Characterization of Compost with Respect to its Content of Heavy Metals. Part II: Sample Preparation

Abstract

This paper forms part of a study aimed at the development of a procedure for the determination of heavy metals in compost. The present paper deals with the sample preparation stage, including subdividing laboratory samples and reduction of the particle size.

The effect of particle size reduction on the random error due to the analysis of test portions was examined. It was found that milling for 20min in a quartz planet ball mill yields sufficiently homogeneous test samples. As the milling capacity of this device is too small, prior to milling subdivision of the laboratory sample is required. Subdivision before drying is recommended for practical reasons.     

Evaluation of grinding methods for pellets preparation aiming at the analysis of plant materials by laser induced breakdown spectrometry

It has been demonstrated that laser induced breakdown spectrometry (LIBS) can be used as an alternative method for the determination of macro (P, K, Ca, Mg) and micronutrients (B, Fe, Cu, Mn, Zn) in pellets of plant materials. However, information is required regarding the sample preparation for plant analysis by LIBS. In this work, methods involving cryogenic grinding and planetary ball milling were evaluated for leaves comminution before pellets preparation. The particle sizes were associated to chemical sample properties such as fiber and cellulose contents, as well as to pellets porosity and density. The pellets were ablated at 30 different sites by applying 25 laser pulses per site (Nd:YAG@1064 nm, 5 ns, 10 Hz, 25 J cm⁻²). The plasma emission collected by lenses was directed through an optical fiber towards a high resolution echelle spectrometer equipped with an ICCD. Delay time and integration time gate were fixed at 2.0 and 4.5 μs, respectively. Experiments carried out with pellets of sugarcane, orange tree and soy leaves showed a significant effect of the plant species for choosing the most appropriate grinding conditions. By using ball milling with agate materials, 20 min grinding for orange tree and soy, and 60 min for sugarcane leaves led to particle size distributions generally lower than 75 μm. Cryogenic grinding yielded similar particle size distributions after 10 min for orange tree, 20 min for soy and 30 min for sugarcane leaves. There was up to 50% emission signal enhancement on LIBS measurements for most elements by improving particle size distribution and consequently the pellet porosity.     

Influence of particle size and particle loading on mechanical and dielectric properties of biochar particulate-reinforced polymer nanocomposites

This research work emphasizes using pulverized biochar obtained by the pyrolysis of rice husk as a particulate reinforcement in unsaturated polyester matrix. The influence of particle size and particle loading on the mechanical and dielectric properties of particulate composites were investigated. The mean size of particles obtained through pulverizing using ball mill varied from 510 to 45 nm when milled for a duration ranging from 6 to 30 h. The particle loading in the composite varied from 0.5 to 2.5 wt%. The impact strength of the specimen having particle loading of 2.5 wt% with 45 nm particle size increased by 77.50%, and its dielectric constant increased by 7% when compared to that of cured pure resin; however, the tensile strength decreased. The biochar particles were subjected to X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), and atomic force microscopy (AFM) analysis for characterization. Morphological studies were performed on tested samples by scanning electron microscope.     

Pyrolysis kinetics and chemical composition of Hazro coal according to the particle size

Summary The relationship between particle size and chemical composition of Hazro coal (origin: SE Anatolia, Turkey) has been examined by elemental analysis and by thermogravimetric pyrolysis. The chemical composition of the coal was determined by grinding sample particles physically and separating according to their size in mm by sieving. Particle size distribution of the coal and chemical composition of these fractions were given. The coal has been non-isothermally pyrolyzed in a thermogravimetric analyzer to determine the kinetic factors. Thermal gravimetric (TG/DTG) experiments were performed from ambient temperature to 800°C under a nitrogen atmosphere at heating rate 10 K min^-1 with five different particle size ranges. Kinetic parameters of the samples were determined using a Coats and Redfern kinetic model, assuming a first-order reaction. Depending on the particle size of the coal samples, the mean activation energy values varied between 49.1 and 84.6 kJ mol^-1. The results discussed indicate that activation energies increase as the particle size decreases.     

Effect of grinding method on the analysis of essential oil from <Emphasis Type="Italic">Baccharis articulata</Emphasis> (Lam.) Pers.

