Isolation and Characterization of Humic Acid from Soil Humus from Ahuru Area, Ambon Island, and its Application as Adsorbent for Metal Ions Cu(II) and Pb(II)

Research on the isolation and characterization of humic acid from soil humus in the Ahuru area, Ambon Island, has been conducted. The isolation and purification of humic acid were carried out using an extraction method based on its solubility in a 0.1 M NaOH solution and precipitation in 6 M HCl. Based on the research findings, the humic acid content was determined to be 8.53%. Characterization was performed using an FTIR spectrophotometer to analyze the absorption profile and functional groups present in the isolated humic acid. The characterization results revealed that humic acid contains alcoholic and phenolic OH groups, aromatic C=C, carboxylic C=O, and conjugated alkenes with ketone C=O. The isolated humic acid was then utilized as an adsorbent for Cu(II) and Pb(II) metal ions at an optimum pH of 5, with a contact time of 60 minutes for Cu(II) metal ions and 90 minutes for Pb(II) metal ions. The study results indicated that the adsorption pattern for Cu(II) metal ions followed the Langmuir adsorption isotherm model, with an adsorption capacity of 928.54 mg/g at a concentration of 200 mg/L. Meanwhile, the adsorption capacity of humic acid for Pb(II) metal ions was 795.97 mg/g at a concentration of 200 mg/L.