Experimental and theoretical studies on nitrate removal using epichlorohydrin-modified cross-linked chitosan derived from shrimp waste.

Nitrates level in water is a worldwide problem that represents a risk to the environment and people's health; efforts are currently devoted to the development and implementation of new biomaterials for their removal. In this study, chitosan (Ch) from shrimp waste and the related epichlorohydrin-modified crossover chitosan (Ch-EPI) were used to remove nitrates from aqueous solutions. The mechanism of selective nitrate removal was elucidated and validated by theoretical calculations. The physicochemical performance of Ch and Ch-EPI was investigated through the main parameters pH, adsorption capacity, contact time, initial nitrate concentration, coexisting anions, and temperature. The experimental data were fitted to widely used adsorption kinetic models and adsorption isotherms. The maximum percentage of nitrate adsorption was reached at an equilibrium pH of 4.0 at an adsorbent dose of 2.0 g/L after a contact time of 50 min. Competing anion experiments show that chloride and sulfate ions have minimal and maximal effects on nitrate adsorption by Ch-EPI. Experimental adsorption data are best fitted to pseudo-second-order kinetic and isothermal Langmuir models. The maximum adsorption capacities of Ch and Ch-EPI for nitrate removal were 12.0 mg/g and 38 mg/g, respectively.

The sources, leaching, remediation, and environmental concerns associated with groundwater salinity.

Water resources management and sustainable development depend on the quality of groundwater as a major source of fresh water. As a result of rising water demand in emerging nations and overexploitation, groundwater quality has declined globally in many aquifers. One of the most significant elements that lower the quality of the groundwater is salinization. This review is to provide an overview of various materials that are used in the design and development of innovative chitosan-based nanocomposite polymeric membranes for desalination. Biodegradable, non-toxic, affordable, and easily available, with film-forming ability and poly-functionality, chitosan is an ideal material for a sustainable future. Membrane preparation for desalination using chitosan helps to provide antibacterial and antioxidant activities, great chelating capabilities, and strong adsorption capacity. In this research, we discuss a variety of concepts concerning the different sources of elevated salinity and available desalination methods. A comprehensive framework was also developed to understand the leaching and percolation of salt in groundwater, an essential component of managing risks and ensuring safety. Additionally, we explain the various remediation strategies for reducing groundwater's salt concentration and explore the best method for desalination specifically focused on chitosan.

Chitosan Nanoparticles as Potential Nano-Sorbent for Removal of Toxic Environmental Pollutants.

Adsorption is the most widely used technique for advanced wastewater treatment. The preparation and application of natural renewable and environmentally friendly materials makes this process easier and more profitable. Chitosan is often used as an effective biomaterial in the adsorption world because of its numerous functional applications. Chitosan is one of the most suitable and functionally flexible adsorbents because it contains hydroxyl (-OH) and amine (-NH2) groups. The adsorption capacity and selectivity of chitosan can be further improved by introducing additional functions into its basic structure. Owing to its unique surface properties and adsorption ability of chitosan, the development and application of chitosan nanomaterials has gained significant attention. Here, recent research on chitosan nanoparticles is critically reviewed by comparing various methods for their synthesis with particular emphasis on the role of experimental conditions, limitations, and applications in water and wastewater treatment. The recovery of pollutants using magnetic nanoparticles is an important treatment process that has contributed to additional development and sustainable growth. The application of such nanoparticles in the recovery metals, which demonstrates a "close loop technology" in the current scenarios, is also presented in this review.

Applications of chitosan in environmental remediation: A review.

Environmental biotechnology is the use of biotechnology to develop and regulate biological systems for the remediation of environmental contamination. Nature has gifted ample material for remediation of its resources, among which chitosan is one of the most important and largely available biomaterial globally. Chitosan is a biopolymer obtained by deacetylation of chitin extracted from marine waste and its applications from drug delivery to food additives are broadly available. Chitosan exhibit several properties such as availability, low cost, high biocompatibility, and biodegradability. These properties make it biologically and chemically acceptable for use in various fields. Due to some limitations of pure chitosan, there has been a growing interest in modifying the chitosan in order to improve the original properties and widen the applications of pure phase chitosan. Various modified forms of chitosan and their associated applications are reviewed here with emphasis on their use in environmental remediation. The demand of chitosan in the global industrial market is growing which is briefly explained in this paper. Chitosan is used for water purification since a long time and still progress is going on for making it more efficient in the removal process. It can be used as a flocculent and coagulant, as an adsorbent for removing the contaminants like heavy metals, dyes, pesticides, antibiotics, biological contaminants from wastewater. Soil remediation using chitosan material is explained in this review. Various other applications such as drug delivery, food additives, tissue engineering are thoroughly reviewed.

A review on the advanced leachate treatment technologies and their performance comparison: an opportunity to keep the environment safe.

