Solvent Removal Methods

Once the solute is extracted into the extraction solvent, it generally must be isolated from the solvent. Thus, the chosen solvent should facilitate this procedure. Most simply, this is done by evaporation or distillation of the solvent from the solute. Distillation procedures can be quite efficient. Other solvent removal methods include precipitation, adsorption, and back-extraction. Precipitation of the solute and subsequent decanting or filtering usually results in low yields. Where appropriate, these yields can be moderately improved by converting the (ionic) solute to the salt. Adsorption onto a suitable stationary phase is especially desirable if additional solute purification is needed. Back-extraction also results in additional purification. This secondary extraction can use a third solvent or can be an extraction back into the original feed solvent (for liquid systems) through changes in the distribution ratio by adjusting parameters such as pH. For example, with ionizable compounds and an aqueous phase the fraction ionized into the aqueous phase is approximated by the Henderson-Hasselbach equation (i.e., log ionized (a)/log nonionized (1 — a) = pH — pKa). So in this example, the ionic form of 99% of the solute can be changed by adjusting the pH by two units from the pK„.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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