Aditi Puri

Magnetite (Fe3O4) silica based organic–inorganic hybrid copper(II) nanocatalyst: a platform for aerobic N-alkylation of amines

A magnetically recoverable, efficient and selective copper based nanocatalyst has been synthesised via covalent grafting of 2-acetylthiophene on a silica coated magnetic nanosupport followed by metallation with copper acetate. The obtained organic–inorganic hybrid nanomaterial has been characterized by electron microscopy techniques (SEM and TEM with EDS), XRD, VSM, FT-IR and AAS. The catalytic performance of the novel nano-catalyst is evaluated in the active transformation of various aromatic amines to industrially-important alkylated amines. The nanocomposites afford high turnover frequency and high selectivity for amines under aerobic conditions. Furthermore, the heterogeneous nature of the catalyst allows easy magnetic recovery and regeneration, which makes the present protocol highly beneficial to address the industrial needs and environmental concerns.

Chemically modified silica gel with 1-{4-[(2-hydroxy-benzylidene)amino]phenyl}ethanone: Synthesis, characterization and application as an efficient and reusable solid phase extractant for selective removal of Zn(II) from mycorrhizal treated fly-ash samples

1-{4-[(2-hydroxy-benzylidene)amino]phenyl}ethanone functionalized silica gel was synthesized and used as a highly efficient, selective and reusable solid phase extractant for separation and preconcentration of trace amount of Zn(II) from environmental matrices. The adsorbent was characterized by fourier transform infrared spectroscopy (FT-IR), elemental analysis, 13C CPMAS NMR spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and BET surface area analysis. The dependence of zinc extraction on various analytical parameters such as pH, type and amount of eluent, sample flow rate and interfering ions were investigated in detail. The material exhibited superior adsorption efficiency for Zn(II) with high metal loading capacity of 1.0 mmol/g under optimum conditions. After adsorption, the recovery (> 98%) of metal ions was accomplished using 1.0 mol/L HNO3 as an eluent. The sorbent was also regenerated by microwave treatment in milder acidic environment (0.1 mol/L HNO3). The lower detection limit and preconcentration factor of the present method were found out to be 0.04 microg/L and 312.5 respectively. The modified silica surface possessed excellent selectivity for the target analytes and the adsorption/desorption process remained effective for at least ten consecutive cycles. The optimized procedure was successfully implemented for the extraction of Zn(II) from mycorrhizal treated fly ash and pharmaceutical samples with reproducible results.

Acetoacetanilide-functionalized Fe3O4 nanoparticles for selective and cyclic removal of Pb2+ ions from different charged wastewaters

Efficient, selective and reusable acetoacetanilide-functionalized Fe3O4 nanoparticles were developed for the first time for the removal of Pb2+ ions. A comprehensive characterization of the functionalized nanoparticles, at different levels of synthesis, was carried out by TEM, EDS, XRD, SEM, FT-IR and VSM. The adsorption equilibrium obeyed the Langmuir isotherm model with a maximum enrichment capacity of 392.2 mg g−1 at 318 K. Pb2+ ions showed quick removal, and the adsorption rate followed pseudo-second-order kinetics. In addition, isotherm and kinetic studies suggested that the adsorption process is controlled by chemical adsorption, involving the complexation of metal ions with the functional groups present on the surface of the functionalized nanoparticles. The thermodynamic analysis revealed that the analyte adsorption is spontaneous, endothermic and energetically driven in nature. Because the superparamagnetism of the Fe3O4 nanoparticles as the magnetic core and silica coat serve as a protective shell, the adsorbent was easily separated and effectively recycled without significant deterioration in its original performance for at least 10 continuous usages. Furthermore, the proposed environmentally benign analytical process was successfully applied for the selective recovery of Pb2+ ions from different charged wastewaters.

Diacetylmonoxime Functionalized Silica Gel: An Efficient and Recyclable Organic Inorganic Hybrid Material for Selective Removal of Copper from Fly Ash Ameliorated Soil Samples

A novel, efficient, highly stable, and reusable organic inorganic hybrid material was synthesized via silanization of silica gel with (3-aminopropyl)trimethoxysilane followed by covalent immobilization with diacetylmonoxime. The grafting was confirmed by FTIR, elemental analysis, 13C CPMAS NMR spectroscopy, SEM, TGA, and BET surface area analysis. The modified solid phase was found to be highly selective for Cu(II) ions under near neutral conditions with a high sorption capacity of 0.93 mmol·g−1 and a preconcentration factor of 250. Isotherm and kinetic parameters correlated well with the Langmuir and pseudo-second-order model. The recovery of analyte was efficiently performed for ten consecutive adsorption-desorption cycles. The present environmentally benign and economical procedure was successfully applied for the separation and preconcentration of copper from fly ash ameliorated soil samples.

