Chemical characterization and sorption capacity measurements of degraded newsprint from a landfill

Newsprint samples collected from 12-16 ft (top layer (TNP)), 20-24 ft (middle layer (MNP)), and 32-36 ft (bottom layer (BNP)) below the surface of the Norman Landfill (NLF) were characterized by infrared (IR) spectroscopy, cross-polarization, magic-angle spinning 13C nuclear magnetic resonance (CP-MAS 13C NMR) spectroscopy, and tetramethylammonium hydroxide (TMAH) thermochemolysis gas chromatography/mass spectrometry (GC/MS). The extent of NLF newsprint degradation was evaluated by comparing the chemical composition of NLF newsprint to that of fresh newsprint (FNP) and newsprint degraded in the laboratory under methanogenic conditions (DNP). The O-alkyl/alkyl, cellulose/lignin, and lignin/resin acid ratios showed that BNP was the most degraded, and that all three NLF newsprint samples were more degraded than DNP. 13C NMR and TMAH thermochemolysis data demonstrated selective enrichment of lignin over cellulose, and TMAH thermochemolysis further exhibited selective enrichment of resin acids over lignin. In addition, the crystallinity of cellulose in NLF newsprint samples was significantly lower relative to that of FNP and DNP as shown by 13C NMR spectra. The yield of lignin monomers from TMAH thermochemolysis suggested that hydroxyl groups were removed from the propyl side chain of lignin during the anaerobic decomposition of newsprint in the NLF. Moreover, the vanillyl acid/aldehyde ratio, which successfully describes aerobic lignin degradation, was not a good indicator of the anaerobic degradation of lignin on the basis of the TMAH data. The toluene sorption capacity increased as the degree of newsprint degradation increased or as the O-alkyl/alkyl ratio of newsprint decreased. The results of this study further verified that the sorbent O-alkyl/ alkyl ratio is useful for predicting sorption capacities of natural organic materials for hydrophobic organic contaminants.     

Characterization and quantification of reversible redox sites in humic substances

Cyclic oxidation and reduction reactions using oxygen and palladium with H2, respectively, of dissolved humic and fulvic acids (HA and FA) and model quinone compounds were used to structurally characterize and quantify the electron-carrying capacity (ECC) of reversible redox sites present in humic substances. This technique was used to examine 8 quinone compounds and 14 HA and FA samples and identified 3 redox sites as a function of their stability against the Pd-catalyzed hydrogenolysis process. Six highly aliphatic HA and FA isolated from landfill leachate did not contain redox sites under any conditions; however, the other HA and FA demonstrated reversible redox properties characterized by a combination of three redox sites. On the basis of the model compound results, it is proposed that one site consists of a non-quinone structure (NQ) and the other two sites have quinone structures. The two quinone sites differ in that one group (Q1) has electron-withdrawing groups adjacent to the quinone functional group while the second group (Q2) contains either no substituents near the quinone or has nearby electron-donating groups with additional substitutents hindering hydrogenolysis through steric interactions. The reversible ECC of NQ sites ranged from 25 to 265 microequiv e- transferred/g HA or FA, representing 21-56% of the total ECC of the HA and FA when measured with the mildest reducing method (pH 8.0, pure Pd). Q1 redox sites resistant to hydrogenolysis at pH 8.0 using Pd/Al2O3 accounted for 13-58% of the total ECC and ranged from 40 to 120 microequiv e-/ g HA or FA. The most sensitive O2 reversible redox sites accounted for 8-50% of the total ECC (20-220 microequiv e-/ g HA or FA). These results directly demonstrate that HA and FA are capable of acting as reversible electron-transfer agents using different functional groups, some of which may not be quinones.