2 research outputs found
Catalytic Removal of Aqueous Contaminants on N‑Doped Graphitic Biochars: Inherent Roles of Adsorption and Nonradical Mechanisms
Environmentally
friendly and low-cost catalysts are important for
the rapid mineralization of organic contaminants in powerful advanced
oxidation processes (AOPs). In this study, we reported N-doped graphitic
biochars (N-BCs) as low-cost and efficient catalysts for peroxydisulfate
(PDS) activation and the degradation of diverse organic pollutants
in water treatment, including Orange G, phenol, sulfamethoxazole,
and bisphenol A. The biochars at high annealing temperatures (>700
°C) presented highly graphitic nanosheets, large specific surface
areas (SSAs), and rich doped nitrogen. In particular, N-BC derived
at 900 °C (N-BC900) exhibited the highest degradation rate, which
was 39-fold and 6.5-fold of that on N-BC400 and pristine biochar,
respectively, and the N-BC900 surpassed most popular metal or nanocarbon
catalysts. Different from the radical-based oxidation in N-BC400/PDS
via the persistent free radicals (PFRs), singlet oxygen and nonradical
pathways (surface-confined activated persulfate–carbon complexes)
were discovered to dominate the oxidation processes in N-BC900/PDS.
Moreover, the adsorption of organics was determined to be the key
step determining reaction rate, revealing that the pre-adsorption
of reactants significantly accelerated the nonradical oxidation pathway.
This study not only provides robust and cheap carbonaceous materials
for environmental remediation but also enables the first insight into
the graphitic biochar-based nonradical catalysis
Magnetic Nanoscale Zerovalent Iron Assisted Biochar: Interfacial Chemical Behaviors and Heavy Metals Remediation Performance
It has been reported
that zerovalent iron can help biochar improve
efficiency in heavy metal (HM) absorption, but the surface chemical
behaviors and HM removal mechanisms remain unclear. We successfully
synthesized the magnetic nanoscale zerovalent iron assisted biochar
(nZVI-BC). The porosity, crystal structure, surface carbon/iron atom
state, and element distribution were comprehensively investigated
to understand nZVI-BC’s interfacial chemical behaviors and
HM removal mechanisms. We clearly revealed the formation of a nanoscale
Fe<sup>0</sup> core–Fe<sub>3</sub>O<sub>4</sub> shell on the
surface/pores/channels of biochar. With the combination of iron nanoparticles
and biochar, C–O/COOH groups were cracked with the formation
of CO/CC, indicating the C–O–Fe acted
as an electron acceptor during the reduction reaction. We also demonstrated
that the stabilization was dramatically improved in the nZVI-BC, while
more reduced iron and better homogeneity were observed. These results,
showing the surface chemical behaviors of nZVI-BC, would help increase
our understanding of the HM removal mechanisms. Moreover, our demonstration
of the superior removal ability of multiple HM (Pb<sup>2+</sup>, Cd<sup>2+</sup>, Cr<sup>6+</sup>, Cu<sup>2+</sup>, Ni<sup>2+</sup>, Zn<sup>2+</sup>) from a solution can provide a breakthrough in making a
feasible material for removing HM from polluted water resources