Materials For Removal Of Heavy Metals And Dyes From Wastewater

Abstract

Disposal of heavy metals from industrial effluents in natural water bodies have been major preoccupation from many years because of their toxicity towards aquatic life, human beings and the environment. Numerous methods for the wastewater treatments are reported in last two decades. Present study reviews the recent developments, efficiency and usefulness of various methods for the removal of heavy metals from industrial wastewater. From this survey it is found that adsorption in the most helpful and cost effective technique for wastewater treatment of heavy metal contaminated wastewater. Many factors including pH, temperature, initial concentration affects the removal of heavy metals and dyes. So in order to select best adsorbent all these factors should be taken into consideration along with cost of the adsorbent.

Introduction

Nowadays, toxic heavy metals are frequently discharged into the environment in the form of industrial waste water, which causes for soil as well as water pollution1. The waste water directly discharged into natural water bodies is highly harmful to the aquatic ecosystems. The heavy metals like lead, cadmium, and nickel are common metals that cause serious diseases2,3 and disorders in humans and other living beings4. Cadmium metal is highly toxic in nature causing serious diseases like itai itai or ouch ouch from which many of the peoples in Japan are known to suffer as a result of fragility of bones. High concentration of cadmium can leads to the kidney problems1, bone marrow disorders, and anemia. In potable water normal level of Cd is from 0.4 to 60 ppb. Lead inhibits several of the key enzymes involved in overall process of the synthesis whereby the metabolic intermediates accumulates. High levels of Pb in blood (>0.8 ppm) shows symptoms of anemia due to deficiency of hemoglobin. Elevated lead levels (>0.5 to 0.8 ppm) in the blood cause kidney malfunction and brain damage. Another heavy metal nickel and its compounds have been listed by the National Toxicology Programme (NTP) as being reasonably anticipated to be carcinogens. A variety of cancerous and noncancerous respiratory problems such as chronic bronchitis and emphysema have been associated with those exposed to nickel compounds such as welders and foundry workers.

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Heavy metals in industrial wastewater

The discharged heavy metals and dyes from industries in the water bodies has been responsible for the several types of health problems in plant kingdom, animals, and human being5. Evidently it is most important to remove these toxic metals from waste water prior to their discharge into natural water bodies as they are non-biodegradable and persistent.

Cadmium is used in some solder metals and baths used for electroplating. It is also used in Ni-Cd batteries. PVC plastics may contain cadmium stearate as a heat stabilizer. Nickel is used in production of wide range of alloys. Most of the lead goes into battery production and cable covering.

Toxicity

Many heavy metals like lead, cadmium, nickel, zinc, mercury etc. cause serious disorders in human being and other living organisms specially plants and aquatic lives. Some of their toxic effects are listed in Table 1 with their maximum contaminant level(MCL).

Conventional processes for removal

Many conventional methods including flotation, adsorption, chemical precipitation, ion exchange and electrochemical deposition for removals of heavy metals are available. Many heavy metals from industrial waste water are removed by chemical precipitation method. Chemical precipitation is the most widely used for heavy metal removal from inorganic effluent. Most of the heavy metals are removed by forming their hydroxides in alkaline medium as follows, Mn+ + n(OH –) (M(OH)n

Where, M is heavy metal ion and OH – is hydroxyl group from a base which acts as a precipitating agent and M(OH)2is water insoluble hydroxide if heavy metal ion. In order to precipitate the heavy metal it needs highly alkaline pH i.e. pH between 9 and 11.

Adsorption on new adsorbents

In recent years adsorption has become a cost effective technique for removal of heavy metals and dyes form aqueous medium. Basic principal of adsorption is, heavy metals from their solution of aqueous medium are transferred to a solid adsorbent materials and hence can be easily removed from wastewater. Various new adsorbents like red mud6, zeolite 4A prepared from fly ash27, natural Jordanian zeolite8, oak sawdust9, oil shale ash (OSA)10, waste iron oxide11, wheat shells12, Palm kernel fibre13, orange waste14, cancrinite15. Among these methods adsorption is the most effective method for heavy metal ion removal and is extensively used by many workers13,16-19. Different low cost adsorbents like pea fly ash19-21, lime22, activated carbon23,24, bagasse pith25, bagasse fly ash26, soya cake27, slag from blast furnace28, aluminum phosphates29, perlite30, modified kaolinite clay31, brown marine macro algae32, biofilms and associated minerals33, modified lignite fly Ash34, iodate sodalite35 etc. are used by number of workers for the removal of heavy metals. Use of zeolites synthesized from fly ash for applications in the removal of metal species from waste water has been a subject of study for quite some time and various investigations have been made to find the appropriate, efficient, and economical zeolite type36,37.

