Abstract: In the present study, the effect of ferrous sulfate concentration and total solids on bioleaching of heavy metals from sewage sludge has been examined using indigenous iron-oxidizing microorganisms. The experiments on effects of ferrous sulfate concentrations on bioleaching were carried out using ferrous sulfate of different concentrations (5-20 g L-1) to optimize the concentration of ferrous sulfate for maximum bioleaching. A rapid change in the pH and ORP took place in first 2 days followed by a slow change till 16th day in all the sludge samples. A 10 g L-1 ferrous sulfate concentration was found to be sufficient in metal bioleaching in the following order: Zn: 69%>Cu: 52%>Cr: 46%>Ni: 45. Further, bioleaching using 10 g/L ferrous sulfate was found to be efficient up to 20 g L-1 sludge solids concentration. The results of the present study strongly indicate that using 10 g L-1 ferrous sulfate indigenous iron-oxidizing microorganisms can bring down pH to a value needed for significant metal solubilization.
Abstract: Bioleaching of spent catalyst using moderate thermophilic chemolithotrophic acidophiles in growth medium without Fe source was investigated with two different pulp densities and three different size fractions. All the experiments were conducted on shake flasks at a temperature of 65 °C. The leaching yield of Ni and Al was found to be promising with very high leaching yield of 92-96% followed by Al as 41-76%, which means both Ni and Al leaching were favored by the moderate thermophilic bioleaching compared to the mesophilic bioleaching. The acid consumption was comparatively higher for the 10% pulp density experiments. Comparatively minimal difference in the leaching yield with different size fractions and different pulp densities show no requirement of grinding and using low pulp density less than 10%. This process would rather be economical as well as eco-friendly process for future optimization of the recovery of metal values from spent catalyst.
Abstract: In modern agriculture, polymeric hydrogels are
known as a component able to hold an amount of water due to their
3-dimensional network structure and their tendency to absorb water
in humid environments. In addition, these hydrogels are able to
controllably release the fertilisers and pesticides loaded in them.
Therefore, they deliver these materials to the plants' roots and help
them with growing. These hydrogels also reduce the pollution of
underground water sources by preventing the active components
from leaching. In this study, sIPN acrylamide based hydrogels are
synthesised by using acrylamide free radical, potassium acrylate, and
linear polyvinyl alcohol. Ammonium nitrate is loaded in the hydrogel
as the fertiliser. The effect of various amounts of monomers and
linear polymer, measured in molar ratio, on the swelling rate,
equilibrium swelling, and release of ammonium nitrate is studied.
Abstract: Arsenic in the sediments of the ash lagoons of the coal-fired power plant in Pagbilao, Quezon Province in the Philippines was sequentially extracted to determine its potential for leaching to the groundwater and the adjacent marine environment. Results show that 89% of the As is bound to the quasi-crystalline Fe/Mn oxides and hydroxide matrix in the sediments, whereas, the adsorbed and exchangeable As hosted by the clay minerals, representing those that are easiest to release from the sediment matrix, is below 10% of the acid leachable As. These As in these sediment matrices represent the possible maximum amount of As that can be released and supplied to the groundwater and the adjacent marine environment. Of the 89% reducible As, up to 4% is associated with the easily reducible variety, whereas, the rest is more strongly bonded by the moderately reducible variety. Based on the long-term As content of the lagoon water, the average desorption rate of As is calculated to be very low -- 0.3-0.5% on the average and 0.6% on the maximum. This indicates that As is well-fixed by its sediment matrices in the ash lagoon, attenuating the influx of As into the adjacent groundwater and marine environments.
Abstract: When the results of the total element concentrations using USEPA method 3051A are compared to the sequential extraction analyses (i.e. the sum of fractions BCR1, BCR2 and BRC3), it can be calculated that the recovery values of elements varied between 56.8-% and 69.4-% in the bottom ash, and between 11.3-% and 70.9-% in the fly ash. This indicates that most of the elements in the ashes do not occur as readily soluble forms.
