Comparison of hydrochloric acid and phosphoric acid activated clays

Abstract

To determine if a calcium phosphate has been formed, x-ray diffraction traces were taken of the appropriate samples. To determine if there is calcium phosphate forming on the layers of the clay, the trace of the phosphoric acid washed clays was compared to the analogous hydrochloric acid washed clay. The infrared spectrum was also taken of all samples to aid in this determination. When Inspecting the data, there were noticeable shifts in both the x-ray diffraction traces and the infrared spectra peaks between the sample that had been washed with hydrochloric acid and titrated with calcium hydroxide and the analogous clay sample that had been washed with the phosphoric acid and titrated with calcium hydroxide. These shifts are not indicative of the formation of the hypothesized calcium phosphate but they do give information about the atomic environment on the clay. In the infrared spectra, the phosphoric acid washes had peaks for the Si-O-metal bond shifted to a higher wavenumber as well as the water peaks. This indicates that they have a higher energy in the phosphoric acid washed clays than in the hydrochloric acid washed clays. The x-ray diffraction traces had values of 2-theta shifted to a higher 2-theta indicating a more compact atomic environment. The compact environment would increase the energy of the bonds and therefore increase the peaks present on the infrared spectra of the samples.

When clays are obtained from the Earth, they are non-catalytic for the oligomerization of RNA monomer species and cannot be used as a catalyst for this reaction. To create catalysts for this reaction from clay minerals, the clay must be treated with a preliminary acid wash and then titrated to a pH of 7. However, this does not guarantee that all the clay samples will be catalytic after treatment. Over 300 clays have been studied and only about 10% of the clays are catalytic; however without this process none of the clays are catalytic. During the treatment of the clays with hydrochloric acid, there is little possibility of the formation of insoluble inorganic salts within the interlayers of the clay. However, the use of an equally prebiotic acid, phosphoric acid, could form calcium phosphate which is of limited solubility. Calcium phosphate can have multiple hydrated forms which are all capable of forming during the treatment of the clays. It is currently unknown which, or if any, calcium phosphates form during the phosphoric acid treatment and reside within or on the surface of the clay. Phosphoric acid washes were applied to Treherne, A bed, C bed, and F bed clays. The acid clays were then titrated to a pH of 7.