Competitive adsorption of multicomponent volatile organic compounds on biochar.

Crude oil contaminated lands are recognised to have significant contributions to airborne volatile organic compounds (VOCs) with adverse effects on human health and tropospheric ozone. Soil capping systems for controlling harmful emissions are critical engineering solutions where advanced soil remediation techniques are neither available nor feasible. Studies on the adsorption of single VOC species in biochar have shown promising results as a potential capping material; however, current understanding of mixed gas system and multi-component adsorption of VOCs on biochar which would represent more realistic in situ conditions is very limited. We present, for the first time, the results of a study on competitive adsorption of mixed VOCs, including aromatic and non-aromatic VOCs commonly emitted from crude oil contaminated sites on two types of biochar pyrolysed at 500°C from wheat straw and bagasse as feedstock. The kinetics of sorption of multicomponent VOCs including acetone, hexane, toluene and p-xylene in biochar are studied based on the results of an extensive experimental investigation using a bespoke laboratory setup. Both biochar types used in this study presented a high sorption capacity for VOC compounds when tested individually (51-110 mg/g). For the multicomponent mixture, the competition for occupying sorption sites on biochar surface resulted in a lower absolute sorption capacity for each species, however, the overall sorption capacity of biochar remained more or less similar to that observed in the single gas experiments (50-109 mg/g). The chemical interactions via hydrogen bonds, electrostatic attraction, and pore-filling were found to be the main mechanisms of adsorption of VOC in the biochar studied. The efficiency of biochar regeneration was assessed through five cycles of adsorption-desorption tests and was found to be between 88% and 96%. The incomplete desorption observed confirm the formation of likely permanent bonds and heel build-ups during the sorption process.

Nano-biopolymer effect on forward osmosis performance of cellulosic membrane: High water flux and low reverse salt.

Chitosan nano-biopolymers (CS-NPs) were synthesized, and nanocomposite membranes were prepared via phase inversion method. The synthesized CS-NPs and fabricated membranes were characterized using TEM, SEM, AFM, hydrophilicity analysis and porosity measurement techniques. Surface hydrophilicity and porosity of nanocomposite membranes considerably increased compared with pristine CA membrane, and structural parameter significantly decreased to 0.30-1.3 mm. Nanocomposite membranes presented superior forward osmosis (FO) performance by offering a high water flux and low reverse solute flux compared with CA so that optimum osmotic water flux reached 31.2 LMH, about four times higher than that of unmodified membrane. In this regard, reverse salt flux remarkably reduced from 2.33 gMH for pristine membrane to 0.09 gMH for nanocomposite membrane demonstrating efficacy of employed modification method in simultaneous improvement of both water and reverse salt flux. Nanocomposite membrane applicability was also investigated in desalination of seawater proving the satisfactory performance of membranes in FO.

Nontoxic silver nanocluster-induced folding, fibrillation, and aggregation of blood plasma proteins.

In recent years, concerns have been raised considering the potential risks of nanocluster (NC) for the environment and human health. Since the blood circulation system is probably the first entry route of NC into the human body, adsorption of blood proteins on NC may change cellular responses, including cellular uptake efficiency, bio distribution patterns, and nanotoxicity profiles, besides other biological effects. Therefore, the interaction of NCs with proteins and the cellular implications can be therapeutically of great importance. Adsorption of human blood proteins on NCs has been methodically investigated. In the present study, the first analysis of fibrillation was conducted between MBI-AgNCs and human serum (a complex biofluid). AgNCs were prepared by coating with 2-mercaptobenzimidazole. Then, interactions with human blood proteins, such as immunoglobulin, albumin, and insulin were investigated using various experimental approaches. Upon protein association, the fluorescence of proteins significantly decreased, accompanied by a blue shift in the AgNCs-human serum albumin (HSA) system and a red shift in the AgNCs-insulin/γ-globulin. Concomitantly, circular dichroism spectroscopy and atomic force microscopy were employed to investigate the effects of protein binding to NCs. We found that AgNCs induced γ-globulin aggregation. HSA at the AgNC surface was partially unfolded and could promote protein self-assembly into amyloid fibrils, while the surface morphology remained unchanged after insulin incubation. The atomic force microscopy (AFM) data and the ThT and CR analysis of the proteins, as well as circular dichroism (CD) and fluorescence findings, support the use of AgNCs as an indicator for monitoring the progress of HSA fibrillogenesis. Additionally, cytotoxicity assays were used to ensure the biocompatibility of nanoparticles within the applicable limits.

Nano-porous SAPO-34 enhanced thin-film nanocomposite polymeric membrane: Simultaneously high water permeation and complete removal of cationic/anionic dyes from water.

