Methyl-Cyclohexane Methanol (MCHM) Isomer-Dependent Binding on Amorphous Carbon Surfaces

In January 2014, over 10,000 gallons of methyl-cyclohexane methanol (MCHM) leaked into the Elk River in West Virginia, in a chemical spill incident that contaminated a large portion of the state’s water supply and left over 300,000 residents without clean water for many days and weeks. Initial efforts to remove MCHM at the treatment plant centered on the use of granulated activated carbon (GAC), which removed some of the chemical from the water, but MCHM levels were not lowered to a “non-detect” status until well after the chemical plume had moved downstream of the intake. Months later, MCHM was again detected at the outflow (but not the inflow) at the water treatment facility, necessitating the full and costly replacement of all GAC in the facility. The purpose of this study is to investigate the hypothesis that preferential absorbance of one of the two MCHM isomers, coupled with seasonal variations in water temperature, explain this contrary observation. Calculated intermolecular potentials between ovalene (a large planar polycyclic aromatic hydrocarbon) and the MCHM isomers were compared to physisorption potentials of MCHM onto an amorphous carbon model. While a molecular mechanics (MM) force field predicts no difference in the average interaction potentials between the cis- and trans-MCHM with the planar ovalene structure, MM predicts that the trans isomer binds stronger than the cis isomer to the amorphous carbon surface. Semi-empirical and density functional theory also predict stronger binding of trans-MCHM on both the planar and amorphous surfaces. The differences in the isomer binding strengths on amorphous carbon imply preferential absorbance of the trans isomer onto activated charcoal filter media. Considering seasonal water temperatures, simple Arrhenius kinetics arguments based on these predicted binding energies help explain the environmental observations of MCHM leeching from the GAC filters months after the spill. Overall, this work shows the important implications that can arise from detailed interfacial chemistry investigations.

The crystal structure of aqua{N,N,N′,N′-tetrakis[(1H-benzimidazol-κN3) methyl]cyclohexane-1,2-diamine}lead(II) diacetate–methanol (1/2), C44H54N10O7Pb

PbC44H54N10O7, triclinic, P1̄ (no. 2), a = 12.096(2) Å, b = 12.916(2) Å, c = 16.5904(7) Å, α = 101.163(2)°, β = 110.634(2)°, γ = 100.698(2)°, V = 2287.0(4) Å3, Z = 2, Rgt(F) = 0.0604, wRref(F2) = 0.1409, T = 298(2) K.

Using Chou’s 5-Step Rule to Evaluate the Stability of Tautomers: Susceptibility of 2-[(Phenylimino)-methyl]-cyclohexane-1,3-diones to Tautomerization Based on the Calculated Gibbs Free Energies

Gibbs free energies, based on DFT (Density Functional Theory) calculations, prove that enaminone (2-(anilinemethylidene)cyclohexane-1,3-dione) and ketamine (2-[(phenylimino)-methyl]cyclohexane-1,3-dione) are the most and least stable tautomeric forms of the studied systems, respectively. 1H and 13C NMR spectra prove that 2-(anilinemethylidene)cyclohexane-1,3-diones are the only tautomeric species present in dimethylsulfoxide solution (a very weak signal can be seen only for the p-methoxy derivatives). The zwitterionic character of these enaminones is strengthened by naphthoannulation and by the insertion of the electron-withdrawing substituent into the benzene ring (the latter weakens the intramolecular hydrogen bond in the compound). Substituent and naphtoannulation have no effect on the stability of the studied tautomers. Slight twisting of the benzene ring, with respect to the CArNC plane (seen in the crystalline state), was proven to also take place in vacuum and in solution.

PYROLYSIS OF CASSAVA BAGASSE INTO BIO-OIL USING Ni/NZA CATALYSTS

Cassava bagasse is a solid tapioca industry waste that can be used as an energy source. In this study, cassava bagasse was pyrolyzed to produce bio-oil and studied the effect of Ni/NZA catalysts on yield, heating value and distribution of bio-oil products. The making of Ni/NZA catalyst starts with the process of activating natural zeolite to produce natural zeolite activated (NZA). Furthermore, impregnation of Ni metals in NZA with Ni levels 1, 2 and 3% w/w (Ni/NZA). The next step is calcination, oxidation and reduction. Cassava is peeled, shredded, washed, filtered and dried and then mashed and screened with a 60 and 80 mesh sieve to obtain cassava bagasse biomass with a size of -60+80 mesh. 50 grams of cassava bagasse with 500 ml silinap and 1.5 gram Ni/NZA catalyst are pyrolyzed at 320oC with nitrogen gas flow of 80 mL/min. Bio-oil products are analyzed by the heating value and distribution of the products. The yield of bio-oil obtained on pyrolysis using 0% Ni/NZA was 54.27% and pyrolysis using 2% Ni/NZA obtained the highest yield of 61.87%. The highest bio-oil heating value was obtained in pyrolysis using 0% Ni/NZA which is 46.78 MJ/kg and lower with increasing Ni levels in NZA. The results of GC-MS analysis of the bio-oil products showed that the use of 1% Ni/NZA catalyst significantly increased the percent area of several components i.e. 2,4,4-trimethy-l-1-Pentene, 2,5-dimethyl-2,4-Hexadiene, and 2,4,4-trimethyl-2-Pentene and decreases the percent area of some other components i.e. 1-bromo-3-methyl-Cyclohexane, 2-methyl-1-Propene,tetramer, 1-(1,1-dimethylethoxy)-3-methyl-Cyclohexene and 3-(3,3-dimethylbutyl)-Cyclohexanone.