A wheat and hemp lignin, obtained from a soda pulping-precipitation process, was carbonized at 800 ◦C
under N2 atmosphere. The resulting carbon material was thermally activated under oxidative atmosphere
at four different temperatures (150, 200, 300 and 350 ◦C). The materials prepared at higher activation
temperatures (300 and 350 ◦C) have proven their potential in the elimination of 4-nitrophenol (4-NP)
from aqueous model solutions (5 g L−1) when using catalytic wet peroxide oxidation (CWPO). In these
conditions we were able to remove around 70% of 4-NP after 24 h, with an efficient H2O2 decomposition,
in experiments conducted at relatively mild operating conditions (atmospheric pressure, 50 ◦C, pH = 3,
catalyst load = 2.5 g L−1 and [H2O2]0 = 17.8 g L−1). By increasing the working temperature to 80 ◦C, complete
4-NP removal was obtained within 48 h (against 93% 4-NP removal at 50 ◦C), with an efficiency
of H2O2 consumption of 70% and a significant mineralization (61%). On the other hand, the materials
prepared at lower activation temperatures (150 and 200 ◦C), with higher basicity, promote the faster but
inefficient H2O2 decomposition, 4-NP removal being lower than 25% after 24 h at 50 ◦C in CWPO. This
can be attributed to the formation of species other than HO• radicals during H2O2 decomposition, the
recombination of the formed radicals into non-reactive species and a poor adsorption capacity.
This work was financially supported by Project POCI-01-0145-FEDER-006984–Associate Laboratory LSRE-LCM, funded by FEDER through COMPETE2020 − Programa Operacional Competitividade e Internacionalização (POCI) − and by national funds through FCT − Fundação para a Ciência e a Tecnologia, and Project AIProcMat@N2020 − Advanced Industrial Processes and Mate-rials for a Sustainable Northern Region of Portugal 2020, withthe reference NORTE-01-0145-FEDER-000006, supported by Norte Portugal Regional Operational Programme (NORTE 2020), underthe Portugal 2020 Partnership Agreement, through the European Regional Development Fund (FEDER). M. Martin Martinez and A.M.T. Silva acknowledge respectively financial support from the FCT Postdoctoral grant SFRH/BPD/108510/2015 and the FCT Inves-tigator 2013 ProgrammeIF/01501/2013 with financing from theEuropean Social Fund and the Human Potential Operational Programme.
