Microalgae-Enabled Wastewater Treatment : A Sustainable Strategy for Bioremediation of Pesticides

Pesticides have been identified as major contaminants of various waterways. Being classified as potential endocrine disrupting compounds, pesticides in aqueous system are highly hazardous to aquatic organisms and the ecosystem. The treatment of pesticide-containing wastewater can be performed through several means, but a wastewater treatment strategy which emphasizes both treatment efficiency and sustainability is a necessity of current time. In this context, bioremediation has been increasingly promoted as an alternative technique for the remediation of diverse pollutants. Particularly, bioremediation which involves the utilization of microalgae for the removal or conversion of pesticides to the harmless or less harmful compounds is becoming a trend. Exploiting microalgae as a tool for wastewater treatment presents multiple advantages over conventional treatment technologies, which include an opportunity to simultaneously treat pesticide-containing wastewater and nutrient recovery for microalgae cultivation as well as less formation of toxic sludge. This review discusses the roles of microalgae in mitigating pesticide pollution issue, while offering an opportunity for nutrient recovery from various wastewater sources. Based on the current laboratory studies, the use of microalgae bioremediation as a promising strategy for pesticide treatment has been rationalized. The establishment of more pilot scale studies is highly encouraged to further facilitate the implementation of this treatment approach for practical application

Surface modification of SiO2 nanoparticles and its impact on the properties of PES-based hollow fiber membrane

In this work, polyethersulfone (PES) hollow fiber membranes incorporated with modified silicon dioxide (SiO2) nanoparticles were prepared and characterized for a water treatment process. Prior to doping preparation, commercial SiO2 nanoparticles were first modified using a sodium dodecyl sulfate (SDS) solution to minimize their agglomeration in the dope solution. The surface-modified nanoparticles were analysed by TEM, BET and zeta potential to determine the particle size, surface area and surface charge, respectively. The effect of modified SiO2 loadings ranging from zero to 4 wt% on the properties of PES-based membranes was examined with respect to thermal stability, hydrophilicity, mechanical strength, pure water flux and protein rejection. The results showed that the modified nanoparticles have reduced agglomeration and greater negative surface charge in comparison to the unmodified nanoparticles. SEM-EDX and FTIR analyses confirmed the presence of modified SiO2 in the PES membrane matrix. It is also found that the thermal stability and hydrophilicity of the composite membranes were improved upon the addition of modified SiO2. The pure water flux and protein rejection of the composite membranes were significantly higher than the control PES membrane. At optimum nanoparticle loading (2 wt%), the composite membrane demonstrated 87.23 L m(-2) h(-1) water flux and 93.6% protein rejection in comparison to 44.2 L m(-2) h(-1) and 80.8% shown by the control PES membrane. The results suggested that the modified SiO2 nanoparticles have great potential to improve membrane water flux without compromising its rejection capability

Adsorptive removal of Cr(VI) and Cu(II) ions from water solution using graphene oxide-manganese ferrite (GMF) nanomaterials

Chromium (Cr) and copper (Cu) are heavy metals known for their dangerous effect towards human health and could enter into human body mainly through ingestion. Over the years, different treatment methods have been used to eliminate heavy metal from raw water source and these include (co)precipitation, coagulation/flocculation, adsorption and ion-exchange. Nonetheless, adsorption is the most prominent method due to its high adsorption capacity and low cost. In this work, graphene oxide-manganese ferrite (GMF) nanomaterials were synthesized and used to remove Cr(VI) and Cu(II) ions from water solution based on adsorption mechanism. The synthesized nanomaterials were characterized using FTIR, BET and TEM prior to use in adsorption process. Batch adsorption studies were carried out to study the adsorption capacity and kinetic properties of the nanomaterials in eliminating two selective heavy metal ions. At optimum pH value, the maximum adsorption capacity for Cr(VI) and Cu(II) are 34.02 and 66.94 mg/g, respectively. The experimental data revealed that the adsorption isotherm best fitted Langmuir model and followed Pseudo second order

Effect of hydrophobicity degree on PVDF hollow fiber membranes for textile wastewater treatment using direct contact membrane distillation

