Replace "" don't work using replace

I use code to remove "" in datatable (dt) as below but don't work.
How to fix it? Need to add another code to update?
For i = 0 To dt.Rows.Count - 1
For j As Integer = 0 To dt.Columns.Count - 1
dt.Rows(i).Item(j).ToString.Replace("""", " ")
Next
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