Triphenylarsonium-functionalised gold nanoparticles: potential nanocarriers for intracellular therapeutics.

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.Two new triphenylarsonium alkylthiolate precursors, a thiosulfate zwitterion and a thioacetate salt, have been structurally characterised and their cytotoxicity evaluated against PC3 cells. The arsonium compounds have been used to prepare gold nanoparticles decorated with triphenylarsonium groups.Sheffield Hallam University and Indian Institute of Science (NL)

Methanogens, sulphate and heavy metals: a complex system

Anaerobic digestion (AD) is a well-established technology used for the treatment of wastes and wastewaters with high organic content. During AD organic matter is converted stepwise to methane-containing biogasa renewable energy carrier. Methane production occurs in the last AD step and relies on methanogens, which are rather sensitive to some contaminants commonly found in wastewaters (e.g. heavy metals), or easily outcompeted by other groups of microorganisms (e.g. sulphate reducing bacteria, SRB). This review gives an overview of previous research and pilot-scale studies that shed some light on the effects of sulphate and heavy metals on methanogenesis. Despite the numerous studies on this subject, comparison is not always possible due to differences in the experimental conditions used and parameters explained. An overview of the possible benefits of methanogens and SRB co-habitation is also covered. Small amounts of sulphide produced by SRB can precipitate with metals, neutralising the negative effects of sulphide accumulation and free heavy metals on methanogenesis. Knowledge on how to untangle and balance sulphate reduction and methanogenesis is crucial to take advantage of the potential for the utilisation of biogenic sulphide as a metal detoxification agent with minimal loss in methane production in anaerobic digesters.The research was financially supported by the People Program (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7/2007-2013 under REA agreement 289193

Effects of heavy metals as stress factors on anaerobic digestion processes and biogas production from biomass

Heavy metals affect the biochemical reactions that take place during anaerobic digestion processes of organic matter. In this review, the different effects observed in anaerobic digestion processes and during the production of biomethane and biohydrogen from several substrates contaminated with and/or inheriting heavy metals from the substrates themselves were discussed. It has been found that heavy metals exert important roles in biochemical reactions. Heavy metals like copper, nickel, zinc, cadmium, chromium and lead have been overwhelmingly reported to be inhibitory and under certain conditions toxic in biochemical reactions depending on their concentrations. Heavy metals like iron may also exhibit stimulatory effects, but these effects have been scantily observed. This review also concludes that the severity of heavy metal inhibition depends upon factors like metal concentration in a soluble, ionic form in the solution, type of metal species, and amount and distribution of biomass in the digester or chain of biochemical reactions which constitute the anaerobic digestion process. A majority of studies have demonstrated that the toxic effect of heavy metals like chromium, cadmium and nickel is attributable to a disruption of enzyme function and structure by binding of the metal ions with thiol and other groups on protein molecules or by replacing naturally occurring metals in enzyme prosthetic groups. This review has not found published data on the effects of heavy metals on the hydrolysis stage of anaerobic digestion process chemistry, and hence further studies are required to depict any changes

CODEN: RJCABP BIOSORPTION CHARACTERISTICS OF Cr BIOSORPTION CHARACTERISTICS OF Cr 6+ FROM AQUEOUS SOLUTIONS BY PINUS SYLVESTRIS L. TIMBER FILLINGS

ABSTRACT Pinus Slyvestris L. timber fillings were boiled and utilized as a biosorbent for the removal of Cr 6+ from a synthetic wastewater. The Cr 6+ removal increased from 34.8% to 69.41% as biosorbent dosage increased from 3.0 to 8.0 g/L, while the uptake of Cr 6+ decreased from 6.09 mg/g to 4.78 mg/g as the biosorbent dosage increased from 3.0 to 8.0 g/L, when the initial Cr 6+ concentration was 50 mg/L. The experimental equilibrium data were well described by both the Langmuir and Dubinin-Radushkevich adsorption isotherm models. Based on R 2 values, the Langmuir model fitted the equilibrium biosorption data best, confirming monolayer adsorption of Cr 6+ onto the biosorbent surface. The biosorption kinetics of Cr 6+ was best described by pseudo-second-order kinetics since at all concentrations, the R 2 values were higher than the corresponding pseudo-first order values. The overall results indicated that P. Slyvestris L. is a promising biosorbent for Cr 6+ removal from dilute aqueous solutions

Heavy Metals: Toxicity and Removal by Biosorption

Industrialization, urbanization and various anthropogenic activities such as mining and agriculture have increased releases of toxic heavy metals into the natural environment such as soils, lakes, rivers, groundwaters and oceans. The release of heavy metals in biologically available forms alter both natural and man–made ecosystems. Although some heavy metal ions are essential micronutrients for plant metabolism, they become highly toxic when they occur at high concentrations in soils, groundwaters and waste streams. Moreover, heavy metals are not biodegradable and persist in the environment. Conventional methods for the removal of the heavy metals ions from contaminated wasters and wastewaters include chemical precipitation, electroflotation, ion exchange, reverse osmosis and adsorption onto activated carbon. Recently, pioneering research on biosorption of heavy metals has led to the identification of microbes that are extremely effective in bioconcentrating metals. Biosorption is the binding and concentration of an element from aqueous solutions by organic materials such as microbial biomass. The major advantages of biosorption over conventional treatment methods include low cost, high efficiency, minimization of chemical or biological sludge, regeneration of biosorbents and possible metal recovery. Due to their humic acid content, vermicomposts are a novel and effective variety of biosorbent for removing metallic ions such as Pb, Ni, Cr, Cd and V from wastewaters. The types of biosorbents surveyed in this chapter are fungal biomass, biomass of nonliving, dried brown marine algae, agricultural wastes and residues, composite chitosan biosorbent prepared by coating chitosan, cellulose based sorbents, and bacterial strains

Applications of subcritical and supercritical water conditions for extraction, hydrolysis, gasification, and carbonization of biomass: a critical review

This review summarizes the recent essential aspects of subcritical and supercritical water technology applied tothe extraction, hydrolysis, carbonization, and gasification processes. These are clean and fast technologies which do not need pretreatment, require less reaction time, generate less corrosion and residues, do not usetoxic solvents, and reduce the synthesis of degradation byproducts. The equipment design, process parameters, and types of biomass used for subcritical and supercritical water process are presented. The benefits of catalysis to improve process efficiency are addressed. Bioactive compounds, reducing sugars, hydrogen, biodiesel, and hydrothermal char are the final products of subcritical and supercritical water processes. The present review also revisits advances of the research trends in the development of subcriticaland supercritical water process technologies