Wet Acid Research Articles

Process modelling and techno-economic analysis of anaerobic digestion of sewage sludge integrated with wet oxidation using a gravity pressure vessel and thermal hydrolysis

Anaerobic digestion (AD) of sewage sludge is used to biodegrade sewage sludge into biomethane and digestate. With the addition of thermal processes such as thermal hydrolysis (TH) and wet oxidation (WO), AD biodegradability generally improves. Implementation of additional treatment is challenging due to the limitation in the mass and energy balances. Hence, tools such as process simulation can be utilized to predict the input and output around the process. In addition, an economic analysis needs to be conducted to check the economic feasibility. The techno-economic analysis (TEA), an integrated method to evaluate a process scheme through simulation and subsequent economic analysis, is effective in providing a systematic understanding of economic implications and the feasibility of a process by identifying the bottlenecks and uncertainties that have a significant impact on the technology. TEA of AD, especially incorporating the TH or WO using gravity pressure vessel (GPV) technology, is limited in the literature. A comprehensive TEA of the AD and the pre- and post-treatment schemes can be utilized to determine the most feasible pathway for sludge treatment for implementation in the wastewater industry. In this study, TEA for four different scenarios of AD was conducted using Aspen Plus and economic analysis tools: (1) without any pre- or post-treatment, (2) with TH pre-treatment, (3) with 100 % WO post-treatment, and (4) with 20 % partial wet oxidation (PWO) and acid hydrolysis pre- or post-treatment. A simulation model (GPVM) was developed using Aspen Plus to mimic the GPV reactor. The study outcomes showed that Scenario 3 with 100 % WO post-treatment was the most suitable for processing parameters and sludge treatment cost. The sensitivity analysis concluded that operating cost and plant capacity are the dominant factors that impact the plant feasibility significantly.

The ultramicropore biochar derived from waste distiller’s grains for wet-process phosphoric acid purification: Removal performance and mechanisms of Cr(VI)

Solid waste and heavy metal pollution are long-term and challenging subjects in the field of environmental engineering. In this study, we propose a sustainable approach to “treating waste with waste” by utilizing the ultramicropore biochar derived from solid waste distiller’s grains as a means to remove Cr(VI) from simulated wastewater and wet phosphoric acid. The biochar prepared in this research exhibit extremely high specific surface areas (up to 2973 m2/g) and a well-developed pore structure, resulting in a maximum Cr(VI) adsorption capacity of 426.0 mg/g and over 99% removal efficiency of Cr(VI). Furthermore, the adsorbent can be reused for up to eight cycles without significant reduction in its Cr(VI) adsorption performance. Mechanistic investigations suggest that the exceptional Cr(VI) adsorption capacity can be attributed to the synergistic effect of electrostatic interaction and reduction adsorption. This study offers an alternative approach for the resource utilization of solid waste distiller’s grains, and the prepared biochar holds promise for the removal of Cr(VI) from wastewater and wet-process phosphoric acid.

Evaluation of Chemical Composition and Antimicrobial Activities of Charcoal Obtained from Almond Tree Stem

The emergence of antimicrobial resistance has spurred the search for alternative antimicrobial agents for drug-resistant species. This study aimed to investigate the chemical composition and antimicrobial activity of charcoal obtained from the almond (Terminalia catappa) tree stem, commonly known as fruit in Nigeria. The charcoal was extracted from Terminalia catappa using the earth pit kiln method of carbonization, and its chemical composition was analyzed using the cold extraction method followed by qualitative phytochemical analysis. Mineral analysis was conducted using the wet acid digestion method, followed by spectrophotometric analysis using Atomic Absorption Spectrophotometer (AAS) and Flame Absorption Spectrophotometer (FAS). Additionally, the antimicrobial activities of the charcoal were evaluated against ten (10) clinical isolates using the MIC/TTC and mycelial inhibition concentration method. The results revealed the presence of tannins, alkaloids, steroids, and flavonoids. Mineral analysis showed that K had the highest concentration in the order of K >Na > Ca, while trace element analysis indicated that Fe had the highest concentration in the order of Fe > Cr > Zn >Cu >Mn >Pb. Charcoal demonstrated significant antimicrobial activity against Pseudomonas aeruginosa at a concentration of 200 mg/ml with a minimum inhibition concentration (MIC) value of 50%, as well as against Aspergillus terreus with a growth inhibition value of 64% at a concentration of 100 mg/ml. These findings highlight the potential of Terminalia catappa stem charcoal as a natural antimicrobial agent and a promising source of raw materials for pharmaceutical applications.

