HNO3 can be used as an oxidizing agent to modify acidic functional
groups on the surface of B–SBA–K in order to enhance its
adsorption capacity to Pb2+. Therefore, B–SBA–K was soaked in
60% HNO3 and heated for 6 h at 90 C in a water bath, and finally the adsorbent Acid-B–SBA–K was obtained.