Since you want to identify target journals which do not have publication charges, you have two options:
1. Subscription-based journals: These journals are not open access, that is, they will charge a fee from anyone who wishes to read your article. However, the author does not have to pay in this publishing model.
2. Open access journals without article processing charges: There are many open access journals that do not charge a fee from the author. It is best if you can find this type of journal because this will ensure that your paper has a wide outreach.
To find open access journals on phytoremediation, you can go to the Directory of Open Access Journals (DOAJ) and run a keyword search. A search for "phytoremediation" at article level turned out 556 results for me. This means that there are 556 articles on this topic in their database. You will have to look at the journals that these articles are published in (also displayed in the search results) and create a list of target journals for your paper. Once you have a fairly long list, you can go to each of these journals' websites and find out if they have article processing charges. Hopefully, you will find at least a few which have very minimum or no charges.
You can do the same on Google Scholar or other databases to find more journals.