Why MgCl2 is a better coagulant than Kcl for AS2S3 sol?

The salt As2S3 is a negatively charged salt. According to Hardy and Schulz rule, the ions having higher positive charge value will attract more negative charged ions. Here, Mg2+ has 2 positive ions where K+ has 1 positive ion. As the charge of Mg2+ is more, it'll attract more negative charged ions; so gravitational force will work downward and will easily settle down than K+. That's why MgCl2 is a better coagulant than KCl.