The objectives of this study are to study the effect of hydrophobicity degree of polyvinylidene fluoride (PVDF) hollow fiber membranes blended with different types of additives i.e. ethylene glycol (EG) and polyvinylpyrrolidone (PVP) on textile wastewater application. The degree of hydrophobicity of each membrane was analyzed using contact angle goniometer. The membrane morphology and gas permeability were characterized prior to filtration experiment. Both membranes were tested using direct contact membrane distillation (DCMD) system and their performances were evaluated with respect to water flux and dye removal. This study revealed that the membrane with higher contact angle has greater stability in terms of flux and dye rejection compared to the membrane with low hydrophobic property. This is mainly due to the low surface energy obtained by the highly hydrophobic membrane that prevented the liquids from both sides to penetrate through membrane pore

Polyphenylsulfone-based solvent resistant nanofiltration (SRNF) membrane incorporated with copper-1,3,5 benzenetricarboxylate (Cu-BTC) nanoparticles for methanol separation

Mixed matrix membranes (MMMs) of various properties were prepared for a solvent resistant nanofiltration (SRNF) process by incorporating polyphenylsulfone (PPSU) membranes with self-synthesized copper-1,3,5-benzenetricarboxylate (Cu-BTC) nanoparticles at different loadings. Cu-BTC nanoparticles were homogeneously dispersed in PPSU dope solution prior to the casting process, and their subsequent presence in the PPSU membrane was inferred by a combination of FTIR spectroscopy, TGA, SEM, EDX and AFM analyses. These analyses confirmed the existence of Cu-BTC particles and their distribution pattern in the membrane matrix. Membrane performance in organic solvent nanofiltration was evaluated on the basis of methanol permeance and dye–methanol separation. Results showed that membrane pure methanol flux was significantly improved from 102 L m-2 h-1 in the pristine PPSU membrane to >135 L m-2 h-1 in the 3 wt% Cu-BTC incorporated into PPSU membrane when both membranes were tested at 14 bar. Apart from preferential channels created by Cu-BTC, the existence of interfacial voids in MMMs also contributes to the flux improvement owing to the formation of alternative paths for solvent transportation. Results also showed that the membranes incorporated with low loadings of Cu-BTC (ranging between 0.5 and 1.0 wt%) tended to have smaller molecular weight cut-off (MWCO) than that of pristine PPSU and PPSU incorporated with 3 wt% nanoparticles, leading to smaller surface pore size but better separation efficiency. The improvement in membrane flux and dye rejection at low Cu-BTC loadings could be attributed to the good dispersion of the nanoparticles in the membrane matrix coupled with their improved interfacial contact with the membrane. The newly developed membrane also showed a great improvement in terms of resistance to compaction, suggesting Cu-BTC particles are of importance in increasing membrane rigidity and strength

Performance evaluation of hybrid coagulation/nanofiltration process for AT-POME treatment

The presence of lignin and its degraded products such as tannin and humic acids is the main reason causing the aerobically-treated palm oil mill effluent (AT-POME) to display colour at the point of discharge. In this work, a hybrid method is employed to treat the AT-POME sample that was conventionally treated by biological method. This hybrid method that combines coagulation and nanofiltration (NF) membrane is used to treat the industrial effluent in which the coagulation is conducted prior to NF process. The effects of several variables during coagulation process, i.e., alum concentration, decolouring polymer dosage, cationic polymer dosage and pH on the colour removal and sludge volume production are investigated in order to determine optimum variable conditions for NF process. Under the optimum coagulation conditions (50 mg/L alum, 441 mg/L decolouring polymer, 534 mg/L cationic polymer and pH 9.2), the results showed 92% colour removal with sludge volume as low as 4.1 mL. Further treatment using commercial NF membranes indicated that a permeate sample with complete elimination of colour (almost 100% removal) could be produced with reasonably high water flux

Fabrication polyethersulfone mixed matrix membrane incorporated with silica nanoparticles for BPA removal

The introduction of inorganic nanoparticles in polymeric dope solution for the fabrication process of membrane can potentially enhance the separation performances of membrane without negatively affecting its permeability. In this study, hollow fiber mixed matrix membranes were prepared by incorporating polyethersulfone (PES) membranes with silicon dioxide (SiO2) nanoparticles at different concentration. Prior to separation tests, the prepared membranes were characterized by SEM, EDX, DSC, water contact angle, and FTIR-ATR in order to study the impact of silica nanoparticles on the properties of the membranes. Bisphenol A (BPA) was selected as the subject compound of this study because it is one of the emerging pollutants that have been frequently detected in the water treatment plant (WTP). BPA was spike into the pre-treated water sample taken from the WTP and was used as the feed solution to evaluate the membrane performance in terms of water flux and removal rate. The addition of SiO2 was reported to improve the hydrophilicity of membrane and induce greater micro-voids formation in the membrane structures, leading to increased water flux during BPA filtration process. The presence of more silanol (Si-OH) and siloxane (Si-O-Si) bonding groups resulted from increased SiO2 contents in membrane has improved membrane adsorption rate and further increased BPA removal

