Extraction and charactrisation of humic acid from different organic wastes and its physico-chemical properties

Abstract

A study on characterization and extraction of humic acid collected from various agro-industrial and agricultural organic wastes from different locations viz., cocopeat, coffee pulp, pressmud, biofuel waste, distillery biocompost, sewage sludge, poultry manure, vermicompost, urban compost and farm yard manure (FYM). Results revel that physical properties such as bulk density and water holding capacity of different organic wastes ranged from 0.22 Mg m-3 (85.50 %) in coco peat to 0.69 Mg m-3 (40.21%) of biofuel waste. Chemical properties like pH of poultry manure (pH 8.32) were alkaline in nature and biofuel waste (pH 5.28) slightly acidic in nature. Electrical conductivity was high 1.89 dSm-1in coffee pulp followed by FYM 1.50 dS m-1. Organic carbon content was higher (40.99%) in biofuel waste. While it was lowest (14.13%) in sewage sludge. With respect to major and secondary nutrients poultry manure recorded higher total N, P, K and Ca (2.85, 1.56, 1.92 and 3.89 %) and iron, manganese, copper and zinc(3850, 541.30, 76 and 476 mg kg-1 respectively). Higher recovery of humic and fulvic acid, (8.92 and 4.21 %, respectively) was recorded in press mud and lowest was in coco peat with 3.43 and 2.45 per cent, respectively. Elemental composition (CHNO) of humic acid extracted from poultry manure had higher N (6.01 %) followed by pressmud and coffee pulp. Higher C (61.04 %) and H (8.89%) were recorded in biofuel waste and O (52.31 %) was higher in sewage sludge. Carboxyl (6.08 meq g-1), phenolic hydroxyl (1.94 meq g-1) groups and total acidity (8.02 meq g-1) was higher in poultry manure followed by pressmud and coffee pulp. However, lower content of carboxyl (2.84 meq g-1) phenolic hydroxyl group (1.32 meq g-1) and total acidity (4.16 meq g-1) was observed in biofuel waste. Slightly higher concentration of nickel (21.8 mg kg-1) and chromium (17 mg kg-1) was observed in humic acid of sewage sludge.