title: Heavy metal removal from sludge with organic chelators: Comparative study of N, N-bis(carboxymethyl) glutamic acid and citric acid.
abstract: The applicability and performance of a new generation of biodegradable chelator, N, N-Bis(carboxymethyl) glutamic acid (GLDA), for extracting heavy metals from sewage sludge was carried out and compared with citric acid (CA). Targeted metals included Cd, Co, Cu, Zn, Ni and Cr, and their contents in the raw sludge were 63.1, 73.4, 1103.2, 2060.3, 483.9 and 604.1 mg kg(-1) (dry sludge basis), respectively. Metals were divided into six fractions including water soluble, exchangeable, carbonates bound, Fe-Mn bound, organic matters bound and residual fraction via chemical fractionation. Washing results showed that in general GLDA exhibited better performance compared with CA, with removal efficiency of 83.9, 87.3, 81.2, 85.6, 89.3 and 90.2% for Cd, Co, Cu, Zn, Ni and Cr, respectively at equilibrium pH = 3.3. Residual metals were better stabilized in the GLAD-washed sludge than in the CA-washed sludge, and were mostly tightly bonded to the residual fraction. Furthermore, CA promoted phosphorus (P) release while GLDA had an opposite effect and tended to retain P within sludge, which could be beneficial for further application in agricultural use. Findings from this study suggested that GLDA could be a potential replacement for refractory and less environmentally-friendly chelators in the extraction of metals from sludge.
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Sciences, Beijing 100049, China; Laboratory of Physical Chemistry, University of Abomey-Calavi, Benin.
authors.forename: Fidèle
authors.initials: F
authors.lastname: Suanon
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Sun
authors.affiliation: Laboratory of Physical Chemistry, University of Abomey-Calavi, Benin; Beninese Center for Scientifics Research and Technologies (CBRST), Cotonou, Benin.
authors.forename: Biaou
authors.initials: B
authors.lastname: Dimon
authors.affiliation: Laboratory of Applied Hydrology, University of Abomey-Calavi, Benin; Laboratory of Inorganic Chemistry and Environment, University of Abomey-Calavi, Benin.
authors.forename: Daouda
authors.initials: D
authors.lastname: Mama
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China. Electronic address: cpyu@iue.ac.cn.
authors.forename: Chang-Ping
authors.initials: CP
authors.lastname: Yu
mesh_terms: D002614:Chelating Agents / Q000737:chemistry*; D005591:Chemical Fractionation; D019343:Citric Acid / Q000737:chemistry*; D005971:Glutamates / Q000737:chemistry*; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry; D019216:Metals, Heavy / Q000032:analysis / Q000737:chemistry*; D012722:Sewage / Q000737:chemistry*; D018505:Waste Management / Q000379:methods
chemical_list: D002614:Chelating Agents; D005971:Glutamates; D019216:Metals, Heavy; C000605118:N,N-bis(carboxymethyl)glutamic acid; D012722:Sewage; D019343:Citric Acid; D005998:Glycine
keywords: Bis(carboxymethyl) glutamic acid; Citric acid; Fractionation; Heavy metals; Sludge