Temperature dependence of nickel stabilization in inorganic oxide matrices

Scanning electron microscopy, X-ray diffractometry, X-ray absorption spectroscopy, and other means are used to investigate the effect of thermal treatment temperature, 105-1100 degrees C, on the immobilization of nickel (Ni) by the inorganic oxides of latosol. Ni is more firmly immobilized by the latosol with increasing temperature. Spectral analyses indicate that a shoulder toward the edge-jump appears in the spectra of X-ray absorption near-edge structure for the samples heated at 900 and 1100 degrees C. Moreover, the intensity of the main peak at the edge increases with higher temperature; this information indicates the distortion of the divalent nickel [Ni(II)] environment in the samples heated at 900 and 1100 degrees C. Nevertheless, the distortion is absent from the samples heated at 105 and 500 degrees C. The fact of the distortion of the Ni(II) environment suggests the occurrence of a chemical reaction between the Ni compound and the inorganic matrices of the latosol soil during the heating process at 900 and 1100 degrees C. In addition, the extended X-ray absorption fine structure results correspond well to the X-ray absorption near-edge structure results; the former are supportive of the occurrence of a distorted Ni(II) environment in the samples heated at 900 and 1100 degrees C. The wet-chemistry results show that the samples heated at 900-1100 degrees C leach less Ni than the 105-500 degrees C samples do. The change of the Ni environment is related to the observation that less Ni is leached from the samples heated at 900-1100 degrees C. Furthermore, the pore closing phenomenon is observed only in the 1100 degrees C sample; this phenomenon corresponds with the fact that the 1100 degrees C sample leaches less Ni than the 900 degrees C sample does.     

1985 Directory of Governmental Air Pollution Control Agencies

Abstract

Clay that contains kaolinite has been used extensively as a raw material for manufacturing of bricks and china at 900–1100 °C. This study used clay to stabilize the contaminant chromium(VI) [Cr(VI)] through a heating process at 500–1100 °C. X-ray absorption spectroscopic results indicated that the 500–900 °C heating process transformed hazardous Cr(VI) to nontoxic Cr(III); Cr₂O₃ was the species detected as most abundant. The 1100 °C heating process caused the formation of Cr₂SiO₅, which was not detected in the samples heated at 500–900 °C. Fourier transformed extended X-ray absorption fine structure spectra were fitted by use of WinXAS software. Phase shifts and backscatter(ing) amplitudes for specific atom pairs, based on the crystallographic data for CrO₃ and Cr₂O₃, were theoretically calculated with the FEFF software. The processed XAS data show that the first shell coordination numbers were similar to each other as the temperature was increased from 500 to 900 °C and 1100 °C, implying that their Cr(III) crystallite size was relatively similar. The interatomic distance between the target center element and the first shell for the 500– 1100 °C samples was 1.98Å. The Debye-Waller factor for the 1100 °C sample was increased compared with the 500 and 900 °C samples and probably indicates the formation of Cr₂SiO₅.     

Effect of humic substance on thermal treatment of chromium(VI)-containing latosol soil

Latosol soils contaminated with chromium(VI) [Cr(VI)], which is hazardous, can be recycled as raw materials for porcelain and construction sectors if a proper thermal stabilization process is implemented. This study investigates how thermal treatment affects Cr behavior during the sintering of latosol and deorganic latosol samples; both samples are artificially contaminated with CrO3. Approaches including X-ray absorption spectroscopy, scanning electron microscopy, N2-based Brunauer Emmett Teller surface analyzer, thermogravimetric analyzer/differential scanning calorimeter, and the toxicity characteristic leaching procedure promulgated by Taiwan Environmental Protection Administration are used in this study. After drying the Cr(VI)-contaminated latosol (i.e., containing 37,120 mg of Cr/kg sample) at 105 degrees C, approximately 80% of the doped CrO3 is chemically reduced to Cr(OH)3 by a humic substance naturally existing in the soil. In contrast, in the organics-free CrO3-contaminated latosol dried at 105 degrees C, only 9% of the doped CrO3 is reduced to Cr(OH)3. Heating the samples at 500 and 1100 degrees C transforms hazardous Cr(VI) into Cr(III) that is negligibly toxic; Cr2O3, which is insoluble, is detected as the most abundant Cr species. Moreover, formation of Cr2SiOs, which is suggested to relate to low Cr leaching, is only detected in the sample heated at 1100 degrees C. Surface morphology, surface area, and thermogravimetric analyzer/differential scanning calorimeter results demonstrate that thermal treatment at 1100 degrees C can incur considerable soil sintering/ melting if the humic substance in the soil has been heated off previously. Finally, Cr concentrations in the toxicity characteristic leaching procedure leachates collected from the samples thermally treated at 1100 degrees C for 4 hr are < or =0.21 mg of Cr L(-1) that are much less than the Taiwan Environmental Protection Administration regulatory limit (<5 mg of Cr L(-1)); consequently, these two samples are nonhazardous, and they have the potential for resource recycling. Conversely, Cr concentrations in the leachates from all 500 degrees C and 105 degrees C samples are in the 25.6-1279 mg L(-1) range.     

