Study of Complexation Behavior of Lignite Extracted Humic Acid With Some Divalent Cations

Abstract In biogeochemical cycles,humic substances are natural electron shuttles in transforming the nutrients and environmental pollutants. The complexes of humic acid with macro and micro nutrient metals serve as ecofriendly organo-mineral fertilizer. In this study, lignite extracted humic acid-metal (Fe, Mg, Zn) complexes were prepared and characterized. The proximate analysis exhibited the moisture, volatile matter, ash and fixed carbon contents of extracted humic acid of 02.61%, 17.31%, 57.18% and 22.90% respectively. The% metal ions in humic acid complexes ranges from 3.5-7.25%. The FTIR analysis of coal extracted humic acids-metal complexes showed Zn, Mg and Fe ions complexed in bidentate manner predominantly with carboxylic acid moiety of humic acid. Thermal gravimetric analysis indicated the higher value of humic acid decomposition as compared to their metal complexes. The thermal stability observed order is HA- Zn >HA-Fe>HA- Mg. The X-ray diffraction pattern pointed toward the non-crystalline nature of humic acid and their respective complex’s due to having few intense and some small diffuse peaks in the 2θ range from 0 to 80°.Hence the humic acid-metals complexes increase the soil humic content along the availability of essential nutrient that enhance the loam biotic action.