Mitra Naghdi

Adsorption study of environmentally relevant concentrations of chlortetracycline on pinewood biochar.

The presence of pharmaceutically active compounds (PhACs) in water and wastewater has raised concerns because of potential environmental impacts and thus their removal is of high importance. The adsorption behavior of chlortetracycline (CTC) from aqueous solution on raw and activated pinewood biochar was studied at 298 K. The effect of initial pH of the solution was studied by performing the experiment at three different pHs (1, 5 and 9). At each pH, CTC showed varied electrostatic charge (+1, 0 and -1, respectively) which affected its adsorption. The results indicated that CTC followed Langmuir isotherm and the related parameters were calculated. Also, it was observed that the maximum adsorption occurred at pH1. The adsorption capacity of CTC for raw and activated biochar was at least 2.1 and 208.3mg/g adsorbent, respectively. The characteristics of biochars were studied using zeta potential analyzer, laser size analyzer and scanning electron microscopy (SEM). The results showed that raw and activated biochars are promising candidates for removal of CTC from water due to the acidic character of pinewood that can result in better interaction with ionizable compounds at lower pHs.

Degradation of chlortetracycline using immobilized laccase on Polyacrylonitrile-biochar composite nanofibrous membrane

The continuous release of antibiotic compounds through wastewater effluent into environment has raised concerns about their potential problems for different organisms. Enzymatic degradation with laccase is a green option for removal of pharmaceutical compounds from aqueous media. In this study, laccase was immobilized onto homemade Polyacrylonitrile-biochar composite nanofibrous membrane and the obtained biocatalyst was employed for removal of chlortetracycline, a widely used antibiotic, from aqueous media in continuous mode. The results showed that the immobilized laccase has improved storage, temperature and pH stability compared to free laccase. Also, it retained more than 50% of its initial activity after 7cycles of ABTS oxidation which indicated improved enzyme reusability. Finally, while using immobilized laccase for degradation of chlortetracycline in continuous mode exhibited 58.3%, 40.7% and 22.6% chlortetracycline removal efficiency at flux rates of 1, 2 and 3mL/h∙cm2.

A review on the important aspects of lipase immobilization on nanomaterials

Lipase is one of the most widely used enzymes and plays an important role in biotechnological and industrial processes including food, paper, and oleochemical industries, as well as in pharmaceutical applications. However, its aqueous solubility and instability make its application relatively difficult and expensive. The immobilization technique is often used to improve lipase performance, and the strategy has turned out to be a promising method. Immobilized lipase on nanomaterials (NMs) has shown superiority to the free lipase, such as improved thermal and pH stability, longer stable time, and the capacity of being reused. However, immobilization of lipase on NMs also sometimes causes activity loss and protein loading is relatively lowered under some conditions. The overall performance of immobilized lipase on NMs is influenced by mechanisms of immobilization, type of NMs being used, and physicochemical features of the used NMs (such as particle size, aggregation behavior, NM dimension, and type of coupling/modifying agents being used). Based on the specific features of lipase and NMs, this review discusses the recent developments, some mechanisms, and influence of NMs on lipase immobilization and their activity. Multiple application potential of the immobilized lipases has also been considered.

Removal of pharmaceutical compounds in water and wastewater using fungal oxidoreductase enzymes