Molecular study of thermal immobilization of chromium(VI) with clay

Clay that contains kaolinite has been used extensively as a raw material for manufacturing of bricks and china at 900-1100 degrees C. This study used clay to stabilize the contaminant chromium(VI) [Cr(VI)] through a heating process at 500-1100 degrees C. X-ray absorption spectroscopic results indicated that the 500-900 degrees C heating process transformed hazardous Cr(VI) to nontoxic Cr(III); Cr2O3 was the species detected as most abundant. The 1100 degrees C heating process caused the formation of Cr2SiO5, which was not detected in the samples heated at 500-900 degrees C. Fourier transformed extended X-ray absorption fine structure spectra were fitted by use of WinXAS software. Phase shifts and backscatter(ing) amplitudes for specific atom pairs, based on the crystallographic data for CrO3 and Cr2O3, were theoretically calculated with the FEFF software. The processed XAS data show that the first shell coordination numbers were similar to each other as the temperature was increased from 500 to 900 degrees C and 1100 degrees C, implying that their Cr(III) crystallite size was relatively similar. The interatomic distance between the target center element and the first shell for the 500-1100 degrees C samples was 1.98 A. The Debye-Waller factor for the 1100 degrees C sample was increased compared with the 500 and 900 degrees C samples and probably indicates the formation of Cr2SiO5.     

Hydrotalcites and organo‐hydrotalcites as sorbents for removing pesticides from water

Abstract

This paper reports on the adsorption of different organic pesticides by hydrotalcite, hydrotalcite heated to 500°C and organo‐hydrotalcite in aqueous medium by employing adsorption isotherms, and using X‐ray diffraction and infrared spectroscopy techniques. The results suggest that the adsorption capacity of the different materials depends on their nature as well as on the structure, polarity and hydrophobic or anionic nature of the pesticides. The results also show that hydrotalcite, both natural and after calcination at 500°C, is not a good sorbent of hydrophobic pesticides. The data demonstrated that both types of hydrotalcite, however, are very good sorbents of glyphosphate. Furthermore, the organo‐hydrotalcites may be as good sorbents as organo‐montmorillonites for hydrophobic pesticides.     

Studies on the removal of nickel from aqueous solutions using modified riverbed sand

This paper highlights the utility of riverbed sand (RS) for the treatment of Ni(II) from aqueous solutions. For enhancement of removal efficiency, RS was modified by simple methods. Raw and modified sands were characterized by scanning electron microscope (SEM), Energy Dispersive Spectroscopy (EDS), and Fourier Transform Infrared Spectroscopy (FTIR) to investigate the effect of modifying the surface of RS. For optimization of various important process parameters, batch mode experiments were conducted by choosing specific parameters such as pH (4.0–8.0), adsorbent dose (1.0–2.0 g), and metal ion concentrations (5–15 mg/L). Removal efficiency decreased from 68.76 to 54.09 % by increasing the concentration of Ni(II) in solution from 5 to 15 mg/L. Removal was found to be highly dependent on pH of aqueous solutions and maximum removal was achieved at pH 8.0. The process of removal follows first-order kinetics, and the value of rate constant was found to be 0.048 min^?1 at 5 mg/L and 25 °C. Value of intraparticle diffusion rate constant (k _id) was found to be 0.021 mg/g min^1/2 at 25 °C. Removal of Ni(II) decreased by increasing temperature which confirms exothermic nature of this system. For equilibrium studies, adsorption data was analyzed by Freundlich and Langmuir models. Thermodynamic studies for the present process were performed by determining the values of ΔG°, ΔH°, and ΔS°. Negative value of ?H° further confirms the exothermic nature of the removal process. The results of the present investigation indicate that modified riverbed sand (MRS) has high potential for the removal of Ni(II) from aqueous solutions, and resultant data can serve as baseline data for designing treatment plants at industrial scale.     

