Highly effective ultrafiltration membranes based on plastic waste for dye removal from water.

Applicable and low-cost ultrafiltration membranes based on waste polystyrene (WPS) blend and poly vinylidene fluoride (PVDF) were effectively cast on nonwoven support using phase inversion method. Analysis was done into how the WPS ratio affected the morphology and antifouling performance of the fabricated membranes. Cross flow filtration of pure water and various types of polluted aqueous solutions as the feed was used to assess the performance of the membranes. The morphology analysis shows that the WPS/PVDF membrane layer has completely changed from a spongy structure to a finger-like structure. In addition, the modified membrane with 50% WPS demonstrated that the trade-off between selectivity and permeability is met by a significant improvement in the rejection of the membrane with a reduction in permeate flux due to the addition of PVDF. With a water permeability of 50 LMH and 44 LMH, respectively, the optimized WPS-PVDF membrane with 50% WPS could reject 81% and 74% of Congo red dye (CR) and methylene blue dye (MB), respectively. The flux recovery ratio (FRR) reached to 88.2% by increasing PVDF concentration with 50% wt. Also, this membrane has the lowest irreversible fouling (Rir) value of 11.7% and lowest reversible fouling (Rr) value of 27.9%. The percent of cleaning efficiency reach to 71%, 90%, and 85% after eight cycles of humic acid (HA), CR, and MB filtration, respectively, for the modified PS-PVDF (50%-50%). However, higher PVDF values cause the membrane's pores to become clogged, increase the irreversible fouling, and decrease the cleaning efficiency. In addition to providing promising filtration results, the modified membrane is inexpensive because it was made from waste polystyrene, and as a result, it could be scaled up to treat colored wastewater produced by textile industries. PRACTITIONER POINTS: Recycling of plastic waste as an UF membrane for water/wastewater treatment was successfully prepared and investigated. Mechanical properties showed reasonable response with adding PVDF. The modified membrane with 50% PS demonstrated that the trade-off between selectivity and permeability is met by a significant improvement in the rejection.

An immobilized biosorbent from Paenibacillus dendritiformis dead cells and polyethersulfone for the sustainable bioremediation of lead from wastewater.

Heavy metals, including lead, cause serious damage to human health and the surrounding environment. Natural biosorbents arise as environmentally friendly alternatives. In this study, two of the 41 isolates (8EF and 17OS) were the most efficient bacteria for growing on media supplemented with Pb2+ (1000 mg/L). At high concentrations up to 2000 mg/L, the pioneer isolate 17OS exhibited remarkable resistance to multiheavy metals. This isolate was identified as Paenibacillus dendritiformis 17OS and deposited in GenBank under accession number ON705726.1. Design-Expert was used to optimize Pb2+ metal removal by the tested bacteria. Results indicated that four of six variables were selected using a minimum-run resolution IV experimental design, with a significant affecting Pb2+ removal. Temperature and Pb2+ concentration were significant positive influences, whereas incubation period and agitation speed were significant negative ones. The tested strain modulated the four significant variables for maximum Pb2+ removal using Box-Behnken design. The sequential optimization method was beneficial in increasing biosorption by 4.29%. Dead biomass of P. dendritiformis 17OS was embedded with polyethersulfone to get a hydrophilic adsorptive membrane that can separate Pb2+ easily from aqueous solutions. SEM images and FT-IR analysis proved that the new biosorbent possesses a great structure and a lot of surface functional groups with a negative surface charge of - 9.1 mV. The removal rate of 200 mg/L Pb2+ from water reached 98% using 1.5 g/L of the immobilized biosorbent. The adsorption isotherm studies were displayed to determine the nature of the reaction. The adsorption process was related to Freundlich isotherm which describes the multilayer and heterogeneous adsorption of molecules to the adsorbent surface. In conclusion, dead bacterial cells were immobilized on a polyether sulfone giving it the characteristics of a novel adsorptive membrane for the bioremediation of lead from wastewater. Thus this study proposed a new generation of adsorptive membranes based on polyethersulfone and dead bacterial cells.

Simultaneous decolorization of anionic and cationic dyes by 3D metal-free easily separable visible light active photocatalyst.

To overcome the hard and costly post-treatment separation of ultrathin graphitic carbon nitride nanosheets (UGCN), it was supported on polyurethane foam (PUF). The ratio of PUF/UGCN was optimized for the removal of a mixture of methylene blue (MB) and methyl orange (MO) dyes. The characteristics of the composite photocatalyst and its photocatalytic performance were detailly studied. The X-ray diffraction and Fourier transform infrared results proved the successful preparation of UGCN and PUF and that the PUF/UGCN composite combines the features of both pure materials. The transmission electron microscopy illustrated the ultrathin nanosheet shape of the UGCN, while the scanning electron microscope showed the highly porous 3D-hierarchical structure of PUF. Compared to the pure components, the composite photocatalyst with PUF/UGCN mass ratio of 4 achieved better decolorization of MO and almost same decolorization of MB as UGCN. Neutral pH and 1 g/L of the composite photocatalyst were the optimum conditions for MB/MO mixture decolorization. The composite photocatalyst kept its efficiency for five successive cycles. Hydroxyl radicals were the dominant in the degradation of MB, while superoxide radicals were the most influencer in MO degradation. Conclusively, supporting UGCN onto PUF kept the photocatalytic efficiency of UGCN toward MB decolorization and improved its efficiency toward MO. Moreover, it enabled the reuse of the composite photocatalyst and facilitated the post-treatment separation process.

Neoteric approach for efficient eco-friendly dye removal and recovery using algal-polymer biosorbent sheets: Characterization, factorial design, equilibrium and kinetics.

A new approach of algal-polymer -sheets was performed by the embedding of two algal seaweeds (Ulva fasciata and Sargassum dentifolium) into cellulose acetate (CA) polymer forming two types of cellulose acetate; Ulva (CA-U) and Sargassum (CA-S) sheets. Afterward, the two sheets were characterized then subjected to 3-Rs evaluation (Removal, Recovery, and Reuse) of methylene blue dye (MB). Characterization data exhibited good properties for biosorption process. Algal biosorbents achieved more than twice biosorption capacity (Qmax) after the embedding into the polymer sheet. Additionally, according to factorial design data, the contact time and the dose of biosorbents had positive effects on the biosorption in the two sheets. Freundlich, Langmuir, and pseudo-second order models displayed good represented data in the two sheets. Furthermore, the two sheets (CA-U, followed by CA-S sheet) were successfully given more than 98% adsorption of 273 mg/l MB concentration. Moreover, the recovery and reuse data proved that the two sheets can be performed in good behavior for more than three cycles.