An Experimental Study of Crystallization of Oxalic Acid Dihydrate (C2H2O42H2O) Using the Seeding Technique

Crystallization is one of the prominent unit operation processes in major chemical industries, such as pharmaceuticals, food, fine chemicals, etc. It is the last stage in the entire chemical process, and it is the purification step to separate one component from a multicomponent mixture using different crystallization methods. The objective of the crystallization process is to achieve good crystal attributes, such as good crystal purity, good crystal size distribution, mean crystal size, morphology, size, etc. The crystal quality can be achieved through various techniques that include the seeding technique and the non-seeding technique. The former is considered important when the objective of the product quality is not met with the usual crystallization process. It can direct towards process optimization. Although, it is a meaningful approach, it is a challenging task to achieve the desired quality of the crystal, process efficiency and optimization of the overall crystallization process. Seeding can also be done at a low level of supersaturation to trigger secondary nucleation, which is an important part of the crystallization process in crystal development. The solute concentration is increased in the existing solution with seeding of similar crystals. Reproducible crystal quality can be achieved by defining the reproducible crystal growth rate at the point of the process where seed crystals are added. The essential surface area of the seeds and the quality of the surface area are also important to define the size of the crystal. However, temperature and concentration play an important role in achieving the desired crystal attributes. The type of the temperature profile applied has a significant role in achieving the final crystalline product in the batch crystallization process. This experimental study aims to understand the particle size distribution of oxalic acid dihydrate (C 2 H 2 O 4 2H 2 O) crystals by evaluating solubility of oxalic acid at three different temperatures using seed crystals of size 250 µm.