Enhancing the performance of porous rice husk silica through branched polyethyleneimine grafting for phosphate adsorption

Removal of phosphate is necessary to prevent eutrophication and remediate other environmental issues. In this study, branched polyethyleneimine (bPEI) was grafted onto rice husk porous silica (RSi-bPEI) to enhance the selective adsorption of phosphate. The adsorption tests for phosphate were performed at various conditions to assess the effects of pH, dose, initial concentration, and contact time. As confirmed by FTIR-spectra, it was proposed that phosphate species anchored onto RSi-bPEI through ion-exchange and hydrogen bonding. The increase in positive charge of RSi-bPEI, which was due to the presence of protonated amine, played a key role in offering more adsorption sites to augment the adsorption by means of electrostatic attraction. Consequently, RSi-bPEI exhibited qm of 123.46 mg g−1, which was two-fold better than that of RSi. The adsorption behavior was best described by Langmuir isotherms and the pseudo-second-order kinetics model. Based on the competitive study, the co-existing anions did not interfere with adsorption due to the fact that phosphate could form both inner and outer sphere complexes. In addition to the high performance, high efficiency in wide pH range as well as good stability and easy recyclability are the other promising criteria of RSi-bPEI that promote its practical usage in treating phosphate-induced eutrophication of water bodies

Facile preparation of palygorskite/chitin nanofibers hybrids nanomaterial with remarkable adsorption capacity

A novel hybrid nanomaterials comprising of palygorskite (PAL) and chitin nanofibers (ChNFs) was successfully synthesized via simple, green and cost effective technology/method and for the first time used in adsorption process. Shrimp sourced chitin is a biopolymer endowed with amino and hydroxyl groups suited for adsorption of metals while PAL is hydrophilic, cheap and eco-friendly material. The hybridization of PAL and ChNFs was achieved under the collision and shear force of ball mill. Morphological analysis showed that ChNFs were attached on PAL leading to enhanced stability of the hybrid dispersion. PAL/ChNFs was used as an adsorbent for Pb(II) ion metal removal. The hybrid adsorbent showed a remarkable adsorption capacity (qe) of 53.7 mg g−1 and removal efficiency of 92.9%. This water dispersible PAL/ChNFs holds great potential in different water treatment related applications that require materials with high hydrophilicity, anti-fouling, biocompatibility, adsorption as well as mechanical properties

Performance of branched polyethyleneimine grafted porous rice husk silica in treating nitrate-rich wastewater via adsorption

Excessive nitrate discharge into aquatic environment is a serious concern as it gives huge impacts on aquatic life as well as corrupts ecosystem and water sources. The effective treatment of nitrate-containing wastewater is essential for the sake of health and environmental protection. In this study, the adsorption of nitrate was carried out using porous rice husk silica functionalized with branched polyethyleneimine (RSi-bPEI). A series of experiments were conducted to measure several adsorption conditions, adsorption isotherms, kinetics, selectivity and reusability. Experimental results demonstrated that the functionalization with branched PEI (bPEI) has significantly improved the adsorption about 40% higher. The ideal conditions for the nitrate adsorption onto RSi-bPEI is at pH = 4, 0.5 g L-1 dose, 50 mg L-1 concentration and about 120 min adsorption time. The pseudo-second-order and Langmuir equations were the most suitable models to describe the nitrate sorption from aqueous solution with high correlation coefficient (0.99). The monolayer adsorption capacity was found to be 94.49 mg g-1 for RSi-bPEI and 47.46 mg g-1 for RSi. The reusability test manifested RSi-bPEI has good regeneration capacity, hence can be an ideal adsorbent for practical wastewater treatment

Flux enhancement in reverse osmosis membranes induced by synergistic effect of incorporated palygorskite/chitin hybrid nanomaterial

The substrate of RO thin film composite membranes offers support for rejection layer formation. It remarkably affects the physicochemical and structural properties of the developed rejection layer. This denotes the relevance of substrates modification in realizing optimized substrate structure in terms of porosity, thickness and tortuosity with the goal of obtaining highly selective and enhanced hydrophilic membrane. Polyamide thin film nanocomposite (TFN) membranes with its polysulfone (PSF) substrate embedded with palygorskite-chitin (PAL-CH) hybrid nanomaterial have been fabricated in this study. The hybridization of palygorskite and chitin nanofibers was performed under the collision as well as the shear force of ball mill. The TFN membranes with different loadings of PAL-CH in the PSF layer were characterized and applied for desalination process. The incorporation of PAL-CH hybrid increased the finger like structure formation and improved the overall hydrophilicity besides highly cross linked and thinner PA layer. The flux of the neat and PAL-CH membranes was 0.82 L m-2h-1and 2.4 L m-2h-1respectively. The developed membranes exhibited remarkably improved pure water flux without compromising the salt rejection. Flux enhancement of 192.7% was achieved using 0.01 wt% PAL-CH3 hybrid nanomaterial

