Ishtiaq A. Qazi

Evaluation of the adsorption potential of titanium dioxide nanoparticles for arsenic removal.

The adsorption potential of titanium dioxide (TiO2) nanoparticles for removing arsenic from drinking water was evaluated. Pure and iron-doped TiO2 particles are synthesized via sol-gel method. The synthesized TiO2 nanoparticles were then immobilized on ordinary sand for adsorption studies. Adsorption isotherms were conducted on the synthesized nanoparticles as well as the sand coated with TiO2 nanoparticles under varying conditions of air and light, namely, the air-sunlight (A-SL), air-light (AL), air-dark (AD) and nitrogen-dark (ND). X-ray diffraction (XRD) analysis showed that the pure and iron-doped TiO2 nanoparticles were in 100% anatase crystalline phase with crystal sizes of 108 and 65 nm, respectively. Adsorption of arsenic on the three adsorbents was non-linear that could be described by the Freundlich and Langmuir adsorption models. Iron doping enhanced the adsorption capacity of TiO2 nanoparticles by arresting the grain growth and making it visible light responsive resulting in a higher affinity for arsenic. Similarly, the arsenic removal by adsorption on the sand coated with TiO2 nanoparticles was the highest among the three types of sand used. In all cases, As(V) was adsorbed more compared with As(III). The solution pH appeared to be the most important factor in controlling the amount of arsenic adsorbed.

Removal of Fluoride from Drinking Water Using Modified Immobilized Activated Alumina

The study describes the removal of fluoride from drinking water using modified immobilized activated alumina (MIAA) prepared by sol-gel method. The modification was done by adding a specific amount of alum during the sol formation step. The fluoride removal efficiency of MIAA was 1.35 times higher as compared to normal immobilized activated alumina. A batch adsorption study was performed as a function of adsorbent dose, contact time, stirring rate, and initial fluoride concentration. More than 90% removal of fluoride was achieved within 60 minutes of contact time. The adsorption potential of MIAA was compared with activated charcoal which showed that the removal efficiency was about 10% more than the activated charcoal. Both the Langmuir and Freundlich adsorption isotherms fitted well for the fluoride adsorption on MIAA with the regression coefficient R2 of 0.99 and 0.98, respectively. MIAA can both be regenerated thermally and chemically. Adsorption experiments using MIAA were employed on real drinking water samples from a fluoride affected area. The study showed that modified immobilized activated alumina is an effective adsorbent for fluoride removal.

Metallic Nanoparticle (TiO2 and Fe3O4) Application Modifies Rhizosphere Phosphorus Availability and Uptake by Lactuca sativa.

Application of engineered nanoparticles (NPs) with respect to nutrient uptake in plants is not yet well understood. The impacts of TiO2 and Fe3O4 NPs on the availability of naturally soil-bound inorganic phosphorus (Pi) to plants were studied along with relevant parameters. For this purpose, Lactuca sativa (lettuce) was cultivated on the soil amended with TiO2 and Fe3O4 (0, 50, 100, 150, 200, and 250 mg kg(-1)) over a period of 90 days. Different techniques, such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman, and Fourier transform infrared spectroscopy (FTIR) were used to monitor translocation and understand the possible mechanisms for phosphorus (P) uptake. The trends for P accumulation were different for roots (TiO2 > Fe3O4 > control) and shoots (Fe3O4 > TiO2 > control). Cystine and methionine were detected in the rhizosphere in Raman spectra. Affinities of NPs to adsorb phosphate ions, modifications in P speciation, and NP stress in the rhizosphere had possibly contributed to enhanced root exudation and acidification. All of these changes led to improved P availability and uptake by the plants. These promising results can help to develop an innovative strategy for using NPs for improved nutrient management to ensure food security.

EFFECT OF COATING THICKNESS ON THE PROPERTIES OF TiN COATINGS DEPOSITED ON TOOL STEELS USING CATHODIC ARC PVD TECHNIQUE

Titanium nitride (TiN) widely used as hard coating material, was coated on tool steels, namely on high-speed steel (HSS) and D2 tool steel by physical vapor deposition method. The study concentrated on cathodic arc physical vapor deposition (CAPVD), a technique used for the deposition of hard coatings for tooling applications, and which has many advantages. The main drawback of this technique, however, is the formation of macrodroplets (MDs) during deposition, resulting in films with rougher morphology. Various standard characterization techniques and equipment, such as electron microscopy, atomic force microscopy, hardness testing machine, scratch tester, and pin-on-disc machine, were used to analyze and quantify the following properties and parameters: surface morphology, thickness, hardness, adhesion, and coefficient of friction (COF) of the deposited coatings. Surface morphology revealed that the MDs produced during the etching stage, protruded through the TiN film, resulting in film with deteriorated surface features. Both coating thickness and indentation loads influenced the hardness of the deposited coatings. The coatings deposited on HSS exhibit better adhesion compared to those on D2 tool steel. Standard deviation indicates that the coating deposited with thickness around 6.7 μm showed the most stable trend of COF versus sliding distance.

