Preparation of three kinds of efficient sludge-derived adsorbents for metal ions and organic wastewater purification

The sludge is pretreated to prepare the sludge bicohar by pyrolysis, which is divided into high-carbon sludge biochar and high-ash sludge biochar using flotation. The high-carbon sludge biochar and high-ash sludge biochar are used to prepare the sludge activated carbon, MgAl-layered double hydroxides (MgAl-LDO) and sludge ceramsite for Pb2+, methyl orange (MO) and ciprofloxacin (CIP) removal from wastewater, respectively. The sludge activated carbon is prepared from high-carbon sludge biochar using ZnCl2 as chemical agent in the additive of pine sawdust for MO and CIP removal with adsorption amount of the 754.05 mg/g and 635.62 mg/g, respectively. Mg-Al LDO is prepared from the leaching solution of the high-ash sludge bicohar, which can quickly remove Pb2+ from wastewater with adsorption amount of 147.89 mg/g. Mg-Al LDO has good reusability after three cycles. The MO/CIP and Pb2+ adsorption mechanism are analyzed and investigated. The sludge ceramsite prepared from the leaching residue of high-ash sludge bicohar is also used for Pb2+ removal with adsorption capacity of the 1.44 mg/g. The above results indicate that sludge is converted into three kinds of the adsorbents for pollution removal from wastewater, realizing the high value utilization of sludge.