Indika Herath

Equilibrium and kinetic mechanisms of woody biochar on aqueous glyphosate removal.

We investigated the removal of aqueous glyphosate using woody (dendro) biochar obtained as a waste by product from bioenergy industry. Equilibrium isotherms and kinetics data were obtained by adsorption experiments. Glyphosate adsorption was strongly pH dependent occurring maximum in the pH range of 5-6. The protonated amino moiety of the glyphosate molecule at this pH may interact with π electron rich biochar surface via π-π electron donor-acceptor interactions. Isotherm data were best fitted to the Freundlich and Temkin models indicating multilayer sorption of glyphosate. The maximum adsorption capacity of dendro biochar for glyphosate was determined by the isotherm modeling to be as 44 mg/g. Adsorption seemed to be quite fast, reaching the equilibrium <1 h. Pseudo-second order model was found to be the most effective in describing kinetics whereas the rate limiting step possibly be chemical adsorption involving valence forces through sharing or exchanging electrons between the adsorbent and sorbate. The FTIR spectral analysis indicated the involvement of functional groups such as phenolic, amine, carboxylic and phosphate in adsorption. Hence, a heterogeneous chemisorption process between adsorbate molecules and functional groups on biochar surface can be suggested as the mechanisms involved in glyphosate removal.

Antimony as a global dilemma: Geochemistry, mobility, fate and transport

Elevated concentrations of antimony (Sb) in environmental, biological and geochemical systems originating from natural, geological and anthropogenic sources are of particular global concern. This review presents a critical overview of natural geochemical processes which trigger the mobilization of Sb from its host mineral phases and related rocks to the surrounding environments. The primary source of Sb contamination in the environment is geogenic. The geochemical characteristics of Sb are determined by its oxidation states, speciation and redox transformation. Oxidative dissolution of sulfide minerals and aqueous dissolution are the most prevalent geochemical mechanisms for the release of Sb to the environment. Transformation of mobile forms of Sb is predominantly controlled by naturally occurring precipitation and adsorption processes. Oxyhydroxides of iron, manganese and aluminum minerals have been recognized as naturally occurring Sb sequestrating agents in the environment. Antimony is also immobilized in the natural environment via precipitation with alkali and heavy metals resulting extremely stable mineral phases, such as schafarzikite, tripuhyite and calcium antimonates. Many key aspects, including detection, quantification, and speciation of Sb in different environmental systems as well as its actual human exposure remain poorly understood. Identification of global distribution of most vulnerable Sb-contaminated regions/countries along with aquifer sediments is an urgent necessity for the installation of safe drinking water wells. Such approaches could provide the global population Sb-safe drinking and irrigation water and hinder the propagation of Sb in toxic levels through the food chain. Hence, raising awareness through the mobility, fate and transport of Sb as well as further transdisciplinary research on Sb from global scientific communities will be a crucial stage to establish a sustainable Sb mitigation on a global scale.

Thiolated arsenic in natural systems: What is current, what is new and what needs to be known

Thiolated arsenic compounds are the sulfur analogous substructures of oxo-arsenicals as the arsinoyl (As = O) is substituted by an arsinothioyl (As = S) group. Relatively brief history of thioarsenic research, mostly in the current decade has endeavored to understand their consequences in the natural environment. However, thioarsenic related aspects have by far not attached much research concern on global scale compared to other arsenic species. This review attempts to provide a critical overview for the first time on formation mechanisms of thioarsenicals, their chemistry, speciation and analytical methodologies in order to provide a rational assessment of what is new, what is current, what needs to be known or what should be done in future research. Thioarsenic compounds play a vital role in determining the biogeochemistry of arsenic in sulfidic environments under reducing conditions. Thioarsenic species are widely immobilized by naturally occurring processes such as the adsorption on iron (oxyhydr)oxides and precipitation on iron sulfide minerals. Accurate measurement of thioarsenic species is a challenging task due to their instability upon pH, temperature, redox potential, and concentrations of oxygen, sulfur and iron. Assessment of direct and indirect effects of toxic thioarsenic species on global population those who frequently get exposed to high levels of arsenic is an urgent necessity. Dimethylmonothioarsinic acid (DMMTAV) is the most cytotoxic arsenic metabolite having similar toxicological effects as dimethylarsinous acid (DMAIII) in human and animal tissues. The formation and chemical analysis of thioarsenicals in soil and sediments are highly unknown. Therefore, future research needs to be more inclined towards in determining the molecular structure of unknown thioarsenic complexes in various environmental suites. Contemporary approaches hyphenated to existing technologies would pave the way to overcome critical challenges of thioarsenic speciation such as standards synthesis, structural determination, quantification and sample preservation in future research.