Photocatalytic degradation of nitro and chlorophenols using doped and undoped titanium dioxide nanoparticles

Pure and Ag-TiO2 nanoparticles were synthesized, with the metallic doping being done using the Liquid Impregnation (LI) method. The resulting nanoparticles were characterized by analytical methods such as scanning electron micrographs (SEMs), Energy Dispersive Spectroscopy (EDS), and X-ray diffraction (XRD). XRD analysis indicated that the crystallite size of TiO2 was 27nm to 42nm while the crystallite size of Ag-TiO2 was 11.27nm to 42.52 nm. The photocatalytic activity of pure TiO2 and silver doped TiO2 was tested by photocatalytic degradation of p-nitrophenol as a model compound. Ag-TiO2 nanoparticles exhibited better results (98% degradation) as compared to pure TiO2 nanoparticles (83% degradation) in 1 hour for the degradation of p-nitrophenol. Ag-TiO2 was further used for the photocatalytic degradation of 2, 4-dichlorphenol (99% degradation), 2,5- dichlorophenol (98% degradation), and 2, 4, 6-trichlorophenol (96% degradation) in 1 hour. The degree of mineralization was tested by TOC experiment indicating that 2, 4-DCP was completely mineralized, while 2, 5-DCP was mineralized upto 95 percent and 2, 4, 6-TCP upto 86 percent within a period of 2 hours.

Comparative solid phase photocatalytic degradation of polythene films with doped and undoped TiO 2 nanoparticles

Comparative photocatalytic degradation of polythene films was investigated with undoped and metal (Fe, Ag, and Fe/Ag mix) doped TiO2 nanoparticles under three different conditions such as UV radiation, artificial light, and darkness. Prepared photocatalysts were characterized by XRD, SEM, and EDS techniques. Photocatalytic degradation of the polythene films was determined by monitoring their weight reduction, SEM analysis, and FTIR spectroscopy. Weight of PE films steadily decreased and led to maximum of 14.34% reduction under UV irradiation with Fe/Ag mix doped TiO2 nanoparticles and maximum of 14.28% reduction under artificial light with Ag doped TiO2 nanoparticles in 300 hrs. No weight reduction was observed under darkness. Results reveal that polythene-TiO2 compositing with metal doping has the potential to degrade the polythene waste under irradiation without any pollution.

Arsenic removal from aqueous solution using pure and metal-doped titania nanoparticles coated on glass beads: adsorption and column studies

Nanosizedmetal oxide, Titania, provides high surface area and specific affinity for the adsorption of heavymetals, including arsenic (As), which is posing a great threat to the world population due to its carcinogenic nature. In this study, As(III) adsorption was studied on pure and metal- (Ag- and Fe-) doped Titania nanoparticles. The nanoparticles were synthesized by liquid impregnation method with some modifications, with crystallite size in the range of 30 to 40 nm. Band gap analysis, using Kubelka-Munk function showed a shift of absorption band from UV to visible region for themetal-doped Titania. Effect of operational parameters like dose of nanoparticles, initial As(III) concentration, and pH was evaluated at 25°C. The data obtained gave a good fit with Langmuir and Freundlich isotherms and the adsorption was found to conform to pseudo-second-order kinetics. In batch studies, over 90% of arsenic removal was observed for both types of metal-doped Titania nanoparticles from a solution containing up to 2 ppm of the heavy metal. Fixed bed columns of nanoparticles, coated on glass beads, were used for As(III) removal under different operating conditions. Thomas and Yoon-Nelson models were applied to predict the breakthrough curves and to find the characteristic column parameters useful for process design. The columns were regenerated using 10% NaOH solution.

MACRODROPLET REDUCTION AND GROWTH MECHANISMS IN CATHODIC ARC PHYSICAL VAPOR DEPOSITION OF TiN FILMS

Cathodic arc physical vapor deposition (CAPVD) a technique used for the deposition of hard coatings for tooling applications has many advantages. The main drawback of this technique is the formation of macrodroplets (MDs) during deposition resulting in films with rougher morphology. The MDs contamination and growth mechanisms was investigated in TiN coatings over high-speed steel, as a function of metal ion etching, substrate bias, and nitrogen gas flow rate; it was observed that the latter is the most important factor in controlling the size and number of the macrodroplets.

Development of a Method for the Determination of Chromium and Cadmium in Tannery Wastewater Using Laser-Induced Breakdown Spectroscopy

This paper illustrates systematic development of a convenient analytical method for the determination of chromium and cadmium in tannery wastewater using laser-induced breakdown spectroscopy (LIBS). A new approach was developed by which liquid was converted into solid phase sample surface using absorption paper for subsequent LIBS analysis. The optimized values of LIBS parameters were 146.7 mJ for chromium and 89.5 mJ for cadmium (laser pulse energy), 4.5 μs (delay time), 70 mm (lens to sample surface distance), and 7 mm (light collection system to sample surface distance). Optimized values of LIBS parameters demonstrated strong spectrum lines for each metal keeping the background noise at minimum level. The new method of preparing metal standards on absorption papers exhibited calibration curves with good linearity with correlation coefficients, R2 in the range of 0.992 to 0.998. The developed method was tested on real tannery wastewater samples for determination of chromium and cadmium.

Immobilization in cement mortar of chromium removed from water using titania nanoparticles

Because of the high toxicity of chromium, particularly as Cr (VI), it is removed from industrial effluents before their discharge into water bodies by a variety of techniques, including adsorption. Ultimate disposal of the sludge or the adsorbate, however, is a serious problem. While titania, in nanoparticle form, serves as a very good adsorbent for chromium, as an additive, it also helps to increase the compressive strength of mortar and concrete. Combining these two properties of the material, titania nanoparticles were used to adsorb chromium and then added to mortar up to a concentration of 20% by weight. The compressive strength of the resulting mortar specimens that replaced 15% of cement with chromium laden titania showed an improved strength than that without titania, thus confirming that this material had positive effect on the mortar strength. Leachate tests using the Toxicity Characteristics Leaching Procedure (TCLP) confirmed that the mortar sample chromium leachate was well within the permissible limits. The proposed technique thus offers a safe and viable method for the ultimate disposal of toxic metal wastes, in general, and those laden waste chromium, in particular.