Title : Composite materials based on active carbon from biomass residues and zinc oxide nanoparticles for water purification
Recent research concerning heterogeneous catalytic support for chemical synthesis or the development of new chemical compounds is governed lately by two principles: nanoparticle scale materials and sustainable materials. Using biomass residues and processes like pyrolysis and thermal activation or calcinations, we were able, in respect with these principles, to develop new materials for photodegradation processes of organic compounds from wastewaters.
The conversion of biomass residues into value-added products is in line with European directives for environmental protection, which are imposing stringent rules on the implementation of non-polluting organic waste recovery processes. Recent studies involved the fructification of biomass residues into active carbon (CA) in order to obtain composite materials for photocatalytic degradation reactions of organic compounds from contaminated water.
Furthermore, the degradation of organic polluting agents can also be performed successfully in the presence of metal oxides such as ZnO, TiO2, ZrO2, etc, due to their photocatalytic properties, relatively low synthesis costs and non-toxic actions towards environment.
The properties of CA obtained from biomass and used for water purification depend on the nature of biomass, pyrolysis and activation conditions.
Thus, in the first step, our study involved three different types of biomass, such as: algal residues, cherry pits and bacterial cellulose which were pyrolyzed and further activated in different conditions in order to obtain CA.
The recovery of ZnO NPs by sedimentation or filtration could be a difficult task due to the decresed size of the inorganic particles. Thus, the immobilization of such particles on different substrates is necessary in order to better recover and reuse the composite material for a new photodegradation cycle.
For this reason, the next step consisted in the direct generation of ZnO nanoparticles (ZnO NPs) on the surface of CA using both conventional and unconventional reactions (ultrasound-assisted process) to develop composite materials with higher efficiency in the photocatalytic process.
In our case, depending on the ZnO synthesis procedure, the medium size diameter of the inorganic nanoparticles varied from 5 to 30 nm. The CA, ZnO and CA-ZnO composite materials were characterized by FT-IR SEM, EDX, and XRD. The photocatalytic process involved the degradation of methyl orange (MO) under UV light conditions and it was highly influenced by the morphology of the CA-ZnO composite.