Remove TDE from table columns and uninstall TDE option from DB

Oracle DB:

10.2.0.4

OS:	Red Hat Linux 5.6

Table:

86 Partition - Daily on date

Table size:	450 gb (indexes 120 GB - Not on TDE column
TDE column 1:	DATA1                    VARCHAR2(20 BYTE) ENCRYPT USING 'AES192' NO SALT,
TDE column 2:	PATIENT_NAME    VARCHAR2(25 BYTE) ENCRYPT USING 'AES192' NO SALT,

1. What is the best way to remove TDE from these two columns in this table?

2. Can we use table while we remove the TDE from the table?

3. how to uninstall TDE option from the database?

Thanks.