Study of complexation of lead, chromium, manganese and zinc with fulvic acid extracted from battery–contaminated soil

Abstract

Humic substances are considered as the most important part of soil. Different types of humic substances are humic acid (HA), fulvic acid (FA) and humate. Humic substances (HS) are produced from microbial degradation, chemical polymerization and oxidation of organic matter generated from plants and animals. Both composition and structure of humic substances(HS) are different from each local area to other and characterizations such as XRF, EDX-SEM, FTIR and NMR exhibit better understanding of their impact on soil chemistry. Due to polyfunctionality, HS have many different functional groups. FA is lighter and more soluble compare to HA and plays a vital role to transport chemical species. HS work as the most powerful chelating agents among natural organic substances. Only a few scientific literatures are found on HA-metal interaction in Bangladesh and none on FA-metals interactions. FA are extracted by alkali treatment from battery waste contaminated (BWC) and Tangoar haor (TA) region soil. The structure and composition of FA extracted from soil of the TA and BWC region are not well studied. The quantity of metal in the FA fractions was determined. It is found that FA from the BWC soil contain more metal than FA from the TA soil.

Soil experiments of metal/FA complexes showed that FA fractions have the best precipitation ability for heavy metals. The obtained results suggested that FA contain

mainly phenolic, methyl, carboxylic, carbonyl functional groups with smaller amount of sugars and nitrogen bases attached to a fused aromatic backbone. These functional groups allow them to interact with metal ions and complex formation. Metal-FA can influence removal and transportation of heavy metal from soil and water. During this study the ability of FA (isolated from BWC) to reduce toxic metals’ concentration of contaminated water was examined. More specifically, the effect of these compounds was tested on water contaminated (at various concentrations) with Mn, Zn, Cr and Pb. Therefore the knowledge of FA composition and complexation with metals will help us to understand the application in metal removal.