Non Destructive Methods (XRF and XRD) For Estimation of Impure Carbon and Heavy Metals in Printer Toner Ink Powder

Air pollution constitutes the largest among all of the environmental risks. Dust and soot fragments forms components of air particulates, which are released into the air as extremely small particles or liquid droplets. The basis of this research is to characterize toner ink powder and wood soot samples and the detection of metallic pollutants in wood soot (WS) and printer toner ink (PIS) for their physicochemical properties (pH, conductivity, bulk density and moisture content) and instrumental analysis using scanning electron microscopy (SEM) and Fourier Transform Infrared (FTIR). Two nondestructive analytical techniques; Dispersive X-ray Fluorescence Spectrometry (ED-XRF) and X-ray Diffraction (XRD) were adopted for heavy metals (elemental) composition and mineralogy respectively. The pH of printer ink and wood soot shows higher pH value which indicates that they are alkaline. Low conductivity values were reported with low moisture, indicating easy fragmentation and spreading. The bulk density values for samples shows that the soot can be easily spread by air current to the environment. The EDS analysis indicates that the soot particles to be composed of primarily impure carbon, thus pointing at potential organic pollutants. The IR spectra show characteristics signals at 749.2 cm -1 , 745.5 cm -1 , 738.0 cm -1 and 745.5 cm -1 for wood soot and printer ink which correspond to C-H of aromatic group, 1703.4 cm -1 , 1699.7 cm -1 . The XRF analysis reveals high concentration of Chromium and other toxic metals. The mineralogical components of the soot and printer ink samples revealed the presence of associated minerals. Generally, levels of toxic metal exceed the permissible legislative limit for air samples.


Introduction
According to the World Health organization [1], air pollution constitutes the largest among all of the environmental risks: 3 million annual deaths are associated with outdoor air pollution exposure. In 2012 alone, 11.6 percent of global deaths equivalent to 6.5 million deaths were outdoor air pollution-related.

Toner Powder
Toners are complex mixtures with a particle size of approximately 8-12 μm [2], polymer-based powder, widely used in laser printers, photocopiers and fax machines, to form texts and images on the paper by electrophotographic technology. The conventional toner are produced from: styrene-acrylate copolymer and (ii) polyester resin or (iii) combination of styrene-acrylate and polyester. Hence, the major components of toners are polymers, resins, pigments or dyes, iron oxide, amorphous silica, charge control agents, paraffin wax, surfactants and other inorganic/organic additives [2]. As for the black toner, carbon black is mainly used. Important properties of carbon black are their dispersibility in resin in hot melt mixing and their tendency to charge either positive or negative.
Other than carbon black, magnetite is often used in toners to impart magnetic properties to the toner. Some charge control additives such as nigrosine are good black pigments, and their use in a toner can lead to reduction or elimination of the carbon black. Generally, a toner comprises of a binder resin (toner resin), a colorant, a magnetic oxide, a charge control agent and other additives, such as small amount of one or more additives, usually added to adjust the performance of toner in various aspects, including flow control, charge control, cleaning, conductivity control and decrease humidity sensitivity. Surface additives such as fumed silicas and titanias are added to the surface of the toner particles to improve flow characteristics and to prevent agglomeration [3]. In this present study, we report an insight into the available impure carbon and other pollutants in physicochemically characterized toner powder used as printer ink. Characterization of soot was carried out using the X-Ray Fluorescence (XRF) spectrometry, X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Fourier Transform Infra-red (FTIR) Spectroscopic techniques.

Materials and Methods
Non-destructive analytical techniques were adopted in the chemical and physicochemical characterization adopted in this studies. The instruments employed for this research work include, energy dispersive x-ray florescence spectrometer (Mini PAL4), scanning electron microscopy (Q150R), X-Ray Diffraction Instrument (X-SUPREME8000) and Fourier Transform Infra-Red (Agilent tech.Cary630).
Sampling: Printer ink (PIS) was obtained from various printing press and ink refilling points within business center of Bukuru metropolis, Jos Nigeria. Reported sample handling method [4] was adopted. Samples from the same sources were screened, harmonized and stored for analysis. High analytical grade purity chemical reagents and distilled water were used throughout the experiments.
Physiochemical Parameters Toner Ink: The physiochemical parameters of toner ink samples such as pH, conductivity, bulk density and moisture content were carried out using standard laboratory procedures [4].

