Integration of TADOX® technology to improve water reuse efficiency of constructed wetland-treated water

Constructed wetland (CW) is an effective and economical decentralized wastewater treatment (DWWT) method implemented in various developing nations. Such CW-treated water may be good for meeting discharge norms but when it comes to high-end reuse, it requires polishing and integration with advanced oxidation process (AOP)-based treatment. In this pursuit, TERI (The Energy and Resources Institute) Advanced Oxidation Technology (TADOX®) may be able to polish such streams and make the CW-treated water reusable. TADOX utilizes UV-TiO2 Photocatalysis (PC) as a secondary treatment followed by nanomaterial recovery. This study aims at evaluating TADOX treatment to polish treated water from a root zone treatment (RZT) plant. Performance evaluation of the treatments is evaluated based on key parameters for treated sewage water such as chemical oxygen demand (COD), biochemical oxygen demand (BOD), suspended solids, color, pathogens (total and thermotolerant coliforms), and persistent organic pollutants (POPs) such as caffeine, acetaminophen, ibuprofen, and diclofenac. HIGHLIGHTS Root zone treatment (RZT) technology removed 75% COD, 13% BOD, and 67% phosphates.; TADOX® treatment of RZT-treated water led to BOD, COD, NO3-N, and PO4-P % removal as 94, 50, 66, and 100.; TADOX® was effective to remove micropollutants in the range of 79–88%.

TERI advanced oxidation technology (TADOX®) for treatment and rejuvenation of open drains and surface water bodies: making habitats sustainable

Open drains contain sewage waste and find route to surface water bodies mainly due to the absence of dedicated conveyance of wastewater to centralized wastewater treatment facilities. This poses severe environmental, public health and occupational health hazard and there is an urgent need for onsite treatment of open drains. TADOX® (TERI Advanced Oxidation Technology) from TERI (The Energy and Resources Institute, New Delhi) is an advanced approach treat drains using photocatalysis as an advanced oxidation process. This paper presents a case study of an open drain, which when treated with TADOX® Technology, improved water quality parameters meeting the regulatory norms. The untreated open drain did not meet Class E of the Water Quality Criteria laid down by the regulatory body, and attained Class A Water Quality Criteria after end-to-end treatment within 5 h. TADOX® treatment resulted in the removal of 63.5% chemical oxygen demand, 99% biochemical oxygen demand, 96% phosphate, 61% nitrogen, 3 log reduction in E. coli and 4 log reduction in total coliform values with a doubling in dissolved oxygen levels. Micropollutant load reduction of 93.5% in acetaminophen, 96% in sulfamethoxazole, 96% in ibuprofen and 89% in caffeine was also recorded in the study. HIGHLIGHTS TADOX treatment of open drain bypassed biological treatment and resultant treated water complied with Class A of Designated water reuse criteria defined by CPCB, India.; The overall 5-hour end-to-end treatment resulted in significant removal of primary pollutants like 63.5% COD, 99% BOD, 96% phosphate and 61% TKN.; 3 log reduction in E. coli and 4 log reduction in total coliform values.

Zinc peroxide nanomaterial as an adsorbent for removal of Congo red dye from waste water

In the past decade, various natural byproducts, advanced metal oxide composites and photocatalysts have been reported for removal of dyes from water. Although these materials are useful for select applications, they have some limitations such as use at fixed temperature, ultra violet (UV) light and the need for sophisticated experimental set up. These materials can remove dyes up to a certain extent but require long time. To overcome these limitations, a promising adsorbent zinc peroxide (ZnO2) nanomaterial has been developed for the removal of Congo red (CR) dye from contaminated water. ZnO2 is highly efficient even in the absence of sunlight to remove CR from contaminated water upto the permissible limits set by the World Health Organization (WHO) and the United States- Environmental Protection Agency (US-EPA). The adsorbent has a specific property to adjust the pH of the test solution within 6.5-7.5 range irrespective of acidic or basic nature of water. The adsorption capacity of the material for CR dye was 208 mg g(-1) within 10 min at 2-10 pH range. The proposed material could be useful for the industries involved in water purification. The removal of CR has been confirmed by spectroscopic and microscopic techniques. The adsorption data followed a second order kinetics and Freundlich isotherm

Effect of Ni doping on the microstructure and high Curie temperature ferromagnetism in sol-gel derived titania powders

Undoped, 0.05 and 0.5 mol% Ni-doped TiO2 powders were prepared by a modified sol-gel route. The doping effects on the microstructure and magnetism for the powdered samples have been systematically investigated. Doping of Ni in TiO2 inhibited rutile crystal growth. The probable reason for this is discussed on the basis of band calculation based analysis of electronic structures of 3d transition metal-doped TiO2 and the energetic, transformation kinetics and phase stability of anatase over rutile as the function of particle size. Room temperature ferromagnetism (RTFM) with the saturation magnetization of 12 m emu g(-1) and Curie temperature as high as 820K is observed only in case of 0.05 mol% Ni:TiO2 powdered sample, whereas undoped TiO2 was diamagnetic and 0.5 mol% Ni:TiO2 was paramagnetic in nature. The role of any magnetic impurity or any Ni metal in the origin of the RTFM has been ruled out by energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and high resolution TEM (HRTEM) analysis, whereas magnetic force microscopy (MFM) established the presence of magnetic domains, supporting the intrinsic diluted magnetic semiconductor behavior. The observed ferromagnetism has been attributed to the spin ordering through exchange interaction between holes trapped in oxygen orbitals adjacent to Ni substitutional sites

