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•Fe3O4 was synthesized by coprecipitation using TMAOH and thoroughly characterized.•Magnetite nanoparticles successfully remediated aqueous Cr6+ and Pb2+.•Magnetite Langmuir ...adsorption capacities of ∼35 (Cr6+) and ∼53 (Pb2+)mg/g were obtained.•Likely Cr6+ and Pb2+ sorption mechanisms versus pH were described.•Kinetics were pseudo-second order, rate dependent on the number of surface sites.
Magnetic magnetite (Fe3O4) nanoparticles synthesized by chemical co-precipitation were characterized using XRD, TEM, SEM-EDX, FT-IR, ED-XRF, PPMS, point of zero charge (pHpzc) and surface area measurements. As-prepared Fe3O4 nanoparticles were successful for aqueous Cr6+ and Pb2+ removal. Batch adsorption experiments systematically investigated the influence of pH, temperature, contact time and adsorbate/adsorbent concentration on Cr6+ and Pb2+ adsorption. Maximum Cr6+ and Pb2+ removal occurred at pH 2.0 and 5.0, respectively. Sorption data fit pseudo-second order kinetics, indicating a chemical adsorption. The Freundlich, Langmuir, Redlich–Peterson, Toth, Radke and Sips adsorption isotherm models were applied to describe equilibrium data. The Sips and Langmuir models best described Cr6+ and Pb2+ adsorption on magnetite nanoparticles, respectively. The maximum Langmuir adsorption capacities were 34.87 (Cr6+) and 53.11 (Pb2+)mg/g at 45°C, respectively. Fe3O4 nanoparticles are promising potential adsorbents and exhibited remarkable reusability for metal ions removal in water and wastewater treatment.
Summary Using a health impact assessment framework, we estimated the population health effects arising from alternative land-use and transport policy initiatives in six cities. Land-use changes were ...modelled to reflect a compact city in which land-use density and diversity were increased and distances to public transport were reduced to produce low motorised mobility, namely a modal shift from private motor vehicles to walking, cycling, and public transport. The modelled compact city scenario resulted in health gains for all cities (for diabetes, cardiovascular disease, and respiratory disease) with overall health gains of 420–826 disability-adjusted life-years (DALYs) per 100 000 population. However, for moderate to highly motorised cities, such as Melbourne, London, and Boston, the compact city scenario predicted a small increase in road trauma for cyclists and pedestrians (health loss of between 34 and 41 DALYs per 100 000 population). The findings suggest that government policies need to actively pursue land-use elements—particularly a focus towards compact cities—that support a modal shift away from private motor vehicles towards walking, cycling, and low-emission public transport. At the same time, these policies need to ensure the provision of safe walking and cycling infrastructure. The findings highlight the opportunities for policy makers to positively influence the overall health of city populations.
Arsenic's history in science, medicine and technology has been overshadowed by its notoriety as a poison in homicides. Arsenic is viewed as being synonymous with toxicity. Dangerous arsenic ...concentrations in natural waters is now a worldwide problem and often referred to as a 20th–21st century calamity. High arsenic concentrations have been reported recently from the USA, China, Chile, Bangladesh, Taiwan, Mexico, Argentina, Poland, Canada, Hungary, Japan and India. Among 21 countries in different parts of the world affected by groundwater arsenic contamination, the largest population at risk is in Bangladesh followed by West Bengal in India. Existing overviews of arsenic removal include technologies that have traditionally been used (oxidation, precipitation/coagulation/membrane separation) with far less attention paid to adsorption. No previous review is available where readers can get an overview of the sorption capacities of both available and developed sorbents used for arsenic remediation together with the traditional remediation methods. We have incorporated most of the valuable available literature on arsenic remediation by adsorption (∼600 references). Existing purification methods for drinking water; wastewater; industrial effluents, and technological solutions for arsenic have been listed. Arsenic sorption by commercially available carbons and other low-cost adsorbents are surveyed and critically reviewed and their sorption efficiencies are compared. Arsenic adsorption behavior in presence of other impurities has been discussed. Some commercially available adsorbents are also surveyed. An extensive table summarizes the sorption capacities of various adsorbents. Some low-cost adsorbents are superior including treated slags, carbons developed from agricultural waste (char carbons and coconut husk carbons), biosorbents (immobilized biomass, orange juice residue), goethite and some commercial adsorbents, which include resins, gels, silica, treated silica tested for arsenic removal come out to be superior. Immobilized biomass adsorbents offered outstanding performances. Desorption of arsenic followed by regeneration of sorbents has been discussed. Strong acids and bases seem to be the best desorbing agents to produce arsenic concentrates. Arsenic concentrate treatment and disposal obtained is briefly addressed. This issue is very important but much less discussed.
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•Hollow Fe3O4 nanospheres were made by one-pot, template-free solvothermal method.•Magnetite nanospheres were employed to remove heavy metal ions for the first time.•Magnetic ...nanosphere Langmuir adsorption capacities were 19 (Pb2+) and 9mg/g (Cr6+).•Pb2+ and Cr6+ adsorption mechanisms were intensively proposed.•Magnetic separation allows process flexibility during adsorbent recovery and reuse.
