Efficient adsorption of methylene blue on carboxylate-rich hydrochar prepared by one-step hydrothermal carbonization of bamboo and acrylic acid with ammonium persulphate.

Hydrochar (AAHC) with rich carboxylate groups was prepared by one-step hydrothermal carbonization (HTC) of bamboo and acrylic acid with the presence of ammonium persulphate, and then activated by a sodium hydroxide solution. AAHC was featured by elemental analysis, SEM, XPS, FTIR, Zeta potential analysis and N2 adsorption-desorption isotherms, and applied to test adsorptive ability of methylene blue (MB) by batch sorption experiments. Despite a small Brunauer-Emmett-Teller (BET) surface area of 5.03 m2·g-1, AAHC has excellent MB adsorbing capacity owing to the richness of carboxylate groups. Compared with hydrochar produced without adding ammonium persulphate, AAHC exhibits larger BET surface, pore volume and carboxylate groups, indicating a small amount of ammonium persulfate plays an important role in HTC in addition to the free radical initiator. This work provides a facile and cheap method combining HTC and polymerization for preparation of carboxylate-rich hydrochar.

High effective adsorption of Pb(II) from solution by biochar derived from torrefaction of ammonium persulphate pretreated bamboo.

Biochar was prepared by torrefaction of ammonium persulphate pretreated bamboo (labeled as APBC) and applied into elimination of Pb(II) from water solutions. APBC was characterized by N2 adsorption-desorption isotherms, elemental and Zeta potential analyses, SEM-EDS, XPS, and FTIR. Abundant N- and O-containing groups appeared atop APBC. Batch sorption assays revealed that APBC had high affinity and strong sorption ability towards Pb(II). The high Pb(II) adsorbing ability was attributed to the high contents of N- and O-containing functional groups of APBC. The adsorption mechanism mainly occurred by inner-sphere surface complexation. Hence, torrefaction of ammonium persulphate pretreated bamboo is a promising strategy for producing efficient biochar that is applicable for industrial wastewater treatment.