Halloysite nanotube@carbon with rich carboxyl groups as a multifunctional adsorbent for the efficient removal of cationic Pb( ii ), anionic Cr( vi ) and methylene blue (MB)

A multifunctional halloysite@carbon with rich carboxyl group (HNT@CRC) is prepared using a facile and green method, and the adsorbent exhibits excellent adsorption performance towards pollutants with different features like Pb( ii ), Cr( vi ) and methylene blue (MB).