Characterization of Samples
The characterization method reported by the National Metallurgical Development Centre; NMDC Jos, Nigeria was adopted with slight modification in mass-volume measurements.
Elemental and chemical composition of toner powder was based on XRF analysis. The Scanning Electron Microscopy (SEM) was performed to examine the surface morphology, X-ray powder diffraction is most widely used for the identification of unknown crystalline materials (e.g. minerals, inorganic compounds), crystalline sizes and diffraction pattern. Results are presented as peak positions at 2Ɵ and X-ray counts (intensity) in the form of a table. The crystalline size was computed using the Debye-Scherrer equation given as Eqn. 1 D = Kλ (1) βCosƟ where D is the Crysalline size, K is Scherrer Constant with value 0.9, λ is the wavelength of X-ray (1.540598), β is full width at half maximum and Ɵ is the differential angle [5]. The functional groups present in the soot and printer ink samples were investigated using the Fourier Transform Infrared Spectrometer.

Visual Inspection of Samples
Plate 1 is pictorial representation of printer toner ink powder (a) compared with wood soot (b). Apparent colour of samples were examined with naked eye and were found to be fine black particles, chiefly composed of carbon, they are extremely tiny about 2.5 micro meters or smaller in diameter. It is irritating to the eyes, nose and throat, and it's odor may be nauseating. Due to its color and texture, soot tends to darken or stain surfaces. It stains ventilations, walls, ceiling, floors, clothes, and even skin. It is slightly sticky and tends to cling to surfaces. It was reported that soot is a powdery mass of fine black particles [6]. Table 1 presents the physiochemical parameters such as pH, conductivity, moisture content and bulk density of kerosene based soot, diesel based soot, printer ink and wood soot used as the control experiment. pH -Results in Table 1 shows that the pH range for printer ink and wood soot falls within the alkaline range, for printer ink which is 8.47 and for wood soot which is 7.51. It is an indication that trace metals are present in the samples.

Physiochemical Parameters of Soot Samples and Printer Ink
Conductivity -printer ink and wood soot are low (0.00-0.78). This is an indication that the compound of the samples are mostly covalent with high carbon content [4].
Moisture Content-The results obtained in this analysis indicate the level of clumsiness or ease of dissociation of the soot samples. Low moisture content could also be linked to high persistence and low microbial action (degradation) [7].
Bulk Density -All the values in this analysis shows values of less than1. This is an indication that the soot can be easily spread by air current to the environment [4].

SEM Characterization of Toner Powder and Wood Soot
The morphology of printer ink and wood soot was performed and their respective images displayed as plate 2. Surface morphology of the kerosene based soot, diesel based soot, printer ink and wood soot were examined using the scanning electron microscopy. Several grains with irregular sizes and shapes were observed. The printer ink particles are extremely small. The SEM image of the printer ink show particles of Carbon which are chain-like agglomerations Energy dispersive spectroscopy (EDS) of printer ink is presented in Figure 1. The spectra show high percentage weight of Carbon and Oxygen. The composition of the printer ink aggregates from the EDS analysis indicates the sample to consist of about 57.62% weight of Carbon, 31.44% weight of Oxygen, 8.64% weight of Nitrogen, 1.29% weight of Silicon, 0.37% weight of Sulfur, 0.33% weight of Phosphorus, and 0.31% of Aluminium. The wood soot consists of 66.26% Carbon, 25.86% Oxygen and 5.25% Nitrogen. From the result, the percentage weight of Carbon in wood soot is higher than that of the printer ink. This may be the reason why soot is simply in a quasi-graphic form of nearly pure elemental carbon that is distinguished by its very low quantities of extractable organic compounds and total inorganics [8].

Morphology of Wood Soot
The SEM micrograph of wood soot is presented in plate 2. The surface morphology of the wood soot through the use of scanning electron microscopy shows compact aggregates that are irregular in shapes. There are several grains with what looks like carbon. Energy dispersive spectroscopy (EDS) of wood soot is presented in Figure 2. The spectrum shows the presence of Carbon and Oxygen as the combustion product of wood. The composition of the soot aggregates from the EDS analysis indicates the soot to consist of about 66.26% weight carbon, 25.86% weight oxygen, 5.59% weight Nitrogen, 1.01% weight Chlorine, 0.56% weight Sulfur, 0.15% weight Aluminium, 0.14% weight Sodium, 0.12% weight Silicon and 0.12% weight Phosphorus. The results show that wood soot composed mainly of Carbon and Oxygen with a low level percentage of Nitrogen, Chlorine, Sulfur, Magnesium, Aluminium, Sodium, Silicon and Phosphorus.

