A NEW TECHNICS ON REMOVAL OF HEAVY METALS FROM SEWAGE SLUDGE WITH CITRIC ACID

A new technique on removal of the heavy metals from sludge has been brought forward, which consists of three steps: extraction, separation of solids and liquid, cleaning and recycling of extracting liquid. The main factors on the third step have been studied. The following results have been received: 732# action resin has excellent capacity, whose ion exchange rate for heavy metals reaches almost 100%. The regeneration rate of Cu, Zn and Ni respectively reaches 88.85%, 86.15% and 88.40% with 5% HCl by dynamic counter flow operation. Replacement rate of most heavy metals can be reached above 90% with Aluminum piece. Recycling experiment proves that not only the content of heavy metals in the sewage sludge after treatment accords with standard, but also the citric acid can be recycled.