Silver doped titania nanotubes incorporated photocatalytic dual layer antibiofouling hollow fiber membrane for palm oil wastewater treatment

Photocatalytic dual layer hollow fiber membrane (DLHFM) is advantageous over its single layer counterpart due to a better photocatalyst dispersion on the outer layer to maximize the potential of the photocatalyst in improving the overall membrane performance. In this study, a polyvinylidene fluoride (PVDF) dual-layer hollow fiber membrane with antibiofouling properties was successfully synthesized via dry-wet spinning phase inversion method, where the Ag-TNT was incorporated onto the outer layer membrane for photocatalytic degradation of AT-POME pigments in a submerged membrane photoreactor (SMPR). The results revealed that the incorporation of Ag-TNT into the PVDF matrix increased pure water flux from 16.20 L/m2 h for pristine PVDF membrane to 37.12 L/m2 h. The synergistic advantages of photocatalysis and membrane filtration was exhibited by the photocatalytic Ag-TNT membrane which showed the highest AT-POME color removal efficiency of 84.0% compared to the other membranes prepared in this work. With the presence of silver nanoparticles, the modified membrane exhibited antibacterial efficiency of 95.8% with a 1.73 mm inhibition zone around the membrane against P. aeruginosa. Based on the results obtained, the photocatalytic PVDF Ag-TNT membrane showed immense potential as an innovative technology for water reclamation in the palm oil industry

Tailoring the co2-selectivity of interfacial polymerized thin film nanocomposite membrane via the barrier effect of functionalized boron nitride

Membrane-based separation is an appealing solution to mitigate CO2 emission sustainably due to its energy efficiency and environmental friendliness. Attributed to its excellent separation endowed by nanomaterial incorporation, nanocomposite membrane is rigorously developed. This study explored the feasibility of boron nitride (BN) embedment and changes to formation mechanism of ultrathin selective layer of thin film nanocomposite (TFN) are investigated. The effects of amine-functionalization on nanosheet-polymer interaction and CO2 separation performance are also identified. Participation of nanosheets during interfacial polymerization reduced the crosslinking of selective layer, hence, improved TFN permeance while the formation of contorted diffusion paths by the nanosheets favors transport of small gases. Amine-functionalization enhanced the nanosheet-polymer interaction and elevated the membrane affinity towards CO2 which led to enhanced CO2 selectivity. The best TFN prepared in this study exhibited 37% and 20% increment in permeability and selectivity, respectively with respect to neat thin film composite (TFC). It is found that the CO2 separation performance of BN incorporated TFN is on par with many non-porous nanosheet-incorporated TFNs reported in literatures. The transport and barrier effects of BN and functionalized BN are discussed in detail to provide further insights into the development of commercially attractive CO2 selective TFN membranes

Facile preparation of palygorskite/chitin nanofibers hybrids nanomaterial with remarkable adsorption capacity

A novel hybrid nanomaterials comprising of palygorskite (PAL) and chitin nanofibers (ChNFs) was successfully synthesized via simple, green and cost effective technology/method and for the first time used in adsorption process. Shrimp sourced chitin is a biopolymer endowed with amino and hydroxyl groups suited for adsorption of metals while PAL is hydrophilic, cheap and eco-friendly material. The hybridization of PAL and ChNFs was achieved under the collision and shear force of ball mill. Morphological analysis showed that ChNFs were attached on PAL leading to enhanced stability of the hybrid dispersion. PAL/ChNFs was used as an adsorbent for Pb(II) ion metal removal. The hybrid adsorbent showed a remarkable adsorption capacity (qe) of 53.7 mg g−1 and removal efficiency of 92.9%. This water dispersible PAL/ChNFs holds great potential in different water treatment related applications that require materials with high hydrophilicity, anti-fouling, biocompatibility, adsorption as well as mechanical properties

Strategies in forward osmosis membrane substrate fabrication and modification: A review

Forward osmosis (FO) has been recognized as the preferred alternative membrane-based separation technology for conventional water treatment technologies due to its high energy efficiency and promising separation performances. FO has been widely explored in the fields of wastewater treatment, desalination, food industry and bio-products, and energy generation. The substrate of the typically used FO thin film composite membranes serves as a support for selective layer formation and can significantly affect the structural and physicochemical properties of the resultant selective layer. This signifies the importance of substrate exploration to fine-tune proper fabrication and modification in obtaining optimized substrate structure with regards to thickness, tortuosity, and porosity on the two sides. The ultimate goal of substrate modification is to obtain a thin and highly selective membrane with enhanced hydrophilicity, antifouling propensity, as well as long duration stability. This review focuses on the various strategies used for FO membrane substrate fabrication and modification. An overview of FO membranes is first presented. The extant strategies applied in FO membrane substrate fabrications and modifications in addition to efforts made to mitigate membrane fouling are extensively reviewed. Lastly, the future perspective regarding the strategies on different FO substrate layers in water treatment are highlighted