You can engage an EMC partner to perform the disk sanitation activity for you. Otherwise, you'll have to decide which method you wish to use. Unlike the VMAX or newer VNX arrays, the CX-40 does not have a native method to perform a DOD wipe. Depending on your requirements, could simply create a massive LUN, write data to it, then destroy it, but it depends on how stringent you must be for your requirements.
Let us know if that helps!
Read here for EMC Certified Data Erasure Services : http://www.emc.com/collateral/services/consulting/h1321-certified-data-erasure-serv-ss.pdf
For CLARiiON, read here : http://www.emc.com/collateral/hardware/service-overview/h5572-emc-cert-data-erasure-clariion.pdf
You may can find different tools and methods for the same with 3rd party tools through googleing, but if possible use the EMC Certified methods.
Another way is you can do the zeroing for each single disk with the below mentioned naviseccli command,
naviseccli -h <SP IP> zerodisk -messner <ID of drive> start
For checking the status,
naviseccli -h <SP IP> zerodisk -messner <ID of drive> status
Eg: naviseccli -h 10.192.11.221 zerodisk -messner 1_10 start