Abstract: This study investigated a strategy of blending lead-laden sludge and Al-rich precursors to reduce the release of metals from the stabilized products. Using PbO as the simulated lead-laden sludge to sinter with γ-Al2O3 by Pb:Al molar ratios of 1:2 and 1:12, PbAl2O4 and PbAl12O19 were formed as final products during the sintering process, respectively. By firing the PbO + γ-Al2O3 mixtures with different Pb/Al molar ratios at 600 to 1000 °C, the lead transformation was determined through X-ray diffraction (XRD) data. In Pb/Al molar ratio of 1/2 system, the formation of PbAl2O4 is initiated at 700 °C, but an effective formation was observed above 750 °C. An intermediate phase, Pb9Al8O21, was detected in the temperature range of 800-900 °C. However, different incorporation behavior for sintering PbO with Al-rich precursors at a Pb/Al molar ratio of 1/12 was observed during the formation of PbAl12O19 in this system. In the sintering process, both temperature and time effect on the formation of PbAl2O4 and PbAl12O19 phases were estimated. Finally, a prolonged leaching test modified from the U.S. Environmental Protection Agency-s toxicity characteristic leaching procedure (TCLP) was used to evaluate the durability of PbO, Pb9Al8O21, PbAl2O4 and PbAl12O19 phases. Comparison for the leaching results of the four phases demonstrated the higher intrinsic resistance of PbAl12O19 against acid attack.
Abstract: Cobalt was acid nitric leached from a mixed cobaltcopper
oxide with variable acid concentration. Resulting
experimental data were used to analyze effects of increase in acid
concentration, based on a shrinking core model of the process. The
mathematical simulation demonstrated that the time rate of the
dissolution mechanism is an increasing function of acid
concentration. It was also shown that the magnitude of the acid
concentration effect is time dependent and the increase in acid
concentration is more effective at earlier stage of the dissolution than
at later stage. The remaining process parameters are comprehensively
affected by acid concentration and their interaction is synergetic.
Abstract: Several trillion cigarettes produced worldwide annually lead to many thousands of kilograms of toxic waste. Cigarette butts (CBs) accumulate in the environment due to the poor biodegradability of the cellulose acetate filters. This paper presents some of the results from a continuing study on recycling CBs into fired clay bricks. Physico-mechanical properties of fired clay bricks manufactured with different percentages of CBs are reported and discussed. The results show that the density of fired bricks was reduced by up to 30 %, depending on the percentage of CBs incorporated into the raw materials. Similarly, the compressive strength of bricks tested decreased according to the percentage of CBs included in the mix. The thermal conductivity performance of bricks was improved by 51 and 58 % for 5 and 10 % CBs content respectively. Leaching tests were carried out to investigate the levels of possible leachates of heavy metals from the manufactured clay-CB bricks. The results revealed trace amounts of heavy metals.
Abstract: All around the world pulp and paper industries are the
biggest plant production with the environmental pollution as the
biggest challenge facing the pulp manufacturing operations. The
concern among these industries is to produce a high volume of papers
with the high quality standard and of low cost without affecting the
environment. This result obtained from this bleaching study show
that the activation of peroxide was an effective method of reducing
the total applied charge of chlorine dioxide which is harmful to our
environment and also show that softwood and hardwood Kraft pulps
responded linearly to the peroxide treatments. During the bleaching
process the production plant produce chlorines. Under the trial stages
chloride dioxide has been reduced by 3 kg/ton to reduce the
brightness from 65% ISO to 60% ISO of pulp and the dosing point
returned to the E stage charges by pre-treating Kraft pulps with
hydrogen peroxide. The pulp and paper industry has developed
elemental chlorine free (ECF) and totally chlorine free (TCF)
bleaching, in their quest for being environmental friendly, they have
been looking at ways to turn their ECF process into a TCF process
while still being competitive. This prompted the research to
investigate the capability of the hydrogen peroxide as catalyst to
reduce chloride dioxide.
Abstract: Mining tailings represent a generating source of rich heavy metal material with a potential danger the public health and the environment, since these metals, under certain conditions, can leach and contaminate aqueous systems that serve like supplying potable water sources. The strategy for this work is based on the observation, experimentation and the simulation that can be obtained by binding real answers of the hydrodynamic behavior of metals leached from mining tailings, and the applied mathematics that provides the logical structure to decipher the individual effects of the general physicochemical phenomenon. The case of study presented herein focuses on mining tailings deposits located in Monte San Nicolas, Guanajuato, Mexico, an abandoned mine. This was considered the contamination source that under certain physicochemical conditions can favor the metal leaching, and its transport towards aqueous systems. In addition, the cartography, meteorology, geology and the hydrodynamics and hydrological characteristics of the place, will be helpful in determining the way and the time in which these systems can interact. Preliminary results demonstrated that arsenic presents a great mobility, since this one was identified in several superficial aqueous systems of the micro watershed, as well as in sediments in concentrations that exceed the established maximum limits in the official norms. Also variations in pH and potential oxide-reduction were registered, conditions that favor the presence of different species from this element its solubility and therefore its mobility.
