Rails - Get Params like "cart_item[price]=5%2C70" out of URL

My View make a redirect an pass the Params

?cart_item[price]=5%2C70€

. I try to get this with

@price = [:cart_item][:price]

, but there i get the error "can't convert Symbol into Integer". I try it with codes like ":cart_item_price" or ":cart_item.price" but always no variable was founded

How can i get this price in my other action ?