 29076–29097.

    Article  Google Scholar 

  • Zhou, X., Zheng, Y., Zhou, J., & Zhou, S. (2015c). Degradation kinetics of photoelectrocatalysis on landfill leachate using codoped TiO2/Ti photoelectrodes. Journal of Nanomaterials, 2015, 7.

    Google Scholar 

  • Zhuang, J. J., Xiang, N., Lu, X. Y., Xiang, B., Xiong, Y., & Song, R. G. (2015). Improved photocatalytic activity of cerium doped Titania films prepared by microarc oxidation. Materials Technology: Advanced Performance Materials, 1753555715Y–0000000072.

    Google Scholar 

Download references

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Nurhidayatullaili Muhd Julkapli .

Rights and permissions

Reprints and permissions

Copyright information

© 2018 Springer International Publishing AG

About this chapter

Check for updates. Verify currency and authenticity via CrossMark

Cite this chapter

Muhd Julkapli, N., Bagheri, S. (2018). Applications of Titania as a Heterogeneous Catalyst for Degradation of Landfill Leachates. In: Nanocatalysts in Environmental Applications. Green Energy and Technology. Springer, Cham. https://doi.org/10.1007/978-3-319-69557-0_4

Download citation

  • DOI: https://doi.org/10.1007/978-3-319-69557-0_4

  • Published:

  • Publisher Name: Springer, Cham

  • Print ISBN: 978-3-319-69556-3

  • Online ISBN: 978-3-319-69557-0

  • eBook Packages: EnergyEnergy (R0)

Publish with us

Policies and ethics