Influence of cobalt doping on the crystalline structure, optical and mechanical properties of ZnO thin films

Uniform and transparent thin films of Zn1 − xCoxO (0 ≤ x ≤ 0.10) were fabricated by sol–gel spin coating technique. Co addition up to x = 0.075, led to refinement in structure and improvement in film quality together with average grain size reduction from 17 nm in undoped ZnO to 15 nm with x = 0.05 and 12 nm with x = 0.10 Co additions. For x ≥ 0.035, CoO (cubic) was detected as the secondary phase. Influence of Co addition on the volume fraction of grain boundaries has been interpreted. Increase in Co content in the range 0 ≤ x ≤ 0.10 led to quenching of near-band edge and blue emissions, decrease in band gap energy (Eg) from 3.36 eV to 3.26 eV, decrease in film thickness and refractive index and an increase in extinction coefficient of Zn1 − xCoxO thin films. The change in nature of stress from compressive to tensile with lower to higher doping of Co is corroborative with the angular peak shift of (002) plane of ZnO lattice. An overall increase in microhardness of Zn1 − xCoxO thin films up to x = 0.05 is attributed to change in microstructure and evolution of secondary phase and as the secondary phase separates out the overall stress is released leading to lowering of hardness after this concentration. Hall–Petch behavior is also studied and found to obey until x = 0.05, however, considerable deviation after this dopant concentration is attributed to the increase in the volume fraction of grain boundaries, which results from the secondary phase separation from this dopant concentration

Environmentally Benign TiO2 Nanomaterials for Removal of Heavy Metal Ions with Interfering Ions present in Tap Water

Availability of clean drinking water is a great challenge in developing countries like India and the presence of heavy metal ions along with interfering ions present in tap water makes them further very difficult to be removed. Following nanotechnology initiatives, we synthesized TiO2 via sol-gel method and tested it for removal of various heavy metal ions like As, Cd, Cr and Pb; highest adsorption and removal efficiency was obtained for Cd when analysed quantitatively using Atomic Absorption Spectrophotometer. Using Scanning Electron Microscopy (SEM), bare TiO2 was observed to have irregular shape while surfactant modified TiO2 had regular spherical morphology. These materials were also tested for anti-bacterial studies against two different pathogenic bacteria i.e. one gram negative strain: Klebsiella pneumoniae and one gram positive strain: Staphylococcus aureu; Thus the overall study opens up numerous possibilities for these materials as adsorbents for removal of heavy metal ions in the presence of competing ions present in tap water together being safe and environmentally benign. (C) 2016 Elsevier Ltd. All rights reserved

Restructural confirmation and photocatalytic applications of graphene oxide-gold composites synthesized by Langmuir-Blodgett method

We present a first report on the use of Langmuir Blodgett (LB) technique for the synthesis of edge decorated graphene oxide gold (GO-Au) nanostructures by simple manipulation of electrostatic interactions. The GO-Au nanostructures when characterized using spectroscopy, surface, chemical and micro structural techniques, displayed unique physical and structural properties. The results re-established the theoretical corroboration that the carboxyl groups are primarily located at the edges of the 2D sheets of GO. The exploitation of air-water interface platform makes this process novel and fundamentally different from existing protocols for synthesis of GO-metal composites. These GO-Au hybrid materials favoured visible-light driven plasmonic photo catalysis together with enhanced charge separation and transportation properties, resulting in the augmentation of photocatalytic activity and conductivity with high transmittance. A plausible reaction mechanism for the degradation of pollutant dye and the role of gold nanoparticles (NPs) on GO has been established

Effect of nominal doping of Ag and Ni on the crystalline structure and photo-catalytic properties of mesoporous titania

Doping at nanoscale and modification of nanocrystal either by binding or interaction is possible if the morphology of the nanocrystal and the properties of the dopant present in the chemical solution are exactly known [30,31]. In other words, the binding energy of the impurity/dopant with respect to the surface of the host lattice, the bonding character and the coordination environment have role to affect the microstructure, grain boundary distribution, surface, optical and photo-catalytic properties of doped materials. In view of this,weadopted a modified sol–gel technique, where dopants (Ag and Ni) are present in the chemical solution for the effective doping in the host matrix. However, the literature reports generally involves higher doping concentrations of these ions, but the novelty of the present work lies in the case specific study of a single and nominal doping concentrations of 0.02 wt.% Ag and Ni in TiO2, which has led to unusual changes with respect to its microstructure, grain boundary distribution, pore size distribution and surface properties, optical and photo-catalytic activity towards complete degradation of organic pollutant dye within few minutes of visible and UV light irradiation