Fourier Transform Infra-red Results of Printer Ink and Wood Soot Samples
The quantitative and functional groups of Printer ink powder and wood soot were determined by FTIR technique. This chemical analysis revealed various spectral characteristics for each sample as presented in Figures 3 (a) and (b) respectively. The peak at 693.3cm -1 , 1446.2cm -1 , 1722.0cm -1 , 2914.8cm -1 and 3022.9cm -1 in Printer Ink toner (PIS) comes mainly from C-Cl stretch in alky halides, C-H bend in alkanes, C=O stretch in esters, saturated aliphatic, C-H stretch alkanes and C-H aromatic respectively. The 29.22.2cm -1 , 1036.2cm -1 and 1110.7cm -1 for WS are also attributed to C-H stretch alkanes, C-N stretch alcohols carboxylic acid, esters, ethers respectively. In a published research [9], the extractable material of young soot obtained in the inception region of an ethylene premixed flame was chemically characterized using FTIR analyses. The results indicated that the extractable fraction of the soot demonstrated not only aromatic but also aliphatic characteristics. PAHs are a group of semi-volatile organic compounds composed of 2 or more aromatic rings, generated during incomplete combustion of organic matter. During this process molecules and radical fragment are combined, thus creating these substance [10]. These compounds are major environmental pollutants because they are considered to be potentially carcinogenic and mutagenic, hence considered "air quality markers" in terms of the health risks their presence represents [11]. In the presence of light, amines released in the liquid or gaseous form react with atmospheric oxidants including oxidized Nitrogen compounds (photo-oxidation). As a result, new compounds are formed such as nitrosamines, nitraamines and amides. The formation of nitrosamines is dangerous because these substances are toxic and carcinogenic even at very low concentrations [12]. Formaldehyde, one of the most abundant carbonyls in air, has been classified as a human carcinogen by the International Agency for Research on Cancer (IARC) due to its carcinogenicity [13]. The peak at 1543.1cm -1 and 1509.6cm -1 for DES and DVS respectively are attributed to N-O asymmetric stretch in nitro compound, are not present in wood soot. Nitro compounds are group of the organic substances containing one or more nitro (-NO 2 ) groups within their aromatic ring or aliphatic chain. They are characterized by, especially those aromatic characters high toxicity [14], carcinogenicity [15] resistance to degradation and tendency to accumulate in the environment.

XRF Characterization of Toner Printer Ink Powder and Wood Soot
The comparative study of elements in printer ink and wood soot were carried out. This chemical characterization of the samples to determine the elemental composition using energy dispersive X-ray fluorescence spectrometer (ED-XFR) revealed the results presented in Table 4. The XRF spectra for samples and printer ink are presented in  and bromine but no value in printer ink. Very high value of Chromium was detected in printer ink but wood soot presents no value for chromium. Manganese concentrations as recorded from the analyses are generally high. Although manganese is an essential nutrient, exposure to high levels via inhalation or ingestion may cause some adverse health effects. It has been suggested that these adverse health effects, especially neurologic effects, are occurring on "continuous of dysfunction' that is dose-related [16]. In other words, mild or unnoticeable effects may be caused by law, but physiologically excessive, amounts of manganese, and these exposure level or duration of exposure increases. Chronic exposure to manganese at very high levels results in permanent neurological damage, chronic exposure to much lower levels of manganese (as with occupational exposures) has been linked to deficits in the ability to perform rapid hand movements and some loss of coordination and balance, along with an increase in reporting mild symptoms such as forgetfulness, anxiety, or insomnia [17].

XRD Characterization of Printer Ink Toner Powder and Wood Soot Samples
Tables 5 and Figure 5 presents the crystallographic parameters for printer ink and wood soot analyzed, using Xray diffraction technique.