Grinding methods were evaluated aiming to determine yield and composition of essential oils (EOs) from Baccharis articulata (Lam) Pers., called as carqueja, a native plant from South Brazil. Cryogenic, knife (with and without cooling) and ball mills were used. The major constituents found in EOs were β-pinene, caryophyllene, spathulenol and caryophyllene oxide, but differences in 21 compounds were observed. All grinding processes reduced monoterpenes and oxygenated sesquiterpenes with concentration of hydrocarbon sesquiterpenes. The sesquiterpenes (hydrocarbons and oxygenated) were found from 63.55 to 86.02% while the monoterpene hydrocarbons’ concentration ranged from 13.98 to 36.45%. Plants milled with knife mill provided EOs with profile similar to those not grinded. Despite the lower working temperature, cryogenic milling resulted in smaller EO yield (0.40 ± 0.03%) in comparison to other grinding methods (yields from 0.50 ± 0.02 to 0.56 ± 0.03%) and different chromatographic profile. Microscopic analysis showed the smaller particle size provided by cryogenic grinding, which leads to glandular trichome rupture and consequently to loss of EOs. This study showed that grinding should be carefully evaluated to provide reproducible results in essential oil analysis.     

Preparation and preliminary certification of two new Polish CRMs for inorganic trace analysis

Preparation and characterization of two new reference materials of biological origin, namely: Tea Leaves (INCT-TL-1) and Mixed Polish Herbs (INCT-MPH-2) is described. The raw materials were ground in an agate ball mill, sieved through a nylon sieve, collecting fraction of particle size: Æ£67 ·m, and carefully homogenized. Preliminary homogeneity testing by XRF method and final checking of homogeneity by NAA after distribution of the materials into containers revealed that they are sufficiently homogeneous at least for sample size ≥100 mg. Both materials were prepared in amounts exceeding 40 kg and certified on the basis of a worldwide interlaboratory comparison, in which 109 laboratories from 19 countries participated. The method of data evaluation leading to assignment of certified values was essentially the same as that used previously in this Laboratory, but supplemented by additional data from the analysis of a CRM which was sent to the participants and analyzed by them along with the candidate reference materials. In addition the results for a few elements by very accurate developed methods in this Laboratory were obtained and used to support the certification process. Analytical uncertainties and stability uncertainties were quantified to arrive at combined uncertainties of the certified values. So far 18 elements in INCT-TL-1 and 21 in INCT-MPH-2 could be certified.     

Bovine liver sample preparation and micro-homogeneity study for Cu and Zn determination by solid sampling electrothermal atomic absorption spectrometry

This work describes a systematic study for the bovine liver sample preparation for Cu and Zn determination by solid sampling electrothermal atomic absorption spectrometry. The main parameters investigated were sample drying, grinding process, particle size, sample size, microsample homogeneity, and their relationship with the precision and accuracy of the method. A bovine liver sample was prepared using different drying procedures: (1) freeze drying, and (2) drying in a household microwave oven followed by drying in a stove at 60 °C until constant mass. Ball and cryogenic mills were used for grinding. Less sensitive wavelengths for Cu (216.5 nm) and Zn (307.6 nm), and Zeeman-based three-field background correction for Cu were used to diminish the sensitivities. The pyrolysis and atomization temperatures adopted were 1000 °C and 2300 °C for Cu, and 700 °C and 1700 °C for Zn, respectively. For both elements, it was possible to calibrate the spectrometer with aqueous solutions. The use of 250 μg of W + 200 μg of Rh as permanent chemical modifier was imperative for Zn. Under these conditions, the characteristic mass and detection limit were 1.4 ng and 1.6 ng for Cu, and 2.8 ng and 1.3 ng for Zn, respectively. The results showed good agreement (95% confidence level) for homogeneity of the entire material (> 200 mg) when the sample was dried in microwave/stove and ground in a cryogenic mill. The microsample homogeneity study showed that Zn is more dependent on the sample pretreatment than Cu. The bovine liver sample prepared in microwave/stove and ground in a cryogenic mill presented results with the lowest relative standard deviation for Cu than Zn. Good accuracy and precision were observed for bovine liver masses higher than 40 μg for Cu and 30 μg for Zn. The concentrations of Cu and Zn in the prepared bovine liver sample were 223 mg kg^− 1 and 128 mg kg^− 1, respectively. The relative standard deviations were lower than 6% (n = 5). The accuracy of the entire procedure was checked with bovine liver from NIST (1577b) and determination of Cu and Zn using flame atomic absorption spectrometry after microwave-assisted sample digestion.     