Landfill application is the most common approach for biowaste treatment via leachate treatment system. When municipal solid waste deposited in the landfills, microbial decomposition breaks down the wastes generating the end products, such as carbon dioxide, methane, volatile organic compounds, and liquid leachate. However, due to the landfill age, the fluctuation in the characteristics of landfill leachate is foreseen in the leachate treatment plant. The focuses of the researchers are keeping leachate from contaminating groundwater besides keeping potent methane emissions from reaching the atmosphere. To address the above issues, scientists are required to adopt green biological methods to keep the environment safe. This review focuses on the assorting of research papers on organic content and nitrogen removal from the leachate via recent effective biological technologies instead of conventional nitrification and denitrification process. The published researches on the characteristics of various Malaysian landfill sites were also discussed. The understanding of the mechanism behind the nitrification and denitrification process will help to select an optimized and effective biological treatment option in treating the leachate waste. Recently, widely studied technologies for the biological treatment process are aerobic methane oxidation coupled to denitrification (AME-D) and partial nitritation-anammox (PN/A) process, and both were discussed in this review article. This paper gives the idea of the modification of the conventional treatment technologies, such as combining the present processes to make the treatment process more effective. With the integration of biological process in the leachate treatment, the effluent discharge could be treated in shortcut and novel pathways, and it can lead to achieving "3Rs" of reduce, reuse, and recycle approach.

Treatment of real wastewater: Kinetic and thermodynamic aspects of cadmium adsorption onto surfactant-modified chitosan beads.

Chitosan (CS) beads of d̅=3.7 ±â€¯0.32 mm diameter containing 97-98% water content were prepared and modified using sodium dodecyl sulfate (SDS) in such a way to form surfactant bilayers on CS beads surface to fabricate surfactant-modified chitosan (SMCS) beads. The characterization of adsorbents was carried out by advanced analytical tools. Adsorption isotherms over a particular range of Cd2+ concentration (10-100 mg/L) in Cd2+ containing distilled water (CCDW) and with varied dose (0.18 to 1.8 g/L) in real wastewater (RWW) were obtained in batch conditions. Kinetic data complied with pseudo-second order model for both the waters. The isotherm data showed that Langmuir model better fitted to the experimental data for CCDW while followed Freundlich isotherm for RWW. Maximum adsorption capacity obtained for CCDW was 125.0 mg/g (C0 = 10-100 mg/L) and 18.0 mg/g when applied to the RWW containing 10.0-11.0 mg/L of Cd2+. The adsorption parameters for Cd2+ removal in RWW were quite different from CCDW. For instance, the optimum dose value increased from 0.45 to 0.9 g/L due to the presence of other contaminants in RWW. It was found that the adsorption of Cd2+ onto SMCS beads was favorable and spontaneous in CCDW as well as in RWW.

Surfactant-modified chitosan beads for cadmium ion adsorption.

Cadmium is one of the most toxic heavy metals, which has been classified as human carcinogen and tetratogen. In the present study chitosan (CS) beads are modified, in a novel way, using sodium dodecyl sulfate (SDS), a well known anionic surfactant. The concentration of SDS has been judiciously selected to form surfactant bilayers on CS surface. These modified beads are designated as surfactant-modified chitosan (SMCS) beads. The adsorbent has been characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The SMCS beads are used as an adsorbent for Cd2+ ion removal (in the initial concentration range of 10-100mg/L) from aqueous medium. The removal follows pseudo-second order kinetic model. SMCS beads show adsorption capacity three times higher than normal CS beads. Adsorption isotherm data fits well to the Langmuir model. The maximum adsorption capacity obtained is 125mg/g. Removal efficiency reached to almost 100% at SMCS dosage of 0.45g/L for lower concentration (10-30mg/L) of Cd2+ ion in 10h, whereas, for higher concentration (40-100mg/L) the removal was ca. 50%.

Novel application of bacteriophage for controlling foaming in wastewater treatment plant- an eco-friendly approach.

This addendum to "Novel application of bacteriophage for controlling foaming in wastewater treatment plant- an eco-friendly approach " includes characteristics of the phages NOC1, NOC2 and NOC3 not discussed in the previous paper. The phage adsorption and host interaction properties, their sensitivity to pH and temperature are inferred. NOC2 is seen to be more temperature resistant while others are not. All the phages show pH sensitivity. There is a variance observed in the behavior of these phages. Also, applicability of the phage based system to large scale reactors is studied and discussed here.

Isolation and characterization of bacteriophages infecting nocardioforms in wastewater treatment plant.

Activated sludge plants (ASP) are associated with the stable foaming problem worldwide. Apart from the physical and chemical treatment methods, biological treatment method has been least explored and may prove to be a novel and ecofriendly approach to tackle the problem of stable foam formation. In ASP Nocardia species are commonly found and are one of the major causes for forming sticky and stable foam. This study describes the isolation and characterization of three Nocardia bacteriophages NOC1, NOC2, and NOC3 for the control of Nocardia species. The bacteriophages isolated in this study have shown promising results in controlling foam producing bacterial growth under laboratory conditions, suggesting that it may prove useful in the field as an alternative biocontrol agent to reduce the foaming problem. To the best of our knowledge to date no work has been published from India related to biological approach for the control of foaming.