Characterization of contaminants and evaluation of the suitability for land application of maize and sludge biochars

Prior to the application of biochar as an agricultural improver, attention should be paid to the potential introduction of toxicants and resulting unintended impacts on the environment. In the present study, the concentrations of polycyclic aromatic hydrocarbons (PAHs), heavy metals, and mineral elements were determined in maize and sludge biochars produced at 100 °C increments between 200 and 700 °C. The concentration ranges of total PAHs were 358–5,136 μg kg^?1 in maize biochars and 179–70,385 μg kg^?1 in sludge biochars. The total heavy metals were detected at the following concentrations (mg kg^?1): Cu, 20.4–56.7; Zn, 59.7–133; Pb, 1.44–3.50; Cd, <0.014; Cr, 8.08–21.4; Ni, 4.38–9.82 in maize biochars and Cu, 149–202; Zn, 735–986; Pb, 54.7–74.2; Cd, 1.06–1.38; Cr, 180–247; Ni, 41.1–56.1 in sludge biochars. The total concentrations of PAHs and heavy metals in all maize biochars and most sludge biochars were below the control standards of sludge for agricultural use in China, the USA, and Europe. The leachable Mn concentrations in sludge biochars produced at below 500 °C exceeded the groundwater or drinking water standards of these countries. Overall, all the maize biochars were acceptable for land application, but sludge biochars generated at temperatures between 200 and 500 °C were unsuitable for application as soil amendments due to their potential adverse effects on soil and groundwater quality.     

Molecular study of concentrated copper pollutant with a compost

Humic substance in compost contains various organic functional groups that can sorb metal ions through ionic force. This study used thermal treatment technology to concentrate copper in the heated residues while destroying the humic substance of copper-sorbed kitchen compost. Scanning electron microscopy (SEM) results show that copper clusters were formed in the heated residues. Information from both X-ray diffraction (XRD) patterns and Cu K-edge X-ray absorption spectroscopy (XAS) spectrum indicates that about 30% of the doped Cu(II) was chemically reduced to Cu(I) and Cu(0) when the sample was heated at 500 and 900 degrees C for 2h. The XAS results indicate that after 500 degrees C thermal treatment, the loaded Cu(NO(3))(2) was transformed into CuO (ca. 54%), Cu (ca. 18%), Cu(OH)(2) (ca. 15%), and Cu(2)O (ca.13%). Heating at 900 degrees C caused more transformation into elemental Cu probably due to more release of oxygen.     

Chlorine-bromine exchange during pyrolysis of 1,2,3,4-tetrabromo-dibenzodioxin with various chlorine donors

1,2,3,4-T₄BrDD was pyrolyzed with PVC, HCl and NaCl at 900°C. In all reactions bromine was exchanged with chlorine. During the pyrolysis with PVC at T = 900°C, 69 % of the starting material reacted to give BrCl-dioxins (34.3 %) and 1,2,3,4-T₄CDD (34.7 %). In the reaction with HCl (T = 900°C), 49.2 % BrCl-dioxins and 1,2,3,4-T₄CDD formed. The pyrolysis with NaCl (T = 900°C) yielded 10.5 % BrCl-dioxins and 1,2,3,4-T₄CDD.     

Colloidal diatomite, radionickel, and humic substance interaction: a combined batch, XPS, and EXAFS investigation

This work determined the influence of humic acid (HA) and fulvic acid (FA) on the interaction mechanism and microstructure of Ni(II) onto diatomite by using batch experiments, X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure (EXAFS) methods. Macroscopic and spectroscopic experiments have been combined to see the evolution of the interaction mechanism and microstructure of Ni(II) in the presence of HA/FA as compared with that in the absence of HA/FA. The results indicated that the interaction of Ni(II) with diatomite presents the expected solution pH edge at 7.0, which is modified by addition of HA/FA. In the presence of HA/FA, the interaction of Ni(II) with diatomite increased below solution pH 7.0, while Ni(II) interaction decreased above solution pH 7.0. XPS analysis suggested that the enrichment of Ni(II) onto diatomite may be due to the formation of (≡SO)₂Ni. EXAFS results showed that binary surface complexes and ternary surface complexes of Ni(II) can be simultaneously formed in the presence of HA/FA, whereas only binary surface complexes of Ni(II) are formed in the absence of HA/FA, which contribute to the enhanced Ni(II) uptake at low pH values. The results observed in this work are important for the evaluation of Ni(II) and related radionuclide physicochemical behavior in the natural soil and water environment.     

