Dye Removal and Mechanism by Cellulose Fiber-supported Metal Phthalocyanine Derivatives
|School||Zhejiang University of Technology|
|Keywords||Cellulose fibers Matal phthalocyanine Hydrogen peroxide Visible light Mechanism Dyeing auxiliaries|
Water shortage is one of the biggest issues facing society today, the industrial wastewatertreatment has already got to the top priority of environmental field. Recently, the elimination ofhighly toxic and recalcitrant persistent organic pollutants (POPs, such as conjugated dyes,chlorinated aromatic compounds, polybrominated diphenyl ethers, endocrine disruptingchemicals, antibiotics, etc.) at a relatively low concentration has become the concern of theinternational frontier research. Especially in the presence of massive organic and inorganicsubstances, the preferential removal of low-concentration target POPs by conventional AOPstechniques, including some homogeneous and heterogeneous catalytic systems，is extremelydifficult. Therefore, there is an urgent need to design highly efficient catalytic materials for theselective removal of low-concentration POPs from actual wastewater.Cellulose is an organic compound consisting of a linear chain of several hundred to over tenthousand β(1→4) linked D-glucose units, which is the most abundant organic polymer on earth.As a common cellulose derivative, cellulose fibers (CFs) have many inherent outstandingproperties, such as their excellent hydrophilicity, intermolecular hydrogen bondings tructuresand controllable surface charge (zeta potential), which allowed them to be promising supports fora range of catalysts. Metal phthalocyanine derivatives, a macrocyclic conjugate structure with18π electron with stable chemical properties and accessible modification, have attractedconsiderable attention in catalytic field. Phthalocyanine derivatives with different central metalscan be used to propare various phthalocyanine catalytic systems, leading to the commonutilization of phthalocyanine catalysts.Two kinds of cellulose fibers-supported metal phthalocyanine catalysts (Co-TDTAPc-F,Zn-TDTAPc-F) were prepared by covalent grafting method and their load degree and crosssection morphology were then characterized. The results showed that metal phthalocyanine hadbeen already loaded on and into the fiber matrix successfully. The activity of Co-TDTAPc-F onorganic pollutants removal in the presence of H2O2was investigated using a common anion dyeAcid Red G (AR1) as the substrate. Co-TDTAPc-F/H2O2exhibited excellent ability on dyeremoval with good regeneration performance and the effects factors including pH, temperature, oxidant concentration and dyeing auxiliaries were discussed. Hydroxyl radical (HO) was provedto be the dominated reactive species according to EPR analysis. The visible-light photoactivity ofZn-TDTAPc-F toward aqueous basic green1(BG1) degradation has been investigated, whereoxygen was employed as the primary oxidant to generate1O2species. Zn-TDTAPc-F hasexhibited its high efficiency in the organic dyes removal with a good recycle performance, theeffects of photocatalytic oxidation including pH, O2dose, as well as the dyeing auxiliaries werethen be evaluated. The reaction intermidiates and the pathway were discussed in according toUPLC-MS/GC-MS analysis, suggesting the organic molecules were oxidized into biodegradablealiphatic acids and aliphatic alcohols, thus the reaction can be considered as a green catalyticprocess.Furthermore, both the Co-TDTAPc-F and Zn-TDTAPc-F exhibited high efficiency inorganic removal in the presence of various dyeing auxiliaries, which was totally different fromsome conventional catalytic reactions. The positive effects of typical dyeing auxiliaries (NaCl,urea and alcohol compound) were studied followed by the specifically discussion of theinteraction between CFs and the additives, which revealed the pivotal role cellulosic carriersplayed on the wastewater treatment. In the presence of fibers matrix, the catalysts exhititedhigher efficiency than the homogeneous phthalocyanine derivatives mainly by concentratingdyes and catalytic active sites within a catalytic micro-environment provided by the cellulosesupport. More importantly, by taking advantages on the controllable zeta potential andoutstanding swelling properties, the CFs successfully eliminated the inhibitory should have beenin the presence of Cl-and hydroxyl group-containing compound, further enhanced the reaction.Consequently, these findings provide a new approach for removing highly hazardous targetpollutants with a relatively low concentration in actual wastewater with massive organic andinorganic substances, with a full understanding of the interactions among CFs, organic dyes andthe additives, the study reveals the pivotal role of cellulose support in cooperative catalysis andfurther set a good example for the design and optimization of the catalyst via well controlling thesupports.