Due to recalcitrance of some pharmaceutically active compounds (PhACs), conventional wastewater treatment is not able to remove them effectively. Therefore, their occurrence in surface water and potential environmental impact has raised serious global concern. Biological transformation of these contaminants using white-rot fungi (WRF) and their oxidoreductase enzymes has been proposed as a low cost and environmentally friendly solution for water treatment. The removal performance of PhACs by a fungal culture is dependent on several factors, such as fungal species, the secreted enzymes, molecular structure of target compounds, culture medium composition, etc. In recent 20 years, numerous researchers tried to elucidate the removal mechanisms and the effects of important operational parameters such as temperature and pH on the enzymatic treatment of PhACs. This review summarizes and analyzes the studies performed on PhACs removal from spiked pure water and real wastewaters using oxidoreductase enzymes and the data related to degradation efficiencies of the most studied compounds. The review also offers an insight into enzymes immobilization, fungal reactors, mediators, degradation mechanisms and transformation products (TPs) of PhACs. In brief, higher hydrophobicity and having electron-donating groups, such as amine and hydroxyl in molecular structure leads to more effective degradation of PhACs by fungal cultures. For recalcitrant compounds, using redox mediators, such as syringaldehyde increases the degradation efficiency, however they may cause toxicity in the effluent and deactivate the enzyme. Immobilization of enzymes on supports can enhance the performance of enzyme in terms of reusability and stability. However, the immobilization strategy should be carefully selected to reduce the cost and enable regeneration. Still, further studies are needed to elucidate the mechanisms involved in enzymatic degradation and the toxicity levels of TPs and also to optimize the whole treatment strategy to have economical and technical competitiveness.

Biological synthesis of metallic nanoparticles: plants, animals and microbial aspects

The green synthesis (GS) of different metallic nanoparticles (MNPs) has re-evaluated plants, animals and microorganisms for their natural potential to reduce metallic ions into neutral atoms at no expense of toxic and hazardous chemicals. Contrary to chemically synthesized MNPs, GS offers advantages of enhanced biocompatibility and thus has better scope for biomedical applications. Plant, animals and microorganisms belonging to lower and higher taxonomic groups have been experimented for GS of MNPs, such as gold (Au), silver (Ag), copper oxide (CuO), zinc oxide (ZnO), iron (Fe2O3), palladium (Pd), platinum (Pt), nickel oxide (NiO) and magnesium oxide (MgO). Among the different plant groups used for GS, angiosperms and algae have been explored the most with great success. GS with animal-derived biomaterials, such as chitin, silk (sericin, fibroin and spider silk) or cell extract of invertebrates have also been reported. Gram positive and gram negative bacteria, different fungal species and virus particles have also shown their abilities in the reduction of metal ions. However, not a thumb rule, most of the reducing agents sourced from living world also act as capping agents and render MNPs less toxic or more biocompatible. The most unexplored area so far in GS is the mechanism studies for different natural reducing agents expect for few of them, such as tea and neem plants. This review encompasses the recent advances in the GS of MNPs using plants, animals and microorganisms and analyzes the key points and further discusses the pros and cons of GS in respect of chemical synthesis.

Nanotechnology to Remove Contaminants

Emerging contaminants will be a major challenge for human health and environment since their concentrations are increasing. Contaminants occur in air, soil and aquatic media, then finally end up in drinking water. Contaminants cause many health issues to living organisms, by disruption of endocrine systems and feminization of male fish, for instance. Therefore, prevention of contaminant release, and cleaning of contaminated media are needed. Many processes, including physical separation, biological treatment and chemical transformation have been set up to remove contaminants. Here we review methods to remove contaminants using nanomaterials, such as nanoparticles, nanotubes, and nanostructured membranes. New processes based on nanostructured materials such as TiO2 nanowires or nanofiltration membrane can achieve up to 95 % removal of contaminants.

Instrumental approach toward understanding nano-pollutants

Nano-pollutants (NPLTs) have recently raised global concerns due to their possible harmful impact on environment and human health. However, until date, information on the occurrence, fate and toxicity of NPLTs in environment is scant. The knowledge gap can be attributed to the lack of advanced and sophisticated methodologies for the precise detection and characterization of NPLTs at lower concentration in complex matrices, such as surface water, wastewater, soil and food. This review briefly discusses the performance of classical methods for characterization and study of the properties of NPLTs. The important properties include shape, size, aggregation state, chemical composition and structure. Chromatographic, microscopic and spectroscopic techniques have been developed for detection and quantitative estimation of fabricated or naturally existed NPLTs in different matrices. Often, combination of these techniques is required for the separation, purification and accurate estimation. For better detection and understanding of the initial steps of interaction with the environmental matrices, pollution sources, such as wastewater and industrial discharges, must be selected as sampling points. Understanding the dynamics of agglomeration, and decantation will allow to estimate the plume of transport to delimit the potential effects.