Gel Filtration Studies of Trace Metal‐Fulvic Acid Solutions Extracted From Sewage Sludges

Abstract

Trace metal‐fulvic acid solutions extracted with NaOH from two chemically different sewage sludges and separated from humic acid using HCl were fractionated on a column of Sephadex G‐10 gel using deionized water at pH 5.65 as the eluant. The effluent from the gel was analyzed in 3‐ml increments for organic C, Cl, and the metals Cd, Cu, Fe, Ni, and Zn. Elution diagrams prepared with the analytical data showed multiple maxima in organic C concentration and a single maximum in Cl concentration (indicating the presence of inorganic salts). Fe and Cu showed concentration maxima that followed closely those in both the organic and inorganic fractions, while Cd, Ni, and Zn tended to show maxima following the inorganic fraction peak and only one or two of the organic C maxima. The data indicated that Cu and Fe formed complexes with sludge‐derived fulvic acid (FA) under the conditions of the experiment. Cd, Ni, and Zn were associated with the FA only weakly, in a manner dependent on the nature of the sludge, and in the relative order of affinity Zn > Ni > Cd. These data suggested that sludge‐derived FA behaves toward trace metals as a relatively harder Lewis base than Cl−.Infrared spectra of the eluted organic fractions indicated that protein decomposition products and polysaccharide components appear in the fractions of relatively larger molecular size, as do the components containing SO3H groups. The IR spectra also gave evidence that COOH and SO3H functional groups are involved in metal‐FA interactions. An important organic fraction of sludge‐derived FA was identified that appears to be an aliphatic, carboxylic acid mixture which can complex only Cu significantly.

Soil organic matter interactions with trace elements

“…At an application rate of 2% sludge, yields and Fe uptake were lower than for the 1.5% rate, indicating that a toxic level had been attained--perhaps with another microelement in the sludge. Bahamet al (9) experimented with gel fIltration of two fulvic acid fractions of sewage sludge (50 and 105 Ilg Fe/g). Elution data showed multiple maxima in organic carbon concentration, a single maximum in Cl concentration, and multiple maxima of Fe concentration which coincided with both the organic carbon and Cl maxima.…”

“…MBA -(M b ) [9] where K is the apparent stability constant for the reaction: nM + L ~ MnL. The MBA (maximum binding ability) was the total binding site concentration as determined by a Langmuir plot of the binding data.…”

Effect of Cadmium on wheat as influenced by lime and manure and its toxic level in plant and soil

“…15 Cd showed little tendency to associate with the fulvic acid fraction of a sewage sludge extract. 16 Primarily, the cationic nature of Cd has been reported by some workers. 17 ' 18 Clearly, there is much controversy in the literature as to the importance and precise nature of the Cd-organic association in soil solutions.…”

Solid-phase distribution of heavy metals as affected by single reagent extraction in dredged sediment derived surface soils

“…That fraction was significantly affected by EDTA extraction for Cu, Pb and Zn, but remained unaffected for the other metals. High extractabilities of Cu, Pb and Zn into EDTA from the oxidisable fraction may be explained by the capability of EDTA to form organometallic complexes, that may compete with the complexing capability of soil organic matter (Baham et al, 1978;Gould and Genetelli, 1978;Brown and Elliott, 1992).…”