Improvement of oxygen-containing functional groups on olive stones activated carbon by ozone and nitric acid for heavy metals removal from aqueous phase

Recently, modification of surface structure of activated carbons in order to improve their adsorption performance toward especial pollutants has gained great interest. Oxygen-containing functional groups have been devoted as the main responsible for heavy metal binding on the activated carbon surface; their introduction or enhancement needs specific modification and impregnation methods. In the present work, olive stones activated carbon (COSAC) undergoes surface modifications in gaseous phase using ozone (O₃) and in liquid phase using nitric acid (HNO₃). The activated carbon samples were characterized using N₂ adsorption–desorption isotherm, SEM, pHpzc, FTIR, and Boehm titration. The activated carbon parent (COSAC) has a high surface area of 1194 m²/g and shows a predominantly microporous structure. Oxidation treatments with nitric acid and ozone show a decrease in both specific surface area and micropore volumes, whereas these acidic treatments have led to a fixation of high amount of surface oxygen functional groups, thus making the carbon surface more hydrophilic. Activated carbon samples were used as an adsorbent matrix for the removal of Co(II), Ni(II), and Cu(II) heavy metal ions from aqueous solutions. Adsorption isotherms were obtained at 30 °C, and the data are well fitted to the Redlich–Peterson and Langmuir equation. Results show that oxidized COSACs, especially COSAC(HNO₃), are capable to remove more Co(II), Cu(II), and Ni(II) from aqueous solution. Nitric acid-oxidized olive stones activated carbon was tested in its ability to remove metal ions from binary systems and results show an important maximum adsorbed amount as compared to single systems.     

Desulfurization of Flue Gases in A Fluidized Bed of Modified Limestone

This publication concerns the dry removal of SO₂ from gases using limestone absorbents. It reports bench-scale experiments made with commercial samples of powdered limestone (CaCO₃) activated by addition of a cheap substance, namely CaCl₂. The absorption was carried out in a fluidized bed traversed by the flue gases, between 600° and 900° C. The degree and rate of transformation of CaCO₃ to CaSO₄ in the presence of SO₂ and air have been compared for unmodified and modified absorbents. Initial rates of reaction, and the variation of the rate of absorption with time have been measured. The influence of the SO₂ content of the gas has been assessed. At 700° C, the maximum degree of transformation of activated limestone to sulfate exceeds 90%, whereas untreated CaCO₃ transforms only to 16–20%. At the same temperature, more than 90% of SO₂ contained In a gas carrying 0.35% SO₂ is removed. Because of the much smaller quantity of solid absorbent required, dry absorption processes based on the modified absorbents might get renewed interest. The modified absorbents might also be used for in situ absorption in fluidized bed combustion, in which the temperatures are in the range studied in the present paper.     

Ni-Co bimetallic catalysts on coconut shell activated carbon prepared using solid-phase method for highly efficient dry reforming of methane

Ni-Co bimetallic catalysts supported on coconut shell activated carbon are synthesized using solid-phase method and investigated for dry reforming of methane, to explore the impact of Ni:Co ratio on the catalyst activity and stability. The catalyst performances are evaluated under the temperature varying from 600 to 900 °C and gas hourly space velocity (GHSV) of 7200 mL/h·g-cat. The characterization results show that metal nanoparticles are produced on the support, and the bimetallic catalyst with an explicit Ni:Co ratio (2:1) is the most beneficial for metal particle dispersion and acquires the minimum particle size of 4.41 nm. The bimetallic catalysts with an explicit Ni:Co ratio of 1:2 and 1:1 exhibit a synergistic effect towards the conversions of CH₄ and CO₂, respectively. The experimental results reveal that the highest CH₄ and CO₂ conversions rise to 94.0% and 97.5% within 12 h at 900 °C on average, respectively, assisted with the two bimetallic catalysts. The intensity of disordered carbon and thermal stability are enhanced with the extension of reforming process, contributing to a long-term catalytic stability. Besides, no obvious carbon deposition is detected, leading to a highly catalytic stability for the bimetallic catalysts.

