Effect of Atmosphere and Temperature Treatment on Leoanarditefor Increasing Humic Acid Yield

Abstract

Humic acid is a complex molecule including carboxylic, phenolic, alcoholic, and carbonyl fractions in its structure. Addition of this complex structure in soil improves its fertility by increasing its porosity along with water/nutrient capacity. Although naturally exists in soil, humic acid must be added to soil externally in regions with low soil fertility. The present study was conducted to provide insight on improving the efficiency of humic acid yield during its extraction. Leonardite was selected as raw material due to its higher amounts of humic acid compared to low rank coals, soil, agricultural crop residues, compost, sewage sludge, landfill leachate and animal waste. Leonardite was treated at 200, 300 and 400°C, in the presence of air and nitrogen atmospheres and humic acid was extracted from this treated samples. Compared to untreated leonardite, an improvement in humic acid efficiency was achieved for samples treated at 200°C, in the presence of nitrogen atmosphere. The reasons of this distinct behavior in the presence of nitrogen was elaborated with elemental, FT-IR, UV-Vis and XRD analyses.