EFFECT OF HUMIC ACID ON COPPER BIOSORPTION BY ...

The research focused on the effect of humic acid (HA) on the distribution of Cu in Cu-HA-Teak leaf powder system. The experiment was carried out by varying the initial mass of Cu (MCu) in the system at a temperature of 310K. The experiment was carried out independently at pH 4, 6, and 10. The data obtained revealed that the concentration of copper in the solution phase of the system decreases with pH. It was also noted that a relationship exist between the initial mass of copper in the system and the extent of copper binding to the powdered leaf at all pH. And pH increased with the extent of Cu binding to the leaf powder (P). The mass of copper bound ligand (humic acid) in the solid phase was noted to vary with pH. The partition constant (KD) was observed to increase MCu. The analysis revealed that the partition constant for organic acid (KL) and KD increases with increase in pH. HA was noted to promote the transfer of Cu from solution to solid phase. The analysis suggested that the strong relationship between KD and KL reveals the dependence of KD on HA, and this was effectively proved using the Ligand Complex Partition Effect Model. The model indicated that the properties of humic substance which makes it capable of influencing trace metal distribution are hydrophobicity, detergent properties and metal complexing ability. The ability of ligands to exist in solution and solid phases simultaneously is therefore crucial in biosorption studies.