     

Adsorption characteristics of Cu(II) from aqueous solution onto biochar derived from swine manure

The purpose of this study was to investigate adsorption characteristic of swine manure biochars pyrolyzed at 400 °C and 700 °C for the removal of Cu(II) ions from aqueous solutions. The biochars were characterized using BET surface area, Fourier transform infrared spectroscopy (FTIR), zeta potential, scanning electron microscopy/energy dispersive spectrometer (SEM–EDS), and X-ray diffraction (XRD). The adsorption of Cu(II) ions by batch method was carried out and the optimum conditions were investigated. The adsorption processes of these biochars are well described by a pseudo-second-order kinetic model, and the adsorption isotherm closely fitted the Sips model. Thermodynamic analysis suggested that the adsorption was endothermic. The maximum Cu(II) adsorption capacities of biochars derived from fresh and composted swine manure at 400 °C were 17.71 and 21.94 mg g^?1, respectively, which were higher than those at 700 °C. XRD patterns indicated that the silicate and phosphate particles within the biochars served as adsorption sites for Cu(II). The removal of Cu(II) ions from industrial effluent indicated that the fresh swine manure biochar pyrolyzed at 400 °C can be considered as an effective adsorbent.     

Assessment of natural and calcined starfish for the amelioration of acidic soil

Quality improvement of acidic soil (with an initial pH of approximately 4.5) with respect to soil pH, exchangeable cations, organic matter content, and maize growth was attempted using natural (NSF) and calcined starfish (CSF). Acidic soil was amended with NSF and CSF in the range of 1 to 10 wt.% to improve soil pH, organic matter content, and exchangeable cations. Following the treatment, the soil pH was monitored for periods up to 3 months. The exchangeable cations were measured after 1 month of curing. After a curing period of 1 month, the maize growth experiment was performed with selected treated samples to evaluate the effectiveness of the treatment. The results show that 1 wt.% of NSF and CSF (700 and 900 °C) were required to increase the soil pH to a value higher than 7. In the case of CSF (900 °C), 1 wt.% was sufficient to increase the soil pH value to 9 due to the strong alkalinity in the treatment. No significant changes in soil pHs were observed after 7 days of curing and up to 3 months of curing. Upon treatment, the cation exchange capacity values significantly increased as compared to the untreated samples. The organic content of the samples increased upon NSF treatment, but it remains virtually unchanged upon CSF treatment. Maize growth was greater in the treated samples rather than the untreated samples, except for the samples treated with 1 and 3 wt.% CSF (900 °C), where maize growth was limited due to strong alkalinity. This indicates that the amelioration of acidic soil using natural and calcined starfish is beneficial for plant growth as long as the application rate does not produce alkaline conditions outside the optimal pH range for maize growth.     

Estimation of fluorine and chlorine emissions from Spanish structural ceramic industries. The case study of the Bailén area,Southern Spain

This paper assesses F and Cl emissions as atmospheric pollutants in the Bailén area (southern Spain), originated from the raw material used in structural ceramic industries. The area is one of the most important in Spain, with a daily output over three million pieces. The Bailén area features three categories of industries taking into account F emissions (the most important pollutant from ceramic clays):Group I: Those releasing less than 150 ppm F, which use raw materials with low F contents and/or high proportion of calcite, and fire at about 850°C.Group II: Those releasing 150–300 ppm F, whose raw materials show low calcite percentages and bricks are fired between 850–1050°C.Group III: Those releasing more than 300 ppm F, which use clays containing over 1000 ppm F and firing temperatures around 900°C.The emission rate of F increases with increasing F content in the raw material and firing temperature (particularly when exceeding 1000°C). The calcite and clay mineral contents control the F emissions up to 950°C; on the other hand, a high heating rate hinders fluorine emission to some extent. The emission rate of Cl increases with increasing temperature, but in the most cases chlorine is released at concentrations below 30 ppm.Atmospheric contamination in the Bailén area can reach 3 kg/h of fluorine and up to twice of chlorine emission levels permitted, owing to the massive production of structural clay products.     

Properties of biochars from conventional and alternative feedstocks and their suitability for metal immobilization in industrial soil