Abstract: The storage of chemical fertilizers in concrete building often leads to durability problems due to chemical attack. The damage of concrete is mostly caused by certain ammonium salts. The main purpose of the research is to investigate the durability properties of concrete being exposed to ammonium nitrate solution. In this investigation, experiments are conducted on concrete type G50 and G60. The leaching process is achieved by the use of 20% concentration solution of ammonium nitrate. The durability properties investigated are water absorption, volume of permeable voids, and sorptivity. Compressive strength, pH value, and degradation depth are measured after a certain period of leaching. A decrease in compressive strength and an increase in porosity are found through the conducted experiments. Apart from that, the experimental data shows that pH value decreases with increased leaching time while the degradation depth of concrete increases with leaching time. By comparing concrete type G50 and G60, concrete type G60 is more resistant to ammonium nitrate attack.
Abstract: The recovery of metal values and safe disposal of
spent catalyst is gaining interest due to both its hazardous nature and
increased regulation associated with disposal methods. Prior to the
recovery of the valuable metals, removal of entrained deposits limit
the diffusion of lixiviate resulting in low recovery of metals must be
taken into consideration. Therefore, petroleum refinery spent catalyst
was subjected to acetone washing and roasting at 500oC. The treated
samples were investigated for metals bioleaching using
Acidithiobacillus ferrooxidans in batch reactors and the leaching
efficiencies were compared. It was found out that acetone washed
spent catalysts results in better metal recovery compare to roasted
spent. About 83% Ni, 20% Al, 50% Mo and 73% V were leached
using the acetone washed spent catalyst. In both the cases, Ni, V and
Mo was high compared to Al.
Abstract: This paper reviews recent studies and particularly the
effects of Climate Change in the North Tropical Atlantic by studying
atmospheric conditions that prevailed in 2005 ; Coral Bleaching
HotSpot and Hurricane Katrina. In the aim to better understand and
estimate the impact of the physical phenomenon, i.e. Thermal
Oceanic HotSpot (TOHS), isotopic studies of δ18O and δ13C on
marine animals from Guadeloupe (French Caribbean Island) were
carried out. Recorded measures show Sea Surface Temperature (SST)
up to 35°C in August which is much higher than data recorded by
NOAA satellites 32°C. After having reviewed the process that led to
the creation of Hurricane Katrina which hit New Orleans in August
29, 2005, it will be shown that the climatic conditions in the
Caribbean from August to October 2005 have influenced Katrina
evolution. This TOHS is a combined effect of various phenomenon
which represent an additional factor to estimate future climate
changes.
Abstract: Low silica type X (LSX) Zeolite is one of useful
material in many manufacturing due to the advantage properties
including high surface area, stability, microporous crystalline
aluminosilicates and positive ion in an extra–framework. The LSX
was used rice husk silica source which obtained by leaching with
hydrochloric acid and calcination at 500 C. To improve the
synthesis method, the LSX was crystallizated in Teflon–lined
autoclave will expedite deceasing of the amorphous particles. The
mixed gel with composition of 5.5 Na2O : 1.65 K2O : Al2O3 : 2.2
SiO2 : 122 H2O was crystallized in different container
(Polypropylene bottom and Teflon–lined autoclave). The obtained
powder was characterized by X–ray diffraction (XRD), X–ray
fluorescence spectrometry, N2 adsorption-desorption analysis BET
surface area Scanning electron microscopy (SEM) and Fourier
transform infrared spectroscopy to justify the quality of zeolite. The
results showed the crystallized zeolite in Teflon lined autoclave has
102.8 nm of crystal size, 286 m2/g of surface area and fewer amounts
of round amorphous particles when compared with the crystallized
zeolite in Polypropylene.
Abstract: This study aims at using multi-source data to monitor
coral biodiversity and coral bleaching. We used coral reef at Racha
Islands, Phuket as a study area. There were three sources of data:
coral diversity, sensor based data and satellite data.
Abstract: Land degradation is of concern in many countries. People more and more must address the problems associated with the degradation of soil properties due to man. Increasingly, organic soil amendments, such as compost are being examined for their potential use in soil restoration and for preventing soil erosion. In the Czech Republic, compost is the most used to improve soil structure and increase the content of soil organic matter. Land reclamation / restoration is one of the ways to evaluate industrially produced compost because Czech farmers are not willing to use compost as organic fertilizer. The most common use of reclamation substrates in the Czech Republic is for the rehabilitation of landfills and contaminated sites.