Phytoremediation in Constructed Wetlands

Contamination of water by toxic pollutants through the discharge of municipal, domestic, hospital, and industrial wastewater has become a worldwide environmental problem due to its serious consequences on human health, agricultural crop productivity, and aquatic ecosystems. Phytoremediation using constructed wetlands (CWs) has become a logical solution to improve the quality of contaminated waters by acting as a sink for various contaminants. Hence, the present chapter is aimed to provide a concise discussion of the CWs and its phytoremediation attributes as a plant-based cleanup technology for the remediation of wastewaters. The CWs are complex ecosystems due to variable conditions of hydrology, soil and sediment types, plant species diversity, growing season, and water chemistry. Macrophytes play a vital role bringing necessary physical effects in order to remove and retain pollutants. The hydrology is the key of CWs which defines the species diversity, productivity, and nutrient cycling. The classification of CWs is based on vegetation type, hydrology, and flow direction. Various types of CWs are now being combined into hybrid systems, in order to achieve better treatment performance. Hence, phytoremediation in CWs is being of increasing interest to remediate metals and metalloids, nutrients, volatile organic compounds (VOCs), hydrocarbons, pesticides, pharmaceuticals, explosives, polycyclic aromatic hydrocarbons (PAHs), and pathogens. The relatively brief history of phytoremediation using constructed wetlands has been endeavored for most field applications in order to remediate hazardous pollutants in wastewater and thereby healing the Earth.

Influence of bioenergy waste biochar on proton- and ligand-promoted release of Pb and Cu in a shooting range soil

Presence of organic and inorganic acids influences the release rates of trace metals (TMs) bound in contaminated soil systems. This study aimed to investigate the influence of bioenergy waste biochar, derived from Gliricidia sepium (GBC), on the proton and ligand-induced bioavailability of Pb and Cu in a shooting range soil (17,066mg Pb and 1134mg Cu per kg soil) in the presence of inorganic (sulfuric, nitric, and hydrochloric) and organic acids (acetic, citric, and oxalic). Release rates of Pb and Cu in the shooting range soil were determined under different acid concentrations (0.05, 0.1, 0.5, 1, 5, and 10mM) and in the presence/absence of GBC (10% by weight of soil). The dissolution rates of Pb and Cu increased with increasing acid concentrations. Lead was preferentially released (2.79×10-13 to 8.86×10-13molm-2s-1) than Cu (1.07×10-13 to 1.02×10-13molm-2s-1) which could be due to the excessive Pb concentrations in soil. However, the addition of GBC to soil reduced Pb and Cu dissolution rates to a greater extent of 10.0 to 99.5% and 15.6 to 99.5%, respectively, under various acid concentrations. The increased pH in the medium and different adsorption mechanisms, including electrostatic attractions, surface diffusion, ion exchange, precipitation, and complexation could immobilize Pb and Cu released by the proton and ligands in GBC amended soil. Overall, GBC could be utilized as an effective soil amendment to immobilize Pb and Cu in shooting range soil even under the influence of soil acidity.

Municipal Solid Waste Biochar for Prevention of Pollution From Landfill Leachate

Municipal solid waste (MSW) is produced at an alarming rate, which may have a negative impact on the environment and on human health, if not properly managed. Open landfills are the most common way of disposing of MSW in the developing world. Landfill leachates generated from such open dump sites are directed to surface water bodies with no treatment in most places. Organic and inorganic compounds including organic acids, pesticides, volatile organic compounds, pharmaceuticals, heavy metals, and nutrients in the landfill leachates are extremely important substances to manage. Many different methods are currently in use to treat and fill leachates, such as aerobic biological treatment, anaerobic treatment, physiochemical treatment, coagulation, adsorption, and ion exchange. Among them, carbon adsorption is commonly used method for the remediation of organic and inorganic contaminants. Biochar (BC), a carbonaceous material produced by the pyrolysis of biomass under limited or no oxygen, is an efficient emerging substitute for activated carbon. Biochar from agricultural waste has exceptional capacity for the removal of many different pollutants. Similarly, BC can be potentially produced from the organic materials of the MSW itself, so that it may have a possibility for resource reuse. Hence, this chapter discusses the potential of BC from MSW and its applications to remediate different pollutants in MSW leachate as well as its ability to be used as a landfill cover and as a reactive barrier material.

Correction to: Effects of carbon nanotube and biochar on bioavailability of Pb, Cu and Sb in multi-metal contaminated soil

Unfortunately, in the original publication of the article, Prof. Yong Sik Ok’s affiliation was incorrectly published. The author’s affiliation is as follows.

Correction to: Effects of carbon nanotube and biochar on bioavailability of Pb, Cu and Sb in multi-metal contaminated soil (Environmental Geochemistry and Health, (2017), 39, 6, (1409-1420), 10.1007/s10653-017-9941-6)

Unfortunately, in the original publication of the article, Prof. Yong Sik Ok’s affiliation was incorrectly published. The author’s affiliation is as follows.