Dual-sim smartphones can be very useful, especially for people who have to divide their time between work and personal life, but they do not want to carry two phones around. However, it appears that this feature can be even more useful and you anticipated.
Many people use WhatsApp for work and they need to separate those conversations from the personal ones as well. If WhatsApp for Business is too much for what you need, or you are not willing to pay for it, you can always use your second sim for another WhatsApp account. While you cannot install WhatsApp twice from the Google Play Store, there are other ways that will allow you to have two different WhatsApp applications on the same phone.
The Parallel Space app
One way to get multiple WhatsApp accounts on the same device is the Parallel Space app. You can use this app in order to clone various applications. This way you can create a second account on the second version of the application. Parallel Space does not work for any application, but luckily for you it does work with WhatsApp.
In order to create two WhatsApp accounts with this application, you will need to download it. You can find it on Play Store, and it won’t take a lot of storage since it only has 6.11 MB. After you have downloaded the app, simply open it and select “Add App” (the plus icon). Look on that list until you find WhatsApp and then select it. After you have selected WhatsApp, open the WhatsApp clone inside the Parallel Space application and register for a new account with your second number. Then you will be able to use WhatsApp with your secondary number as well.