This paper deals with the influence of reclamation substrates (RS) with different proportions of compost and sand on selected soil properties–chemical characteristics, nitrogen bioavailability, leaching of mineral nitrogen, respiration activity and plant biomass production. Chemical properties vary proportionally with addition of compost and sand to the control variant (topsoil). The highest differences between the variants were recorded in leaching of mineral nitrogen (varies from 1.36mg dm-3 in C to 9.09mg dm-3). Addition of compost to soil improves conditions for plant growth in comparison with soil alone. However, too high addition of compost may have adverse effects on plant growth. In addition, high proportion of compost increases leaching of mineral N. Therefore, mixture of 70% of soil with 10% of compost and 20% of sand may be recommended as optimal composition of RS.
Abstract: Column leach test has been performed to examine the
behavior of leaching of sodium, calcium and potassium in landfills.
In the column leach apparatus, two different layers of contaminated
and uncontaminated soils of different height ratios (ratio of depth of
contaminated soil to the depth of uncontaminated soil) are taken.
Water is poured from an overhead tank at a particular flowrate to the
inlet of the soil column for a certain ponding depth over the
contaminated soil. Subsequent infiltration causes leaching and the
leachates are collected from the bottom of the column. The
concentrations of Na, Ca and K in the leachate are measured using
flame photometry. The experiments are further extended by changing
the rates of flow from the overhead tank to the inlet of the column in
achieving the same ponding depth. The experiments are performed
for different scenarios in which the height ratios are altered and the
variations of concentrations of Na, Ca, and K are observed. The study
brings an estimation of leaching in landfill sites for different heights
and precipitation intensity where a ponding depth is maintained over
the landfill. It has been observed that the leaching behavior of Na,
Ca, and K are not similar. Calcium exhibits highest amount of
leaching compared to Sodium and Potassium under similar
experimental conditions.
Abstract: Renewable water resources are crucial production
variables in arid and semi-arid regions where intensive agriculture is
practiced to meet ever-increasing demand for food and fiber. This is
crucial for the Dez and Moghan command areas where water delivery
problems and adverse environmental issues are widespread. This
paper aims to identify major problems areas using on-farm surveys of
200 farmers, agricultural extensionists and water suppliers which was
complemented by secondary data and field observations during 2010-
2011 cultivating season. The SPSS package was used to analyze and
synthesis data. Results indicated inappropriate canal operations in
both schemes, though there was no unanimity about the underlying
causes. Inequitable and inflexible distribution was found to be rooted
in deficient hydraulic structures particularly in the main and
secondary canals. The inadequacy and inflexibility of water
scheduling regime was the underlying causes of recurring pest and
disease spread which often led to the decline of crop yield and
quality, although these were not disputed, the water suppliers were
not prepared to link with the deficiencies in the operation of the main
and secondary canals. They rather attributed these to the prevailing
salinity; alkalinity, water table fluctuations and leaching of the
valuable agro-chemical inputs from the plants- route zone with farreaching
consequences. Examples of these include the pollution of
ground and surface resources due to over-irrigation at the farm level
which falls under the growers- own responsibility. Poor irrigation
efficiency and adverse environmental problems were attributed to
deficient and outdated farming practices that were in turn rooted in
poor extension programs and irrational water charges.
Abstract: Several different cements have been tested to evaluate
their potential to leach calcium, chromium and aluminum ions in soft
water environment. The research allows comparing some different
cements in order to the potential risk of water contamination. This
can be done only in the same environment. To reach the results in
reasonable short time intervals and to make heavy metals
measurements with high accuracy, demineralized water was used. In
this case the conditions of experiments are far away from the water
supply practice, but short time experiments and measurably high
concentrations of elements in the water solution are an important
advantage. Moreover leaching mechanisms can be recognized, our
experiments reported here refer to this kind of cements evaluation.
Abstract: Using steelmaking slag as a raw material, aragonite superstructure product had been synthesized via an indirect CO2 mineral sequestration rout. It mainly involved two separate steps, in which the element of calcium is first selectively leached from steelmaking slag by a novel leaching media consisting of organic solvent Tributyl phosphate (TBP), acetic acid, and ultra-purity water, followed by enhanced carbonation in a separate step for aragonite superstructure production as well as efficiency recovery of leaching media. Based on the different leaching medium employed in the steelmaking slag leaching process, two typical products were collected from the enhanced carbonation step. The products were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM), respectively. It reveals that the needle-like aragonite crystals self-organized into aragonite superstructure particles including aragonite microspheres as well as dumbbell-like spherical particles, can be obtained from the steelmaking slag with the purity over 99%.