New human hair certified reference material for methylmercury and trace elements

 A new human hair certified reference material (NIES CRM No. 13) for mercury speciation and trace element analysis was prepared at the National Institute for Environmental Studies (NIES), Environmental Agency of Japan. Scalp hair from Japanese males, which is identical with the original material for the previous human hair CRM (NIES CRM No. 5), was used. Special attention was paid to reduce contamination from a grinding vessel during the preparation procedure. A newly-prepared ceramic/Teflon disc mill was used for cryogenic grinding of the hair. 1,000 bottles (3 g each) were produced after sieving and blending of the hair powder. Certified values for total mercury and methylmercury, as well as other trace elements of toxicological and nutritional significance (antimony, cadmium, copper, lead, selenium, and zinc), were determined based on analyses from extensive collaborations. Reference values for 12 elements (aluminium, arsenic, barium, calcium, cobalt, iron, magnesium, manganese, silver, sodium, sulfur and vanadium) were also given. Received: 8 February 1996/Accepted: 4 April 1996     

Dispersion of Nanoparticle Clusters by Ball Milling

The full and complete dispersion of nanoparticles is critical to enabling industry to formulate products which exploit the properties of such materials and hence realize the full economic value of such products.

Ball milling is conventionally used for the comminution of particle slurries and, of the various wet milling techniques, is the most effective in producing fine particle sizes. Here we consider the use of a ball mill (also referred to as a stirred media mill) for the dispersion of a slurry of nanoparticle aggregates and compare its performance to a typical rotor‐stator device commonly used by industry. The slurry is an aqueous dispersion of Aerosil 200 V that has a primary particle size of about 12 nm and comes as a dry powder. On dispersion in water it forms large aggregates which are difficult to fully disperse. Aerosil is readily available in quantity and is used in a number of industrially relevant applications and so is an ideal test material for such trials.

A lab scale Fryma Co‐Ball mill (0.5 L volume) is used and the effects of bead fill (40–70%), flow rate (0.1–1 kg/min) and rotor speed (7.5–18 m/s) are investigated. Specific energy is the most effective ways to correlate performance to particle size suggesting that residence time (i.e., flow rate) is the most important process parameter. Lower rotor speeds are also shown to be more energy efficient. The correlations show that the ball mill provides a significant improvement in dispersion (d[3,2]=0.61 µm) over the conventional rotor–stator device.     

Valorization of Kraft Pulp and Paper Mill Slaker Grits and Biomass Fly Ash as Fillers in a Commercial Screed Mortar Formulation

Slaker grits (SG) and biomass fly ash (BFA), two waste streams generated in the pulp and paper industry, are commonly disposed of in landfills, a practice with a high economic and environmental burden. In this work, their individual valorization as fillers in a commercial screed mortar formulation was evaluated in order to achieve a more sustainable management practice. The waste streams were characterized in terms of true density, particle size and morphology, and chemical and mineralogical composition. The influence of their incorporation amount (5.0, 7.5, and 10.0 wt.% of the total solids) and pre-treatment (sieving and grinding) on the fresh (workability) and hardened state (density, water absorption by capillarity, and flexural and compressive strength) properties of the mortars were assessed. The results show that the addition of 10.0 wt.% of the SG after milling and sieving (<75 µm) and 7.5 wt.% of BFA in the as-received condition, or up to 10.0 wt.% after grinding and sieving (<63 µm), allowed for the production of mortar samples with properties within the recommended specifications and that were resistant to 25 consecutive freeze-thaw cycles. This waste valorization route could represent an economic benefit of up to 8.85 €/t_mortar and 2.87 €/t_mortar for mortar, and pulp and paper companies, respectively.     

Effects of ball-to-powder diameter ratio and powder particle shape on EDEM simulation in a planetary ball mill

The effects of the ball-to-powder diameter ratio (BPDR) and the shape of the powder particles on EDEM simulation results and time in the planetary ball mill was investigated. BPDR was varied from 1 to 40/3 by changing the powder particle diameter from 8 to 0.6 ?mm. The size and shape of the powder particles do not give a significant change in both the ball motion pattern and simulation results when BPDR is over 20/3. It can be assumed that the kinetic energy of the ball has nothing to do with the size and shape of the powder particle. The simulation time and data size increase exponentially as BPDR increases. The effect of change of the powder particle shape on the calculated data size is not significant, but the more complicated its shape, the longer the simulation time, which is linearly related to the number of spheres composing a particle.     