The impacts of iron oxide nanoparticles on membrane properties forwater and wastewater applications: A review

The sustainability of clean water supply remains as one of the grand crises faced by today’s world. The rapid expansion of membrane technology has opened up the opportunities for its applications in the sector of water and wastewater treatment. However, the commercial polymeric membranes are suffered from low degree of hydrophilicity and prone to different types of surface fouling. The incorporation of inorganic nanomaterials as nanofillers within polymeric matrix to produce nanocomposite membranes has received enormous attention because of its ability to resolve underlying issues encountered by conventional polymeric membranes. Among various nanoparticles, iron oxide (Fe3O4) nanoparticles have sparked great interest in the fabrication of nanocomposite membranes owing to its intrinsic properties that could improve not only the membrane surface hydrophilicity and antifouling properties but also its removal rates against pollutants via sieving and/or adsorption mechanisms. This review aims to provide insights on the recent advances of Fe3O4-modified microporous membranes for both water and wastewater treatment. Novel strategies such as surface functionalization and nanohybridization of Fe3O4 nanoparticles and its impacts on membrane physicochemical properties and separation performances have been explored and critically reviewed. Finally, the technical challenges in utilizing Fe3O4-modified microporous membranes for potential applications in real operation are also discussed

Fabrication of mixed matric membrane incorporated with modified silica nanoparticles for bisphenol a removal

The introduction of inorganic nanoparticles in polymeric dope solution for the fabrication process of membrane can potentially enhance the separation performances of membrane without negatively affecting its permeability. In this study, hollow fiber mixed matrix membranes were prepared by incorporating polyethersulfone (PES) membranes with silicon dioxide (SiO2) nanoparticles at different concentration. Prior to separation tests, the prepared membranes were characterized by SEM, EDX, DSC, water contact angle, and FTIR-ATR in order to study the impact of silica nanoparticles on the properties of the membranes. Bisphenol A (BPA) was selected as the subject compound of this study because it is one of the emerging pollutants that have been frequently detected in the water treatment plant (WTP). BPA was spike into the pre-treated water sample taken from the WTP and was used as the feed solution to evaluate the membrane performance in terms of water flux and removal rate. The addition of SiO2 was reported to improve the hydrophilicity of membrane and induce greater micro-voids formation in the membrane structures, leading to increased water flux during BPA filtration process. The presence of more silanol (Si-OH) and siloxane (Si-O-Si) bonding groups resulted from increased SiO2 contents in membrane has improved membrane adsorption rate and further increased BPA remova

Preparation and characterization of polysulfone membrane coated with poly(ether block amide) for oxygen enrichment process

Oxygen enriched air (OEA) is widely applied in various areas such as chemical and medical applications. Currently, cryogenic distillation and pressure swing adsorption are the two common technologies that being commercially used for the production of OEA. However, these two techniques are not economically favorable due to required intensive energy and large built-up area. With the advancement of membrane technology in separation process, it garners the interest from both industrial and academic to explore the feasibility of membrane in gas separation. In this study, polysulfone (PSF) hollow fiber membranes with poly(ether block amide) (PEBAX) coating were used for the separation of O2/N2 gas. The hollow fiber membranes used in this work were fabricated by phase inversion spinning process using PSF pellet, along with N,Ndimetyhlacetamide (DMAc) and ethanol (EtOH) as solvent and co-solvent, whereas tetrahydrofuran (THF) as additive. The fabricated membrane exhibited dense structure in the inner layer whereas finger like layer at the outer surface. The formation of this structure was attributed by rapid phase inversion of the solution arose from strong solvent used. The EDX surface mapping analysis confirmed the formation of PEBAX coating on the membrane surface. Gas permeation study in this work illustrated that the pristine PSF membrane exhibited better gas separation performance relative to the PEBAX coated membrane with 20% higher in terms of permeance. The results obtained from this work suggested that the PEBAX coating enhanced the membrane surface but not certain to improve the gas separation performance. Further study on the PEBAX materials for the membrane coating is essential to polish its potential in gas separation