Preparation of adsorptive nanoporous membrane using powder activated carbon: Isotherm and thermodynamic studies

Adsorptive polyethesulfone(PES)membranes were prepared by intercalation of powder activated carbon(PAC)with and without functionalization.Accordingly,PAC was aminated with 1,5-diamino-2-methylpentane,and the physicochemical properties of the functionalized PAC were analyzed.Intercalation of PAC within the PES scaffold changed the porosity and mean pore size of the aminated membrane(AC-NH2)from 52.6%to 92.5%and from 22.6 nm to 3.5 nm,respectively.The effect of temperature on the performance of the modified mem-branes was monitored by the flux and chemical oxygen demand(COD)removal of leachate.At ambient tempera-ture,the COD removal of the neat,AC-containing,and AC-NH2 membranes was 47%,52%,and 58.5%,respec-tively.A similar increment was obtained for the membrane flux,which was due to the synergistic effect of the high porosity and large number of hydrophilic functional groups.The experimental leachate adsorption data were analyzed by Langmuir,Freundlich,and Dubinin-Radushkevich isotherm models.For all membranes,the significant thermodynamic parameters(ΔH,ΔS,and ΔG)were calculated and compared.The isosteric heat of adsorption was lower than 80 kJ·mol^-1,indicating that the interaction between the membranes and the leachate is mainly physical,involving weak van der Waals forces.

Building a Highly Stable Ultrathin Nanoporous Layer Assisted by Glucose for Desalination

Although nanoporous membranes are of great interest in desalination,it is still challenging to construct highly permeable nanoporous membranes with excellent rejections for an efficient desalination process.In this work,highly permeable nanoporous membranes were built from renewable resources,assisted by the versatile functions of glucose and dopamine,with coupling reactive groups via interfacial reaction with 1,3,5-benzenetricarbonyl trichloride(TMC).The small molecules(0.66 nm)of glucose,which have high hydrophilicity,can diffuse into the membrane for an effective reaction to ensure structural integration.Our novel ultrathin(~44 nm)nanofiltration(NF)membrane exhibits ultra-high Na_(2)SO_(4)flux and excellent rejection of Na_(2)SO_(4)(66.5 L·m^(-2)·h^(-1),97.3%)and MgSO4(63.0 L·m^(-2)·h^(-1),92.1%)under a pressure of 5 bar(1 bar=10^(5)Pa)which is much superior to the performance of natural-product NF membranes.The membrane demonstrates excellent long-term stability,as well as tremendous acid-base and alkali-base stability and high anti-pollution capacity.The designed membrane materials and architecture open a new door to biopolymer-based separation membranes beyond existing membrane materials.

Ion separation and water purification by applying external electric field on porous graphene membrane

Using molecular dynamics （MD） simulations, a porous graphene membrane was exposed to external electric fields to separate positive and negative ions from salt-water and to produce fresh water. It was observed that, by increasing the strength of the applied electric field, ion separation improved noticeably. In addition, to obtain fresh water, the designed system included two graphene membranes, which are exposed to two external electric fields in opposite directions. Ion rejection was found to be greater than 93% for the electric field of 10 mV/A and higher. This atomic-level simulation increases the understanding of electric field effects on desalination using multilayer graphene membranes and can be helpful in designing more efficient membranes.

Ultra-low noise measurements of nanopore-based single molecular detection

Nanopore is an ultra-sensitive electrochemical technique for single molecular detection in confined space. To suppress the noise in detection of the weak current of nanopore, we investigated the influence of membrane capacitance and applied voltage on the noise of the current signal by model analysis, simulation and experiment. The obtained results demonstrated that membrane capacitance affects the noise by amplifying the noise of the applied voltage. Therefore, suppression of applied voltage noise is an efficient approach for reducing the noise in nanopore detection. Here, we developed an ultra-low noise instrument system for detecting the single molecule signal in nanopores. As demonstrated by nanopore experiments, the p-p noise of the developed system during the recording is reduced to 3.2B pA using the filter of 5 kHz. Therefore, the developed system could be applied in highly sensitive nanopore detection.