What is the definition of "absorbent" in absorption method in gas analysis? ?

A liquid that can selectively dissolve certain specific components in the mixed gas in the absorption operation. The absorbent can be pure liquid or solution. Generally divided into physical absorbent and chemical absorbent. There is no chemical reaction between physical absorbent and solute, and the solubility of gas is only related to the law of gas-liquid equilibrium (see vapor-liquid equilibrium); There is a chemical reaction between chemical absorbent and solute, and the solubility of gas is not only related to the law of gas-liquid equilibrium, but also to the law of chemical equilibrium. Most chemical absorbents are solutions of active ingredients, such as potassium carbonate or sodium hydroxide.

When absorption is to prepare solution products, only specific absorbent, such as hydrochloric acid made of hydrogen chloride, can be used, and only water can be used as absorbent. When absorption is the component of separating gas mixture, the reasonable selection of absorbent has great influence on the success of absorption operation. The properties of excellent absorbent include: ① the solubility of solute in it is high, so the process driving force is large, which can reduce the dosage of absorbent; (2) easy to regenerate and recycle; (3) high selectivity, thereby obtaining high-purity desorption gas; (4) Not volatile, so as to reduce losses; ⑤ Low viscosity, difficult foaming, and good contact between two phases in the tower; ⑥ Stable chemical properties, avoiding degradation and deterioration during use; ⑦ Cheap and easily available, safe to use (non-toxic, non-flammable, etc.). ). Generally speaking, chemical absorbents are easy to achieve high selectivity and can make solutes easy to dissolve; But regeneration is more difficult and consumes more energy. In fact, it is difficult to find an ideal absorbent that can meet the above requirements. We can only make a choice according to economic rationality through comprehensive evaluation of existing absorbents. Therefore, the development of new adsorbents with excellent performance has always been concerned by people.