scholarly journals Chemical and Biological Leaching Methods to Remove Heavy Metals from Sewage Sludge: A Review

2008 ◽  
Vol 4 (3) ◽  
pp. 509-517
Author(s):  
Lugard N. Ukiwe ◽  
Allinor J.I ◽  
Ejele A.E ◽  
Anyadiegwu C.I.C ◽  
Ibeneme S.I

The removal of heavy metals (HMs) in sewage sludge (SS) is important since sludge is often disposed or applied on farmland to enhance soil fertility. The present study reviewed two conceptual approaches (chemical and biological leaching) of removing HMs present in SS. In the chemical leaching method, traditional acid treatment together with novel methods such as aeration, complexation and sequential extraction procedure have been reviewed extensively. Certain factors influence the removal of HMs in SS. These factors include; pH, leaching agent, redox potential, and contact time. Nitric acid (HNO3), hydrochloric acid (HCl), sulphuric acid (H2SO4), phosphoric acid (H3PO4), ethylenediamine tetraacetic acid (EDTA), as well as Thiobacillus thiooxidans and Thiobacillus ferrooxidans are the most widely studied leaching agents and substrates involved in the chemical and bioleaching processes. However, the bioleaching process has been proposed as a safe, efficient, economical, environmental friendly method to remove HMs in SS due to its simplicity, high yield of metal extraction, low acid consumption, and low sludge solids concentration. Nevertheless, the present review has noted that most researchers are of the opinion that more studies are needed in the bioleaching method in order to enhance its commercial attraction.  

2019 ◽  
Vol 10 (2) ◽  
pp. 169-178
Author(s):  
A* Azhdarpoor ◽  
R Hoseini ◽  
M Dehghani ◽  
◽  
◽  
...  

Author(s):  
Kanghee Cho ◽  
Eunji Myung ◽  
Hyunsoo Kim ◽  
Cheonyoung Park ◽  
Nagchoul Choi ◽  
...  

In this study, we investigated the feasibility of using a solution of sulfuric acid and phosphoric acid as an extraction method for soil-washing to remove Cu, Pb, Zn, and As from contaminated soil. We treated various soil particles, including seven fraction sizes, using sulfuric acid. In addition, to improve Cu, Pb, Zn, and As removal efficiencies, washing agents were compared through batch experiments. The results showed that each agent behaved differently when reacting with heavy metals (Cu, Pb, and Zn) and As. Sulfuric acid was more effective in extracting heavy metals than in extracting As. However, phosphoric acid was not effective in extracting heavy metals. Compared with each inorganic acid, As removal from soil by washing agents increased in the order of sulfuric acid (35.81%) < phosphoric acid (62.96%). Therefore, an enhanced mixture solution using sulfuric acid and phosphoric acid to simultaneously remove heavy metals and As from contaminated soils was investigated. Sulfuric acid at 0.6 M was adopted to combine with 0.6 M phosphoric acid to obtain the mixture solution (1:1) that was used to determine the effect for the simultaneous removal of both heavy metals and As from the contaminated soil. The removal efficiencies of As, Cu, Pb, and Zn were 70.5%, 79.6%, 80.1%, and 71.2%, respectively. The combination of sulfuric acid with phosphoric acid increased the overall As and heavy metal extraction efficiencies from the contaminated soil samples. With the combined effect of dissolving oxides and ion exchange under combined washings, the removal efficiencies of heavy metals and As were higher than those of single washings.


2006 ◽  
Vol 54 (9) ◽  
pp. 129-135 ◽  
Author(s):  
D. del Mundo Dacera ◽  
S. Babel

Recent studies revealed that organic acids such as citric and oxalic acids seemed to be more promising as chemical extracting agents for removal of heavy metals from contaminated sludge, since they are biodegradable and can attain a higher metal extraction efficiency at mildly acidic pH compared to other extracting agents. Results of a lab-scale study on the efficiency of citric acid in the extraction of chromium (Cr), copper (Cu), lead (Pb), nickel (Ni) and zinc (Zn) from anaerobically digested sludge, revealed that citric acid seemed to be highly effective in extracting Cr (at 100%), Cu (at 88%), Ni (at 98%) and Zn (at 100%) at pH 2.33, mostly at 5 days leaching time except for Cu and Zn, which are at 1 day and 2 h contact times respectively. Lead removal at the same pH was also high at 95% but at a longer leaching time of 11 days. At pH 3, citric acid seemed to be highly effective in extracting Pb (at 100%) at 1 day leaching time, although higher removals were also attained for Ni (70%) and Zn (80%) at only 2 h leaching time. Chemical speciation studies showed that Cr, Cu and Ni in the sludge sample seem to predominate in residual fractions, while Pb and Zn were found mostly bound to organic and inorganic matter forms, hence the potential of the sludge for land application.


2009 ◽  
Vol 163 (2-3) ◽  
pp. 1157-1164 ◽  
Author(s):  
Muhammad K. Jamali ◽  
Tasneem G. Kazi ◽  
Muhammad B. Arain ◽  
Hassan I. Afridi ◽  
Nusrat Jalbani ◽  
...  

2007 ◽  
Vol 141 (1) ◽  
pp. 202-208 ◽  
Author(s):  
Yun-Guo Liu ◽  
Ming Zhou ◽  
Guang-Ming Zeng ◽  
Xin Li ◽  
Wei-Hua Xu ◽  
...  

Desalination ◽  
2009 ◽  
Vol 239 (1-3) ◽  
pp. 46-57 ◽  
Author(s):  
M. Otero ◽  
F. Rozada ◽  
A. Morán ◽  
L.F. Calvo ◽  
A.I. García

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