Green Chemistry Solutions to Water Pollution

Conventional water treatment processes gradually become more inadequate with the identification of more and more contaminants in the water because of fast growth of population and industrial activities. Therefore, to overcome the challenges associated with traditional processes, there is rapid development of novel chemical technologies. But this growth has turned the attention of environmentalists to complementary actions, like monitoring environmental pollution, reduction of pollutants, and so on, to avoid the negative impacts. In this context, green chemistry solutions provide the most effective way to reduce the harmful effects of water treatment processes by taking into account energy, materials, resource economics, use, and generation of dangerous secondary material, and, finally, the life cycle of the products and their practical recycling into new materials. Some emerging water treatment technologies holding great promises in providing green alternatives for better protection of public health and the environment are discussed in this chapter. Advantages and disadvantages of these technologies are also compared to highlight their existing limitations and future research needs. Hence, it can be said that application of these technologies in association with the emergent knowledge and advances in the manufacturing industries will be highly beneficial to the entire mankind.

CHAPTER 6:Functionalized Silica Gel as Green Material for Metal Remediation

Advancement in industrialization and urbanization is a good indicator of the progress of humanity. However, it has an evil side as well. This advancement is identified as being responsible for deleterious effects on the health of human beings and aquatic biodiversity. Anthropogenic activities like mining and disposal of treated/untreated waste effluents containing toxic metals have resulted in severe deterioration of water quality, rendering serious environmental problems. The basic problem is that the wastewater generated through industries is not given the necessary pretreatment and is discharged directly into water resources. The metals beyond their permissible limits cause maximum negative impacts owing to their long biological half-lives and nondegradable nature. The condition is further worsening in economically deprived countries, where this metal-contaminated wastewater is directly used in various agricultural and day-to-day practices. As a solution to this, the extraction and removal of toxic metal ions from these polluted water resources at an industrial level is of paramount importance. This chapter provides the enthusiastic efforts of the scientific community to disseminate the fundamentals and practices of green analytical methods for metal removal. These methods are based on solid-phase extraction using functionalized silica gel for the separation and preconcentration of metal ions in polluted water resources. Ease of synthesis and extensive application of these organic-inorganic hybrid materials helps to fulfil the commitment of continual environmental improvement by remediating the wastewater.

Bioextraction: The Interface of Biotechnology and Green Chemistry

Industrialization and globalization are causing numerous fluctuations in our ecosystem including increased level of heavy metals. Bioextraction is an alternative to the existing chemical processes for better efficiency with least amount of by-products at optimum utilization of energy. Here is an overview of bioextraction methodology and its associated biological processes, and discussion of the approaches that have been used successfully for withdrawal of heavy metals using metal selective high biomass transgenic plants and microbes from contaminated sites and sub-graded ores. The future of bioextraction is challenging as it offers advantages of operational simplicity, low capital and operating cost, and shorter construction times that no other alternative process can provide. Above all, due to environmental friendliness use of this technology is set to increase.

CHAPTER 2:Green Materials for Sustainable Remediation of Metals in Water

In the evolution of the modern era, urbanization and uncontrolled industrial expansion are the major contributors to damage to the ecosystem, especially harming the aquatic environment through the generation of metal toxic waste. These commercially generated wastes travel through the ecological pathway and pollute the aqueous system. The resulting contaminated water is an affront to human dignity as it jeopardizes both the physical and social health of all people. So, the essence of healthy life is to integrate moral, ethical and economic environmental concerns with chemistry in a constructive way. Sustainable site cleanup and revitalization requires sound green cleanup technologies and materials that restore contaminated water bodies to productive use, reduce associated costs, avoid collateral damage and promote environmental stewardship. Thus, taking into account the environmental and cost benefits, the main body of the chapter emphasizes the comprehensive and generalized view of available green technologies, their processes and applications for metal remediation.