Mineralogy of Printer Ink
The mineralogical component of printer ink was carried out by X-ray diffraction technique. The main minerals found in the printer ink sample were magnetite and magnesite respectively. With each of this compound having a phase information from the XRD pattern. The result for this shows that 2Ɵ values for magnetite in printer ink produce high intensities at 35.439 and 62.546 regions respectively. This like other compounds present from XRD analysis shows that broadening of reflections beyond (25%) intensity due to instrumental factors is attributed to crystalline size effects. Magnetite with the chemical formula Fe 24 O 32 has cubic crystal system. Magnetite is discussed in regards to its potential applications in environmental engineering, biomedical/medical, microfluidic, and mechano-electrical fields [18]. Environmental, chemical and biological engineers consider magnetite nanoparticles to be used effectively in environmental contaminant removal and cell separation. Small amount of magnetite are used as a toner in electrophotography, as a micro-nutrients in fertilizers, as a pigment in paints and as an aggregate in high density concretes.
Magnesite is a magnesium carbonate mineral with a chemical fomular Mg 6 C 6 O 18 . It is named after the presence of magnesium in its composition. As observed in this research magnesite as one of the component of XRD characterization of printer ink reveals that the 2Ɵ values shows high intensity at 32.660 and 43.005 regions, respectively. This means that broadening of reflections beyond 25% intensity due to instrumental factors is predominantly attributed to crystallite size effects. The crystal system of magnesite is hexagonal. Magnesite usually forms during the alteration of magnesium-rich rocks or carbonate rocks by metamorphism or chemical weathering. Magnesite is used to produce Magnesium Oxide (MgO), which serves as a refractory material for the steel industry and as a raw material for the chemical industry. small amounts of magnesite are also used as a gem and lapidary material [19].

Mineralogy of Wood Soot
The mineralogical component of wood soot sample was carried out by X-ray diffraction technique. The main minerals found in the sample were Calcite, Sylvite and Quartz. Each of these compounds have a phase information from XRD pattern. The chemical analysis of the Calcite in wood soot sample reveal that high intensity observed for 2Ɵ value is only at 29.390. Broadening of reflection attributed to crystallite size is less. Calcite is widely distributed in earth's crust; it appears most commonly within sedimentary rocks, where it occurs as the principal mineral of limestone, and as a natural cementing agent in many siliceous sand, stone and shale units that were deposited under marine conditions. Calcite also dominates some metamorphic rocks such as marble and calcareous gneiss; occurs widely in hydrothermal system, where it forms extensive vein networks; and is common in some unusual carbonaterich igneous rocks such as carbonatites. Calcite is used as an acid neutralizer in the chemical industry in areas where streams are plagued with acid mine drainage, crushed limestone is dispensed into the streams to neutralize their waters [20].
Quartz also reveals a single high intensity at 2Ɵ value 26.624, other intensities reveals lower values below 25% intensity. Broadening of these reflections beyond that due to instrumental factors is attributed to crystallite size effects. Quartz is one of the most famous mineral on the earth, it occurs in essentially all mineral environments, and is the crucial constituent of many rocks. It is likewise the maximum varied of all minerals, taking place in all distinct bureaucracy, habits and colouring. Quartz is highly resistant to both mechanical and chemical weathering. This durability makes it the dominant mineral of mountain tops and the primary constituent of sea side, river, and wilderness sand. It is ubiquitous, ample and durable. Mineral deposits are determined at some stage in the world. The weathering of any quartz bearing rocks creates sand: igneous, sedimentary or metamorphic rock rocks. It is a continuous cycle of rocks formation and erosion that started with the earth's formation and continues today. Quartz is used in a great variety of products and the term "Quartz sand in its finest form, as micro-silica is used as an essential raw material for the glass and foundry casting industries, as well as in other industries such as ceramics, chemical manufacture and for water filtration purposes. This result revealed that the 2Ɵ values for Sylvite between 28.314 and 40.472 shows high intensities. This means that broadening of reflections beyond 25% due to instrumental factors is predominant for Sylvite in wood soot sample and this is attributed to crystallite size effects. Sylvite is an economically important mineral and is extensively mined, though it is rarely presented in mineral collections as attractive specimens. It is the most significant form of potash, or potassium bearing compounds. Sylvite is the main source of potash, which is an important ingredient in fertilizers. It has other important industrial uses, including aluminium recycling, metal electroplating, and in oil drilling fluids.

Conclusion
Highlights of the studies revealed high concentration of impure carbon in both toner ink powder and wood soot, with crystallographic sizes at the nano range, marking the possibilities of easy fragmentation into air current. The FTIR spectral analysis revealed that aromatic, primary amines, carbonyl, and alkynes were present. These compounds are major environmental pollutants and are considered to be potentially carcinogenic and mutagenic.