Ball Milling Pretreatment of Oil Palm Biomass for Enhancing Enzymatic Hydrolysis

Oil palm biomass, namely empty fruit bunch and frond fiber, were pretreated using a planetary ball mill. Particle sizes and crystallinity index values of the oil palm biomass were significantly reduced with extended ball mill processing time. The treatment efficiency was evaluated by the generation of glucose, xylose, and total sugar conversion yields from the pretreatment process compared to the amount of sugars from raw materials. Glucose and xylose contents were determined using high-performance liquid chromatography. An increasing trend in glucose and xylose yield as well as total sugar conversion yield was observed with decreasing particle size and crystallinity index. Oil palm frond fiber exhibited the best material yields using ball milling pretreatment with generated glucose, xylose, and total sugar conversion yields of 87.0, 81.6, and 85.4 %, respectively. In contrast, oil palm empty fruit bunch afforded glucose and xylose of 70.0 and 82.3 %, respectively. The results obtained in this study showed that ball mill-treated oil palm biomass is a suitable pretreatment method for high conversion of glucose and xylose.     

The effect of soapstock on the cement raw mix grindability

The aim of this work is to investigate the possibility of using industrial wastes as new grinding aids in cement industry. Two samples of Soapstock from different oils were used (Sunflower Oil (SO), Corn Oil (CO)). For this purpose, one reference sample was produced without using any admixture and another one using reference grinding aids (Triethanolamine TEA).The raw mixes were characterized via differential scanning calorimetry (DSC), FT-IR technique, chemical analysis by X-ray florecence (XRF), X-ray powder diffraction (XRD), and mineral composition by Bouge equation and determination of free calcium oxide (CaO_f) for clinker. Grindability was determined according to PSD and resides on sieve 90 μm.In all cases the addition of grinding aids resulted in the improvement of grindability (fact that was attributed to the additive ability not only to reduce resistance to combination, but also to prevent agglomeration and powder coatings of ball and mill), and the clinker produced by this admixture was not effective.     

A High‐Throughput Method for Determining the Stability of Pigment Dispersions

Summary: An approach for the high‐throughput preparation and characterisation of aqueous pigment dispersions is described and evaluated. The use of ultrasonication as a rapid technique for dispersing pigments using polymeric dispersants was developed. The results are comparable to those obtained using time‐intensive conventional high‐energy ball mill processing. The quality of the pigment dispersion was evaluated in a high‐throughput fashion using digital image analysis and the results correlated with particle sizes, determined by photo‐correlation spectroscopy.

Cuvettes containing dispersions of varying particle size.     

超细煤粉吸附苯胺机理研究

采用筛分和高能球磨得到不同粒度煤粉,进行吸附试验研究。结果表明，粒度较大的四种煤粉对苯胺的吸附符合Lagergren一级吸附速率方程，较小的三种超细煤粉对苯胺的吸附符合二级吸附动力学方程。并求出了一级、二级吸附速率常数和有效扩散系数，表明煤粉吸附苯胺的过程由颗粒内扩散控制；煤粉对苯胺的吸附量随煤粉粒径的减小呈指数关系增加。平均粒径d50为9.30μm、4.28μm、和4.82μm煤粉对苯胺的吸附符合Langmuir吸附等温式，单层饱和吸附容量为109.05×10－3、246.31×10－3和90.91×10－3。超细煤粉对苯胺的吸附性能量明显好于其他煤粉。     

Characterizing ablation and aerosol generation during elemental fractionation on absorption modified lithium tetraborate glasses using LA-ICP-MS

The influence of sample matrix composition, absorption behavior and laser aerosol particle size distribution on elemental fractionation in laser ablation inductively coupled plasma mass spectrometry was studied for nanosecond laser ablation at a wavelength of 266 nm. To this end, lithium tetraborate glass samples with different iron oxide contents and trace amounts of a group of 11 elements were prepared synthetically. The samples were characterized in terms of optical absorbance, melting points, trace element concentrations and homogeneity. UV/VIS spectra showed that sample absorption rises with increasing Fe₂O₃ content. Crater depths and time-dependent particle size distributions were measured, and ablated and transported sample volumes were estimated. Furthermore, the laser aerosol was filtered using a particle separation device and transient ICP-MS signals were acquired with and without filtering the aerosol. The results demonstrate that the amount of ablated sample is related to the absorption coefficient of the sample and therefore to the optical penetration depth of the laser beam into the sample. The higher energy densities resulting from the shorter penetration depths result in smaller average particle sizes for highly absorbing samples, which allows more efficient transport to and atomization and excitation of the ablated material within the ICP. The particle size distribution changes continuously with ablation time, and larger particle fractions occur mainly at the beginning of the ablation, which leads to particle-related fractionation processes at the beginning of the transient signal. Exceeding a critical depth to diameter ratio, laser-related elemental fractionation processes occur. Changes in the volatile to non-volatile element intensity ratio after the aerosol is filtered indicate that particle size-related enrichment processes contribute to elemental fractionation.     

