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.
The distribution of Al, Cd, Cu, Fe, Ni, and Zn among the humic acid, fulvic acid, and precipitable (by adjustment of pH) fractions extracted with 0.5N NaOH from four representative sewage sludges was determined by atomic absorption spectrophotometry. It was found that most of the Al and, with one exception, most of the Fe and Zn were precipitable from the extracted solutions by adjustment of pH in unit intervals between 2.5 and 10.5. Almost all of the Cu was associated with the humic acid fraction. Cd and Ni tended to be associated with the precipitable fraction and with the fulvic acid fraction. Data on the amount of each metal remaining in the extracted solutions as a function of pH suggested that Cd, Ni, and Zn would tend to be the more mobile trace metals in soils affected by application of the sludges investigated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.