In contaminated soils, excessive concentrations of metals and their high mobility pose a serious environmental risk. A suitable soil amendment can minimize the negative effect of metals in soil. This study investigated the effect of different biochars on metal (Cu, Pb, Zn) immobilization in industrial soil. Biochars produced at 300 and 600 °C from conventional (MS, maize silage; WP, wooden pellets) and alternative (SC, sewage sludge compost; DR, digestate residue) feedstocks were used as soil amendments at a dosage of 10 % (w/w). The type of feedstock and pyrolysis temperature affected the properties of the biochars and their ability to immobilize metal in soil. Compared to production at 300 °C, all biochars produced at 600 °C had higher pH (6.2–10.7), content of ash (7.2–69.0 %) and fixed carbon (21.1–56.7 %), but lower content of volatile matter (9.7–37.2 %). All biochars except DR biochar had lower dissolved organic carbon (DOC) content (1.4–2.3 g C/L) when made at 600 °C. Only MS and SC biochars had higher cation exchange capacity (25.2 and 44.7 cmol/kg, respectively) after charring at 600 °C. All biochars contained low concentrations of Cd, Cu, Ni, Pb and Zn; Cd was volatilized to the greatest extent during pyrolysis. Based on FTIR analysis and molar ratios of H/C and O/C, biochars had a greater degree of carbonization and aromaticity after charring at 600 °C. The efficiency of the biochars in metal immobilization depended mainly on their pH, ash content, and concentration of DOC. SC and DR biochars were more effective for Cu and Zn immobilization than MS and WP biochars, which makes them attractive options for large-scale soil amendment.     

Emission factor of exhaust gas constituents during the pyrolysis of zinc chloride immersed biosolid

Pyrolysis enables ZnCl₂ immersed biosolid to be reused, but some hazardous air pollutants are emitted during this process. Physical characteristics of biosolid adsorbents were investigated in this work. In addition, the constituents of pyrolytic exhaust were determined to evaluate the exhaust characteristics. Results indicated that the pyrolytic temperature was higher than 500 °C, the specific surface area was >900 m²/g, and the total pore volume was as much as 0.8 cm³/g at 600 °C. For non-ZnCl₂ immersed biosolid pyrolytic exhaust, VOC emission factors increased from 0.677 to 3.170 mg-VOCs/g-biosolid with the pyrolytic temperature increase from 400 to 700 °C, and chlorinated VOCs and oxygenated VOCs were the dominant fraction of VOC groups. VOC emission factors increased about three to seven times, ranging from 1.813 to 21.448 mg/g for pyrolytic temperatures at 400–700 °C, corresponding to the mass ratio of ZnCl₂ and biosolid ranging from 0.25–2.5.     

Thermal Immobilization of Lead Contaminants in Soils Treated in a Fixed- and Fluidized-Bed Incinerator at Moderate Temperatures

Abstract

Artificially lead-contaminated soils with different lead contents (200, 450, 600, and 900 ppm) were thermally immobilized in both fixed-bed and fluidized-bed modes at moderate treating temperatures (less than 500 °C) for various retention times. Cement powder and brick powder were added to the artificially contaminated soils to enhance lead immobilization. Results indicate that increasing treating temperature and time increases the extent of lead immobilization, as determined by the U.S. Environmental Protection Agency's (U.S. EPA) Toxicity Characteristics Leachability Procedure (TCLP). The percentage of lead leached from the soil/ cement mixtures was in the range of less than 0.251%, compared with the range between 13.6% and 40.7% for the corresponding soil/brick mixtures. As the amount of brick dust added to the Pb-doped soil was increased, the specific Pb immobilization effectiveness increased from 0.0675 to 0.149 mg Pb/g brick (for the 20- and 50-gram brick addition, respectively). An increase in air flow rate from 2 to 40 L/min caused a slight decrease in the Pb leaching percentage from 14.96% to 11.59%. Both the Freundlich and Langmuir isotherms give a satisfactory fit (r = 0.945 ~ 0.998) for the data derived from a TCLP test of the thermally-treated soil samples (105 °C and 500 °C) that contained lead contaminants. Sorption of lead contaminants in soil and sorbent matrices was the primary type of chemisorption. The kinetic results indicated that the Pb-doped soil system was too complicated to be described by a simple calculation.     

Effects of hydroxyapatite addition on heavy metal volatility during tannery sludge incineration

The effectiveness of hydroxyapatite (HAP) on volatilization reducing of heavy metals during incineration of tannery sludge was investigated. The tannery sludge was treated through doped with different content of HAP, and then incinerated in the tube furnace at the temperature of 600 °C and 900 °C. The results showed that the volatilization rates decreased by 10.19 % for Pb, 10.17 % for Zn, 7.40 % for Cu and 5.33 % for Cr at 600 °C when the HAP content was raised to 20 %. At 900 °C, the volatilization rates of Pb, Cr and Cu decreased by about 40.0 %, 24.0 % and 9.0 %, respectively, while volatilization of Zn can be considered nearly unchanged at around 5 %. The heavy metals can be stabilized effectively in the incineration after the pyromorphite-like minerals were formed in the sludge doped with HAP.