The Preparation of Humic Acid from Poly(vinyl chloride)

Abstract

Humic acid was obtained in excellent yield by oxidation of the char, which was derived from poly (vinyl chloride) (PVC) by thermal decomposition, with nitric acid. PVC (P: 830) was heated at a rate of 2° C/min in the ranges from 80° C to 300, 350, 400 and 450° C in a stream of air. The resulting char was found to have carbonyl groups, other oxygenated groups and aromatic structures in terms of IR spectroscopy. The yield of the char war 28.6-40.2% and the oxygen content of the char was 4.0-10.1%. The atomic ratio of hydrogen to carbon in the char decreased from 0.99 to 0.62 with rising temperature of thermal decomposition.
It was pointed out that lactone and/or ester linkages were formed in the char obtained at 450° C.
Humic acid was obtained in 82.4 and 90.5% yields from the char prepared at 300 and 350° C, respectively, by oxidation with 3 N nitric acid at 100° C for 5 hr. From the Char pr!pared at 400 and 450° C, humic acid was obtained in 93.6% yield by oxidation with 5 N nitric acid. The humic acid has similar properties to those of the regenerated humic acid obtained from coal by oxidation with nitric acid.
The humic acid has good adsorptive ability for heavy mdalic ions. By shaking 100 ml of 2x10' molf/ CdCl2 aqueous solution containing 0.1 g of the humic acid for 5 hr, 84.0-96.5% of Cizl ion was adsorbed on the humic acid.
The structure of the char from PVC and the properties of the humic acid were also discussed.