According to Official Guinness Records,
The most steel cans collected in one month is 2,656,284, weighing 82,929 kg (182,827 lb 2 oz) and was achieved by Collect-a-Can (South Africa) in South Africa, between 1-31 October 2010.
Collect-a-Can first attempted this record in 2007, and has broken their own records twice since. Collections occurred at schools across the country for the month of October to promote the recylcing of cans in South Africa.
For a complete list of 2010 records, please visit 2010 Guinness Records in South Africa.