Magnetite nanospheres with hollow interiors were synthesized using a simple, one-pot, and template free solvothermal method with ferric chloride as the iron precursor. The composition, surface properties and morphology were studied using X-ray powder diffraction (XRD), energy dispersive X-ray fluorescence (EDXRF), Fourier transform infrared spectroscopy (FTIR), surface area analysis, point of zero charge (pHpzc), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and magnetic moment determination. These mesoporous nanospheres have a SBET=11.3m2/g and a high saturation magnetization of 77.5emu/g. These magnetite nanospheres successfully remediated Cr6+ and Pb2+ from water. The optimum pHs for Cr6+ and Pb2+ adsorption were 4.0 and 5.0, respectively. Adsorption was carried out at 25, 35 and 45°C. The sorption data were fitted using Freundlich, Langmuir, Redlich–Peterson, Sips, Koble–Corrigan, Radke and Prausnitz and Toth adsorption models. The pseudo-second order model better fitted the kinetics data. The Langmuir adsorption capacities of magnetic nanospheres were ∼9 and ∼19mg/g for Cr6+ and Pb2+, respectively. Magnetic collection of these magnetite nanospheres can be used to isolate and regenerate the used adsorbent.
L-Cysteine functionalized magnetite nanoparticles (L-Cyst-Fe
O
NPs) were synthesized by chemical co-precipitation using Fe
and Fe
as iron precursors, sodium hydroxide as a base and L-Cysteine as ...functionalized agent. The structural and morphological studies were carried out using X-ray powder diffraction, transmission electron microscopy, dynamic light scattering, scanning electron microscopy and energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and UV-Vis spectrophotometric techniques. The zeta potential of bare Fe
O
and functionalized L-Cyst-Fe
O
NPs were +28 mV and -30.2 mV (pH 7.0), respectively. The positive surface charge changes to negative imply the presence of L-Cyst monolayer at particle interface. Band gap energy of 2.12 eV bare Fe
O
NPs and 1.4 eV L-Cyst-Fe
O
NPs were obtained. Lead and chromium removal were investigated at different initial pHs, contact time, temperatures and adsorbate-adsorbent concentrations. Maximum Cr
and Pb
removal occurred at pH 2.0 and 6.0, respectively. Sorption dynamics data were best described by pseudo-second order rate equation. Pb
and Cr
sorption equilibrium data were best fitted to Langmuir equation. Langmuir adsorption capacities of 18.8 mg/g (Pb
) and 34.5 mg/g (Cr
) at 45 °C were obtained. Regeneration of exhausted L-Cyst-Fe
O
NPs and recovery of Pb
/Cr
were demonstrated using 0.01 M HNO
and NaOH. L-Cyst-Fe
O
NPs stability and reusability were also demonstrated.
Many transport planners consider urban population density to be a significant determinant of travel behaviour. Much of the evidence for this comes from research in low-density, high-income settings. ...The 2011 Census of India reported mode of travel to work and distance for the first time. We have used these data to investigate the effect of urban density on commute travel patterns at city-level for Indian cities. In addition, we investigated the relationship between travel behaviour and other city-level variables. Using regression, we found almost no independent effect of density on the mode share of walk, cycle, motorised two-wheelers, cars and public transport, after controlling for population and income levels for the cities. Further, it appears that once density levels are greater than ~80 persons per hectare (pph), other factors become more important in determining travel patterns in cities. This evidence has significant implications for urban planning and transport policy in Indian cities and for many other low- and middle-income cities where average density tends to be higher than ~80 pph. For these cities, growth in the use of sustainable transport may not depend on further densification of already dense cities, but on details of how neighbourhoods and streets are designed.
•Census in India reported travel mode and distance of work trips for the first time.•Most Indian cities have higher density than the densest cities in the high-income countries.•Large changes in population density have only negligent effect on travel patterns.•Population size and city-level income are more important determinants of travel behavior.
Providing drinking water with safe arsenic levels in Latin American (LA) countries (a total of 22 countries) is a major current challenge. Arsenic's presence in water has been neglected for many ...decades since it was first reported ~100 years ago in Argentina. The major arsenic source in this region is geogenic. So far, arsenic has been reported in 15 LA countries. Arsenic concentrations in drinking water have been reported up to >200 fold (2000 μg/L) the WHO limit of 10 μg/L. About 14 million people in the arsenic affected LA countries depend on contaminated water characterized by >10 μg/L of arsenic. Low-cost, easy to use, efficient, and sustainable solutions are needed to supply arsenic safe water to the rural and peri-urban population in the affected areas. In the present study, >250 research articles published on various emerging technologies used for arsenic remediation in rural and peri-urban areas of LA countries are critically reviewed. Special attention has been given to arsenic adsorption methods. The manuscript focuses on providing insights into low cost emergent adsorbents with an implementation potential in Latin America. Natural, modified and synthetic adsorbents used for arsenic decontamination were reviewed and compared. Advantages and disadvantages of treatment methods are summarized. Adsorbent selection criteria are developed. Recommendations concerning emerging adsorbents for aqueous arsenic removal in LA countries have also been made.
