3,3'-dichlorobenzidine dihydrochloride

Adsorption / desorption

Administrative data

Endpoint:

adsorption / desorption

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

other information

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: secondary source

Data source

Reference

Reference Type:

secondary source

Title:

BUA, Beratergremium für umweltrelevante Altstoffe; 3,3´-Dichlrorobenzidin, BUA-Stoffbericht 30, March 1989

Year:

1989

Bibliographic source:

Gesellschaft Deutscher Chemiker, GdCh, Beratergremium für umweltrelevante Altstoffe, BUA, VCH Verlag, Weinheim

Materials and methods

Test material

Test material information

Constituent 1

Reference substance name:

3,3'-dichlorobenzidine

EC Number:

202-109-0

EC Name:

3,3'-dichlorobenzidine

Cas Number:

91-94-1

IUPAC Name:

3,3'-dichlorobiphenyl-4,4'-diamine

Applicant's summary and conclusion

Executive summary:

3,3´-dichlorobenzidine (DCB) is readily adsorbed by aquatic sediments.

As was found for sand-silt sediments from ponds with an organic carbon content of 0.8 - 2.4% , the sediment-water partition coefficient K_d after 24 hours incubation at 22°C for both, destilled water or to pH 5 - 7 buffered solutions were between 20 - 40 (K_d as the ratio of sediment sorbed DCB [µg/g sediment] to dissolved DCB [µg/g water]). Lake sediments with extremely high organic carbon content showed K_d-values up to 128.

With more alkaline pH, especially at pH 9, sorption is considerably declining as desorption is increased. This is due to the liberation of humic acids and fulvo acids from the sediment. The extent of desorption is declining with prolonged contact time of sediment with DCB (24h versus 7 days). This might be so because of a transition with time of mainly phyisical adsoprtion to covalent bonds

by condensation reactions of amino groups of DCB with carbonyl groups of the organic carbon content of the sediment.

This is supported by other data showing the decrease with time of the extractability of DCB from clay-loam-soils by ethyl acetate : methanol 60 : 40 (v/v) (4 weeks: 22%, 32 weeks: 7 - 10%) and the concommitant increase of extractability with sodium hydroxide.

Immobility of DCB in soils was also demonstrated by perlocation experiments (constant water flow through DCB conatminated soil to noncontaminated soil over 12 weeks): at maximum 2.9% of the radioactively labelled DCB had been translocated to the noncontaminated soil and at maximum 0.16% had been found in the flow through water.

Adsorption of DCB to soils is following Freundlich´s equation, as had been deduced with clay-loam-soil and sand soil:

C_s = K_p * C_W^1/n;

C_s = amount of DCB adsorbed to soil [nmol/g];

C_W = DCB in solution water [nmol/ml];

K_P = Soil-watre partition coefficient;

Constant 1/n describes linearity of the adsorption isotherm;

Clay-loam (5.69% organic carbon, pH 7.7, 25°C): K_P = 1113, 1/n = 0,85

Sand (2.9% organic carbon, pH 5.9, 25°C): K_P = 273, 1/n = 0,74

This demonstrates the high affinity of DCB for both soils.