Cellulose Derived Graphenic Fibers for Capacitive Desalination of Brackish Water

Abstract

We describe a simple and inexpensive cellulose-derived and layer-by-layer stacked carbon fiber network electrode for capacitive deionization (CDI) of brackish water. The microstructure and chemical composition were characterized using spectroscopic and microscopic techniques; electrochemical/electrical performance was evaluated by cyclic voltammetry and 4-probe electrical conductivity and surface area by Brunauer-Emmett-Teller analysis, respectively. The desalination performance was investigated using a laboratory batch model CDI unit, under fixed applied voltage and varying salt concentrations. Electro-adsorption of NaCl on the graphite reinforced-cellulose (GrC) electrode reached equilibrium quickly (within 90 min) and the adsorbed salts were released swiftly (in 40 min) back into the solution, during reversal of applied potential. X-ray photoelectron spectroscopic studies clearly illustrate that sodium and chloride ions were physisorbed on the negative and positive electrodes, respectively during electro-adsorption. This GrC electrode showed an electro-adsorption capacity of 13.1 mg/g of the electrode at a cell potential of 1.2 V, with excellent recyclability and complete regeneration. The electrode has a high tendency for removal of specific anions, such as fluoride, nitrate, chloride, and sulfate from water in the following order: Cl->NO3->F->SO4(2-). GrC electrodes also showed resistance to biofouling with negligible biofilm formation even after 5 days of incubation in Pseudomonas putida bacterial culture. Our unique cost-effective methodology of layer-by-layer stacking of carbon nanofibers and concurrent reinforcement using graphite provides uniform conductivity throughout the electrode with fast electro-adsorption, rapid desorption, and extended reuse, making the electrode affordable for capacitive desalination of brackish water.

Influence of various experimental parameters on the capacitive removal of phosphate from aqueous solutions using LDHs/AC composite electrodes

“…The result suggested that the thickness of the EDL was highly correlated with ionic strength. Although the effects of coexisting ions on phosphate adsorption without applied potential followed the order of SO 4 2-> NO 3 -> Cl -, which indicated a great agreement with the conclusion from the study [25], Pugazhenthiran et al [52] implied that the ability of EDL adsorption follows the order of Cl -> NO 3 -> SO 4 2during capacitive deionization. The outer-sphere complexation formed is a dominant action as the adsorption capacity of phosphate decreases with increasing ionic strength [53].…”

Recent advances in carbon fibers derived from biobased precursors

“…Electrospun cellulose‐derived CNFs are promising materials in electrochemical and separation applications . One of the promising applications of cellulose‐based CNFs is anode material for SIB.…”

Challenges and Directions for Green Chemical Engineering—Role of Nanoscale Materials

“…Materials with high electro-adsorption properties have been used to develop capacitive deionization units. 82,83 New technologies using nanostructures have been used to create efficient water harvesters from air. 84 , while new nanocomposite structures with graphene are claimed to be able to reduce desalination costs substantially.…”