Sieving of sediments for subsequent analysis of metal pollution: results of a German interlaboratory study

An interlaboratory study was carried out to get information on repeatability and reproducibility of sieving, and how sieving influences the variability of analytical measurements. Thirteen laboratories took part, sieving three marine sediment samples to get particle size fractions (<20/>20 m; <63/>63 m), and determine their percent by weight. Repeatabilities between 2 and 13% and reproducibilities between 25 and 75% were obtained. Differences in the sieving procedures applied by the participants may be proposed as a reason for the high variability in the results. The determination of metals revealed that they accumulated in the below 20 m fraction. These findings support the common practice in German sediment monitoring programmes of using the <20 m fraction of sediments for metal analysis. The reproducibilities of the analyses of metals in sediments were between 5 and 15%, and indicate a significant influence of sieving on the results.     

中国海大陆架沉积物超细标准物质系列研制

5个中国海大陆架沉积物标准物质的原样分别取自东海和南海,样品风干后,先经球磨制备成200目的均匀粉体,再用气流磨进一步加工成超细粒度的均匀样品.采用激光粒度仪检测了样品的粒度分布,5个样品的平均粒度均小于4 μm(约800目).采用高精度的XRF检验了样品的均匀性并以高灵敏度的ICP-AES、ICP-MS相配合确定了其最小取样量(5 mg).有12个实验室参加了合作定值研究,定值组分均为60个,其中MSCS-1,2分别有50和51个组分定为标准值,MSCS-3,4,5有52个组分定为标准值.全组分百分总和分别为99.9%, 99.9%, 100.4%, 100.1%和99.7%.     

Design and evaluation of a new Peltier-cooled laser ablation cell with on-sample temperature control

A new custom-built Peltier-cooled laser ablation cell is described. The proposed cryogenic cell combines a small internal volume (20 cm³) with a unique and reliable on-sample temperature control. The use of a flexible temperature sensor, directly located on the sample surface, ensures a rigorous sample temperature control throughout the entire analysis time and allows instant response to any possible fluctuation. In this way sample integrity and, therefore, reproducibility can be guaranteed during the ablation. The refrigeration of the proposed cryogenic cell combines an internal refrigeration system, controlled by a sensitive thermocouple, with an external refrigeration system. Cooling of the sample is directly carried out by 8 small (1 cm × 1 cm) Peltier elements placed in a circular arrangement in the base of the cell. These Peltier elements are located below a copper plate where the sample is placed. Due to the small size of the cooling electronics and their circular allocation it was possible to maintain a peephole under the sample for illumination allowing a much better visualization of the sample, a factor especially important when working with structurally complex tissue sections. The analytical performance of the cryogenic cell was studied using a glass reference material (SRM NIST 612) at room temperature and at −20 °C. The proposed cell design shows a reasonable signal washout (signal decay within less than 10 s to background level), high sensitivity and good signal stability (in the range 6.6–11.7%). Furthermore, high precision (0.4–2.6%) and accuracy (0.3–3.9%) in the isotope ratio measurements were also observed operating the cell both at room temperature and at −20 °C. Finally, experimental results obtained for the cell application to qualitative elemental imaging of structurally complex tissue samples (e.g. eye sections from a native frozen porcine eye and fresh flower leaves) demonstrate that working in cryogenic conditions is critical in such type of direct sample analysis.     

Influence of processing technique on morphology and mechanical properties of PVC nanocomposites

This study aims to compare the influence of processing techniques and procedures on the morphology and mechanical properties of polyvinyl chloride (PVC) nanocomposites. PVC nanocomposites with 5 phr montmorillonite (MMT) clay were prepared on a two-roll mill or in a microcompounder, both were either processed once or via a masterbatch containing 20 phr MMT. The MMT was treated with non-ionic surfactants and analysed by thermo gravimetric analysis and X-ray diffraction prior to being added. The final composites were analysed and tested using X-ray diffraction, scanning and transmission electron microscopy (SEM/TEM), tensile test, and Charpy impact test. The dispersion was found to be best in the roll milled samples prepared via the masterbatch and the elongation at break and impact strength was also better for the roll milled samples. E-modulus and tensile strength, on the other hand, were significantly better for the microcompounded samples despite the larger particle size. This can be explained by a higher degree of orientation in these samples. Finally, it must be stated that the change in properties are not satisfactory. Although we see an increase in E-modulus, the decreased impact properties are not acceptable. The main reason for this is the lack of compatibility between the clay particles as observed by high resolution SEM.