Review on the criteria anticipated for the fabrication of highly efficient ZnO-based visible-light-driven photocatalysts

A comprehensive review on contaminants removal from pharmaceutical wastewater by electrocoagulation process.

Heterogeneous photocatalysis under visible light was employed for the degradation of organic micropollutants (MPs) found in the biologically treated effluents of an urban wastewater treatment plant (UWWTP). The irradiation source consisted in 4 light emitting diodes (LEDs) with a nominal power of 400–500 W m–2 at 417 nm. Metal-free exfoliated graphitic carbon nitride (gCNT), which was synthetized through a simple thermal treatment using dicyandiamide as precursor, was employed as photocatalyst. The gCNT material was characterized using different techniques: N2 adsorption isotherms at 77 K, electron microscopy (scanning and transmission) and diffuse reflectance UV–Vis. The photocatalytic performance of the material was compared to the commercial TiO2-P25, confirming that gCNT led to a remarkable higher removal efficiency of the target MPs. Most of these MPs were removed in less than 10 min to levels below the limit of quantification (carbamazepine > isoproturon > clopidogrel > diclofenac > atenolol > bezafibrate > tramadol > venlafaxine > fluoxetine). Indirect photolysis, resulting from the secondary reactive oxidants generated during the irradiation of the aqueous matrix components, was found to partially contribute for the elimination of the occurring MPs. In addition, the gCNT photocatalyst was immobilized on glass rings for use under continuous mode operation, a minimum residence time of 25 min being required to attain significant removal efficiencies. Phytotoxicity experiments showed that heterogeneous photocatalysis did not enhance the toxicity of the wastewaters.

Metal-free g-C3N4 photocatalysis of organic micropollutants in urban wastewater under visible light

The application of nanoparticles of predominantly zerovalent iron (nanoiron), either unsupported or supported, to the separation and reduction of pertechnetate anions (TcO4-) from complex waste mixtures was investigated as an alternative approach to current waste-processing schemes. Although applicable to pertechnetate-containing waste streams in general, the research discussed here was directed at two specific potential applications at the U.S. Department of Energy s Hanford Site: (1) the direct removal of pertechnetate from highly alkaline solutions, typical of those found in Hanford tank waste, and (2) the removal of dilute pertechnetate from near-neutral solutions, typical of the eluate streams from commercial organic ion-exchange resins that may be used to remediate Hanford tank wastes. It was envisioned that both applications would involve the subsequent encapsulation of the loaded sorbent material into a separate waste form. A high surface area (>200 M2/g) base-stable, nanocrystalline zirconia was used as a support for nanoiron for tests with highly alkaline solutions, while a silica gel support was used for tests with near-neutral solutions. It was shown that after 24 h of contact time, the high surface area zirconia supported nanoiron sorbent removed about 50percent (K-d = 370 L/kg) of the pertechnetate from a pH 14 tank waste simulant containing 0.51 mM TCO4- and large concentrations of Na+, OH-, NO3-, and CO32- for a phase ratio of 360 L simulant per kg of sorbent. It was also shown that after 18 h of contact time, the silica-supported nanoiron removed >95percent pertechnetate from a neutral pH eluate simulant containing 0.076 mM TcO4_ for a phase ratio of 290 L/kg. It was determined that in all cases, nanoiron reduced the Tc(VII) to Tc(IV), or possibly to Tc(V), through a redox reaction. Finally, it was demonstrated that a mixture of 20 mass percent of the solid reaction products obtained from contacting zirconia- supported nanoiron with an alkaline waste solution containing Re(VII), a surrogate for Tc(VII), with 80 mass percent alkali borosilicate based frit heat-treated at 700 degrees C for 4 h sintered into an easily handled glass composite waste form.

Removal of pertechnetate from simulated nuclear waste streams using supported zerovalent iron

Effect of alumina nanoparticles on the antifouling properties of polycarbonate-polyurethane blend ultrafiltration membrane for water treatment

Studies on adsorption, reaction mechanisms and kinetics for photocatalytic degradation of CHD, a pharmaceutical waste.

Nanocomposite polymeric membrane a new trend of water and wastewater treatment: A short review

The environmental pollution is rapidly increasing due to industrialisation. Among all toxic pollutants, heavy metal ions easily bio-accumulate in living organism and such type of accumulation causes detrimental effects in the whole life cycle of all living inhabitants. Protection of the environment for its sustainable development has led to several initiatives been taken for wastewater treatment. In this regard, the present study represents commercially feasible technique for the complete removal of lead and mercury ions from industrial wastewater, by using naturally occurring iron ore slime. It has been observed that Pb(II) and Hg(II) ions can be removed efficiently within a long range of pH. The present study also includes the effect of several process parameters in adsorption of heavy metals such as initial concentration of pollutants and adsorbent, pH and retention time. Adsorption was carried out via both mixing-settling and packed column methods and also adsorption isotherm was investigated here. The results of the characterisation study of slime ensure that the major component is hematite and moreover, high surface area is the influencing parameters for adsorption of heavy metals.

Effective utilization of iron ore slime, a mining waste as adsorbent for removal of Pb(II) and Hg(II)

Heterogeneous photocatalysis in presence of nanoparticles has become a promising pathway for treatment of wastewater containing pharmaceutical components In the present research work, degradation of aqueous solution of chlorhexidine digluconate (CHD), an antibacterial drug, has been investigated using TiO 2 nanoparticles suspension in the annular photo reactor (APR) under continuous mode having the provision of catalyst recovery During the degradation of CHD, the effects of major influencing parameters, ie, substrate to catalyst ratio, flow rate, recycle ratio and temperature on the performance of the photo reactor and its optimization has been performed using Response Surface Methodology (RSM) Moreover, the photocatalytic efficiency of the reactor has been validated by studying the degradation of other antibiotic drugs ie ibuprofen (IBP), atenolol (ATL) and carbamazepine (CBZ) The continuous mode operation in photo reactor has ensured the applicability of the present system in the large volume wastewater treatment The percentage removal of drugs using such reactor having the facility of catalyst recovery is almost same as compared to typical batch photocatalytic system Thus, the present developed system can be utilized for the treatment of wastewater containing pharmaceutical components which are photo catalytically degradable

Studies on the performance of annular photo reactor (APR) for pharmaceutical wastewater treatment

The conventional membrane-separation process for water purification consumes a considerable amount of energy and has some limitations therefore nanotechnology-based membrane-separation process has become an alternative as it consumes less energy and eliminates limitations of conventional process. Mainly, nanograde titanium dioxide, silica, sliver, zeolite, carbon nanotube (CNT), aquaporin, vertically aligned CNTs, block copolymers, and so on. have been incorporated to fabricate nanocomposite membrane, which is very much effective for degradation of organic compounds, bacteria, spores, and virus. Thus it has potential application in water disinfection and removal of organic contaminants from water. Moreover, antifouling properties, chemical, mechanical, and thermal stability of such membranes are enhanced. Therefore, modified membranes have shown higher flux, permeability, and selectivity than conventional membrane. Commercialization of some of the nanomaterial-based membranes has already been started in the field of water purification and rest of them are in lab-scale or pilot-scale development stage.

Santanu Sarkar

Papers

Studies on adsorption, reaction mechanisms and kinetics for photocatalytic degradation of CHD, a pharmaceutical waste.

Nanocomposite polymeric membrane a new trend of water and wastewater treatment: A short review

Effective utilization of iron ore slime, a mining waste as adsorbent for removal of Pb(II) and Hg(II)

Studies on the performance of annular photo reactor (APR) for pharmaceutical wastewater treatment

Nanotechnology-based membrane-separation process for drinking water purification