Thin-film nanocomposite (TFN) membranes were prepared by embedding nano-porous SAPO-34 nanoparticles in a polypyrrole thin-film layer polymerized on PES substrate. SEM, EDX, AFM, hydrophilicity, zeta potential and MWCO measurements were applied to verify characteristics of membranes. TFN membranes presented considerably higher pure water permeability (by more than 300%) due to high hydrophilicity and also nano-channels created in thin-film. Performance of TFN membranes were also evaluated by removal of different anionic and cationic dyes (methyl violet 6B, reactive blue 4 and acid blue 193) from water. TFN membranes effectively removed 100% of all dyes from feed aqueous solutions with a low concentration (50 mg/l). Moreover, TFN membrane prepared with the highest amount of nano-filler presented an elevated water flux in filtration of solutions containing each dyes (e.g. more than 500% for reactive blue 4), a reduced flux decline ratio (36%) and also a higher flux recovery ratio (85%) in comparison with the pristine thin-film membrane, consequently indicating high performance of TFN membranes and potential of recovery just after a simple water washing. TFN membranes also revealed an efficient performance in filtration of high concentrations of dye solutions as well as in treatment of a real wastewater produced by a weaving company.

Polyethersulfone nanofiltration membrane embedded by chitosan nanoparticles: Fabrication, characterization and performance in nitrate removal from water.

In this research, chitosan nanobiopolymers (CS-NPs) were synthesized using tripoly phosphate and transferred into the organic solvent via solvent exchange method. Different amounts of chitosan nanopolymers were embedded into the polyethersulfone (PES) membrane prepared by phase inversion precipitation method. The membranes were employed for nitrate removal from water under various solution pHs (4.5, 7.0 and 9.0). Scanning electron microscopy, atomic force microscopy, porosity, water contact angle and pure water flux measurements were employed to characterize the fabricated membranes. Addition of chitosan nanoparticles into the membrane matrix increased the water permeability from 13 for pristine membrane to 22 kg/m2 h for modified membrane with 0.2 wt.% nanopolymer. However, the application of CS-NPs more than 0.4 wt.% led to membranes with a compact matrix and dense structure, thereby reducing water permeation even lower than PES. At all tested solution pHs, nitrate removal efficiency was significantly improved in comparison with pristine PES at as a result of adsorptive properties of chitosan biopolymer. The complete nitrate removal (100%) was achieved at acidic pH due to protonation of amine groups of CS-NPs creating positive charge on the membrane surface.

Novel antifouling nano-enhanced thin-film composite membrane containing cross-linkable acrylate-alumoxane nanoparticles for water softening.

A novel thin-film composite (TFC) nanofiltration membrane was prepared using polymerization of pyrrole monomers on the PES ultrafiltration membrane. To improve the characteristics of hydrophobic polypyrrole (PPy) thin-film layer, cross-linkable acrylate-functionalized alumoxane nanoparticles with different concentrations were embedded into the thin-film during polymerization process, and thin-film nanocomposite (TFNC) membranes were prepared. The characteristics and performance of TFC and TFNC membranes were assessed through the morphological analyses (SEM, AFM), measurement of hydrophilicity and solid-liquid interfacial free energy, water permeability and Mg2+ removal tests. Addition of proper amount of nanoparticles into the polymerization mixture led to the preparation of membranes with more hydrophilic, thinner and smoother active layer as well as higher water permeability compared to TFC control membrane. TFNC membrane prepared with 0.025g of nanoparticles was the most efficient membrane since it exhibited the highest rejection of MgCl2 and MgSO4 salts. Antifouling capability of membranes, in terms of flux recovery and fouling parameters, demonstrated the high tolerance of TFNC against fouling.

PES mixed matrix nanofiltration membrane embedded with polymer wrapped MWCNT: Fabrication and performance optimization in dye removal by RSM.

MWCNTs were wrapped by poly(sodium 4-styrenesulfonate) (PSS), and different amounts of raw and polymer wrapped MWCNTs were implemented to fabricate PES mixed matrix membranes by phase inversion method. Success of wrapping was probed by FTIR spectroscopy, and prepared membranes were characterized by SEM, AFM, porosity, and water contact angle measurements. Response surface methodology (RSM) was employed to optimize the permeate flux and dye removal efficiency of membranes with three variables of concentration, pH of dye solution, and membrane composition. A response surface (RS) with a D-optimal design was defined to build the mathematical model, minimize the number of experiments, and investigate the effect of parameters on the response. Adequacy of the obtained model was confirmed by means of variance analysis and additional experiments. Based on observed and predicted results, wrapping CNTs by PSS improved permeation flux and dye removal efficiency of MMMs. Validity of model was verified according to the good agreement between predicted and experimental results. Membrane mixed with 0.1 wt.% polymer wrapped MWCNTs offered the highest permeation flux as well as dye removal efficiency. According to the model response, in order to achieve a higher dye removal, an acidic pH and a moderate dye solution concentration are recommended. Additionally, basic solution pH (9.0) and a dilute dye solution are suggested to reach a higher permeation flux.