Technology selection criteria for arsenic remediation in LA. Display omitted
•>250 research articles have been reviewed.•Various arsenic decontamination methods used in LA are critically reviewed.•Advantage, disadvantages and their selection criteria have been summarized.•Special attention has been given to arsenic adsorption methods.•Recommendations on emerging adsorbents in LA have been made.
Environmental (pH, temperature ionic strength, cations, anions) and process (pyrolysis temperature, particle size, adsorbent dosage, initial concentration) parameters were evaluated for ciprofloxacin ...and acetaminophen sorption onto a series of sustainable banana peel biochars. Ciprofloxacin and acetaminophen were chosen as model pharmaceuticals for removal owing to their worldwide presence in aquatic systems. After pyrolytic preparation from 450 to 750 °C, the biochars were qualitatively and quantitatively characterized by physicochemical, morphological, mineralogical and elemental analyses. Batch sorption studies were employed to evaluate the pH effects from 2 to 10, biochar pyrolysis temperatures (450, 550, 650, and 750 °C), particle sizes (30–50, 50–100, 100–150 BSS mesh), adsorbent dosages (0.5, 1.0, 2.0 g/L), adsorbate concentrations (0.5–200 ppm) and uptake temperatures (10, 25, 40 °C) on sorption efficiency. Maximum pharmaceutical sorption is achieved by the biochar prepared at 750 °C. Sorption rate increased with decrease in biochar particle size from 30 to 50 to 100–150 BSS mesh. Relationships between biochar properties and their sorptive potential showed positive correlations with surface area, total pore volume, %C, %ash and C/N molar ratios. Sorption data was modelled using different isotherm models and both kinetic and thermodynamic equations. Maximum Langmuir capacities of ciprofloxacin and acetaminophen on BPBC750 were 23.3 and 40.8 mg/g at 10 °C; 21.0 and 49.93 mg/g at 25 °C and 20.42 and 57.3 mg/g at 45 °C, respectively. Langmuir isotherm fittings and thermodynamic parameters confirmed the exothermic sorption (for ciprofloxacin) and endothermic sorption (for acetaminophen). The role of ionic strength, cations and anions on pharmaceuticals sorption were evaluated. H-bonding, π-π-interactions and pore diffusion were major contributors to pharmaceutical sorption.
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•Sustainable banana peel biochars removed aqueous ciprofloxacin (23.3 mg/g at 10 °C) and acetaminophen (57.3 mg/g at 45 °C).•Adsorption depends on pyrolysis temperature, particle size, pH, dosage, concentration, temperature, ionic strength, and ions.•Isotherm and kinetic models were applied to understand the sorption process.•Sorption mechanisms were proposed.•Correlation of biochar's properties with sorption data was assessed.
A sustainable solution to biomass burning by converting agricultural residues into biochar was provided. Biochar application was investigated to improve soil fertility, sequester carbon, and increase ...crop production. Rice husk (RHBC) and corn stover (CSBC) biochars were obtained by slow pyrolysis at 650° and 550 °C, respectively. RHBC and CSBC were characterized (SEM, SEM-EDX, TEM, FTIR, XRD, elemental analyses, and S
BET
). Unpyrolyzed husks and stover were also used for soil amendments and compared to biochars in different proportions under a controlled incubation environment over 107 days. Fertilizers were not applied. An increase in water holding capacity, total organic carbon, cation exchange capacity, and a decrease in soil CO
2
emission were observed after biochar application to soil
versus
the application of the parent husks or stover. These biochars improved soil fertility and enhanced eggplant crop growth (height, leaf number, fresh and dry weight). In addition, carbon mitigation was achieved because the biochar remained stable in the soil achieving longer term carbon sequestration. Both chars can be used for carbon sequestration and soil amendments.
► Pyrolysis temperature influenced crop residue-derived biochar (BC) properties. ► High pyrolysis temperature led to increased surface area and aromaticity of BC. ► TCE adsorption capacity was ...related to aromaticity and polarity of BC.
Conversion of crop residues into biochars (BCs) via pyrolysis is beneficial to environment compared to their direct combustion in agricultural field. Biochars developed from soybean stover at 300 and 700°C (S-BC300 and S-BC700, respectively) and peanut shells at 300 and 700°C (P-BC300 and P-BC700, respectively) were used for the removal of trichloroethylene (TCE) from water. Batch adsorption experiments showed that the TCE adsorption was strongly dependent on the BCs properties. Linear relationships were obtained between sorption parameters (KM and SM) and molar elemental ratios as well as surface area of the BCs. The high adsorption capacity of BCs produced at 700°C was attributed to their high aromaticity and low polarity. The efficacy of S-BC700 and P-BC700 for removing TCE from water was comparable to that of activated carbon (AC). Pyrolysis temperature influencing the BC properties was a critical factor to assess the removal efficiency of TCE from water.
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