Thus, it is essential to develop new efficient and cost effective technique to remove dyes from waste water. In last two-three decades many workers have discovered different techniques for dye removal such as electrochemical techniques38, biological processes39 and adsorption. For adsorption number of low cost agricultural and non-agricultural adsorbents are applied in recent years, Banana peel40, neem leaf41, Beech sawdust42, lemon peel43, Aspergillus niger44, fly ash45, glass fibres46 and neem sawdust47.

Some of these materials are less effective for heavy metal removal. Few materials are seems to be more effective and efficient to remove significant amount of heavy metal ions from water48. This extensive literature survey encouraged to develop new material for removal of heavy metal ions. Babel and Kurniawan49 and Bailey50 have reported increasing reviews of the potential of a wide range of low cost sorbents for removal of heavy metals. All these materials may represent substitutes to expensive treatment processes.

Conclusions

In recent few years, large amount of dyes and heavy metals are being discharged in water bodies from industrial effluents causes many serious disorders. The waste water discharged from industries must be treated prior to its discharge in water bodies of a open land. In last two decades many techniques for the waste water treatment including chemical precipitation, ion exchange and electrochemical deposition are used for wastewater treatment. Adsorption is one of the best and cost effective methods for this treatment. Many factors including pH, temperature, initial concentration affects the removal of heavy metals and dyes. So in order to select best adsorbent all these factors should be taken into consideration along with cost of the adsorbent.

References

1. S.H.,Linand R.S. Juang,J. Hazard. Mater., B 92, 315(2002).
2. M.A. Barakat, Arab. J. Chem., , 4, 361(2011).
3. S.Babel, and T.A. Kurniawan, J. Haz. Mat., , B97, 219(2003)
4. V.J.Inglezakis, M.D.Loizidou, and H.P.Grigoropoulou, J. Colloid Interface Sci., 261, 49(2003).
5. J. Mooreand S. Ramamoorty,Appl. Monitor. Assess, Springer-verlag, New York (1984).
6. H. Nadaroglu, M. Kalkan and N. Demir, Desalination, 251, 90(2010).
7. C. Wang, J. Li, X. Sun, L. Wang and X. Sun, J. Environ. Sci., 21, 127(2009).
8. H. M. Baker and A. M. Massadeh, Environ. Monit. Assess, 157, 319(2009).
9. M. E. Argun, E. Dursun, C. Ozdemir and M. Karatas, J. Hazard. Mater., 141, 77(2007).
10. W. Bao, L. Liu, H. Zou, S. Gan, X. Xu, G. Ji, G. Gao andK. Zheng, Chin. J. Chem. Eng., 21, 973(2013).
11. Y. H. Huang, C. L. Hsueh, H. P. Cheng, L. C. Su and C. Y. Chen, J. Hazard. Mater., 144, 406(2007).
12. H. Aydin, Y. Bulut and C. Yerlikaya, J. Environ. Manage., 87, 37(2008).
13. A. E. Ofomaja, J. Environ. Manage., 91, 1491(2010).
14. F. M. Pellera, A. Giannis, D. Kalderis, K. Anastasiadou, R. Stegmann, J. Y. Wang and E. Gidarakos, J. Environ. Manage.96, 35(2012).
15. A. V. Borhade, T. A. Kshirsagar, A. G. Dholi and J. A. Agashe, J. Chem. Eng. Data.,60(3), 586(2015).

16. N. Sapawe, A. A. Jalil, S. Triwahyono, M. I. A. Shah, R. Jusoh, N. F. M. Salleh, B. H. Hameed and A. H. Karim, Chem. Eng. J., 229, 388(2013).