Search

Biogas production from agricultural residues represents an effective and sustainable option for handling vast quantities of lignocellulosic waste for meeting the global energy demand. However, the recalcitrance of lignocellulosic biomass due to the presence of cellulose and hemicellulose in a structurally complex lignocellulosic matrix, and the crystallinity of cellulose create a hindrance in biogas production by restricting the availability of fermentable sugars to microbial action. This paper assesses the different pretreatment strategies adopted for making the lignocellulosic biomass amenable to anaerobic digestion by altering the structure of lignocellulose and eliminating lignin, thus increasing the accessibility of microbes to the easily degradable components. The review highlights the advantages and limitations of each technology—physical for size reduction (chipping, milling, extrusion, cavitation), thermal for breaking down of hydrogen bonds (conventional heating, steam explosion, microwave irradiation, hydrothermal), chemical for decreasing the crystallinity and polymerization degree of cellulose (alkalis, acids, gases, oxidizing agents, various solvents), biological for enhancing the digestibility (microbial, enzymatic), and their effect on improving the degradation efficiency and biogas yield. Further, the review discusses the role of some emerging technologies and other less explored options which may require optimization at higher scale so that the confidence in the translation of this knowledge can be increased and this abundantly available raw material can be effectively utilized. With the goal of improving the applicability of pretreatment technologies, some recommendations are put forth so that the efficiency of anaerobic digestion can be increased and the development of pretreatment technologies can be promoted on a large scale. [ABSTRACT FROM AUTHOR]

Fine particulate matter (PM2.5) is one of the main pollutants in the atmosphere and poses a huge threat to public health. Secondary aerosol pollutants that are formed by precursor pollutants in the atmosphere represent a large proportion of PM2.5; furthermore, photochemical reactions play an important role in their transformation processes. This review systematically presents the chemical and toxicological transformations of secondary organic aerosol (SOA), secondary inorganic aerosol (SIA), and metal species in PM2.5 under photochemical conditions. Specifically, major SOAs and SIAs are observed to be formed from volatile organic compounds (VOCs) and sulfur/nitrogen oxides through photochemical reactions, while metal species in PM2.5 participate in a series of photochemical reactions. Additionally, we compare the toxicities of precursor pollutants with their secondary pollutants after photochemical reactions. In general, major SOAs are found to be more toxic than their precursors, while major SIAs are less toxic than their precursors. As different metal species have different toxicities, changes in their toxicities after photoreaction depend on the specific metal and the photochemical reaction. By demonstrating that photochemical reactions can affect the toxicities of PM2.5 components, this review provides a promising perspective toward reducing air pollution and its health risks by investigating the related photochemical reactions. [ABSTRACT FROM AUTHOR]

The acidity of aqueous atmospheric solutions is a key parameter driving both the partitioning of semi-volatile acidic and basic trace gases and their aqueous-phase chemistry. In addition, the acidity of atmospheric aqueous phases, e.g., deliquesced aerosol particles, cloud, and fog droplets, is also dictated by aqueous-phase chemistry. These feedbacks between acidity and chemistry have crucial implications for the tropospheric lifetime of air pollutants, atmospheric composition, deposition to terrestrial and oceanic ecosystems, visibility, climate, and human health. Atmospheric research has made substantial progress in understanding feedbacks between acidity and multiphase chemistry during recent decades. This paper reviews the current state of knowledge on these feedbacks with a focus on aerosol and cloud systems, which involve both inorganic and organic aqueous-phase chemistry. Here, we describe the impacts of acidity on the phase partitioning of acidic and basic gases and buffering phenomena. Next, we review feedbacks of different acidity regimes on key chemical reaction mechanisms and kinetics, as well as uncertainties and chemical subsystems with incomplete information. Finally, we discuss atmospheric implications and highlight the need for future investigations, particularly with respect to reducing emissions of key acid precursors in a changing world, and the need for advancements in field and laboratory measurements and model tools. [ABSTRACT FROM AUTHOR]

Tellurium is a rare metalloid that is vastly produced from copper anode slime, which is a by-product of the copper electrorefining process. Choosing the proper recovery method strongly depends on the slimes composition, mineralogy, and tellurium concentration. In addition, correctly selecting the right method of leaching, purification, and precipitation in economic and environmental processing of the variety of copper anode slimes very much depends on having a thorough understanding of the chemistry, thermodynamics, and kinetics of the recovery process. Despite a wide variety of developments in the recovery of slime, a lack of comprehensive study to help identify the effective factors in the selection of the right process is evident. This article provides a comprehensive literature review on the available tellurium recovering processes from copper anode slime to the final high purity product. This overview is written, hoping to help researchers select and apply the appropriate method in the recovery of tellurium from copper anode slimes of different characteristics. [ABSTRACT FROM AUTHOR]

Biological sulfate reduction is an established method leading to new biotechnologies in wastewater treatment. Batch assays are a powerful tool to support sulfate-reducing bacteria (SRB) research and application; however, their methodology is far from been standardized. The present review critically analyses the experimental conditions used for SRB batch assays in literature, to propose a general experimental framework supporting a future standardized protocol. Batch assays using SRB biomass (SRB-test) were grouped in three different categories depending on their objective: (1) test assessing activity of a SRB culture, (2) test determining the reduction potential of an electron donor, and (3) test determining the feasibility of using different sulfate sources as electron acceptor. Considering the methodologies and results from the reviewed publications, set-up and monitoring conditions are recommended to enhance SRB-tests comparability and reproducibility. The recommendations include the use of lactate as electron donor and sodium sulfate as electron acceptor as controls in the SRB-tests. Finally, due to the difficulty to standardize the biomass source, the microbial characterization of the biomass is recommended. [ABSTRACT FROM AUTHOR]

The article reviews the book "Acid Rain in the Adirondacks: An Environmental History," by Jerry Jenkins, Karen Roy, Charles Driscoll, and Christopher Buerkett.

The article reviews the book "The Basics of Theoretical and Computational Chemistry," by Bernd M. Rode.