Evaluation of Cu, Zn, Fe, and Mn Concentrations in Water, Soil, and Fruit Samples in Sargodha District, Pakistan

This study aimed to assess the concentrations of copper (Cu), zinc (Zn), iron (Fe), and manganese (Mn) in the edible parts of grapefruit and kinnow fruit irrigated with sewage water (SW), tube-well water (TW), and canal water (CW). Preparation of the samples used in the study for metal analysis was carried out via the wet acid digestion method. Atomic absorption spectrometry (AAS) was used for metal determination. According to the results, Cu concentration ranged from 0.152 to 0.754 mg/L in water, 5.254 to 41.659 mg/kg in soil, and 0.128 to 0.864 mg/kg in fruit samples. Zn concentration varied from 0.574 to 2.723 mg/L in water, 17.812 to 112.954 mg/kg in soil, and 2.658 to 42.642 mg/kg in fruit samples. Fe concentration ranged from 0.254 to 1.245 mg/L in water, 10.635 to 48.638 mg/kg in soil, and 1.062 to 7.584 mg/kg in fruit samples. Mn concentration ranged from 0.154 to 0.638 mg/L in water, 51.283 to 183.865 mg/kg in soil, and 0.136 to 1.464 mg/kg in fruit samples. The Pollution Load Index (PLI) indicated that Cu and Mn exceeded a PLI value of one, and Zn had a PLI > 1 only in sewage water-irrigated sites. Bioconcentration Factor (BCF), Enrichment Factor (EF), Daily Intake of Metal (DIM), and Health Risk Index (HRI) values for all metals were within permissible limits, indicating no immediate health risks associated with consuming these fruits.

The Effects of Irrigation with Diverse Wastewater Sources on Heavy Metal Accumulation in Kinnow and Grapefruit Samples and Health Risks from Consumption

This study aimed to assess the concentrations of Pb, Cr, Cd, and Ni in the edible parts of grapefruit and kinnow fruit irrigated with sewage water, tube-well water, and canal water. Preparation of the samples used in the study for metal analysis was carried out by the wet acid digestion method. Atomic absorption spectrometry was used for metal determination. All of the studied metals were more abundant in water, soil, and fruit samples from sites irrigated with sewage water than from those irrigated with tube-well and canal water. The concentrations of Pb were established in the range of 0.047 to 0.175 mg/L in water, 12.652 to 47.863 mg/kg in soil, and 0.023 to 0.124 mg/kg in fruit samples of both varieties. The range of Cr varied from 0.107 to 0.741 mg/L in water, from 1.121 to 5.835 mg/kg in soil, and from 0.054 to 0.784 mg/kg in fruit samples of both varieties. The range of Cd varied from 0.004 to 0.028 mg/L in water, from 1.258 to 4.246 mg/kg in soil, and from 0.012 to 0.131 mg/kg in fruit samples of both varieties. The range of Ni varied from 0.384 to 1.815 mg/L in water, from 5.367 to 18.658 mg/kg in soil, and from 0.028 to 1.475 mg/kg in fruit samples of both varieties. The pollution load index indicated that Pb exceeded a value of 1, while Cd and Ni exceeded 1 only in sewage-water-irrigated sites. The bioconcentration factor, enrichment factor, daily intake of metal, and health risk index values for all metals were below 1, within permissible limits, indicating no immediate health risks associated with consuming these fruits.

Removal of Organic Matter from Tunisian Industrial Phosphoric Acid by Adsorption onto Purified Natural Illite/Kaolinite Clay: Kinetics, Isothermal and Thermodynamic Studies.

This work aims to use a green, economical and efficient adsorbent to remove organic matter from Tunisian industrial wet phosphoric acid (WPA: 52% P2O5). For this purpose, a natural and abundant clay is extracted from the Douiret, Tataouine deposit in southern Tunisia. This clay is being tested for the first time as an adsorbent in WPA medium. The raw clay and purified clay are analysed using standard analytical techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, and BET methods. The results show that the raw clay is a mixture of illite and kaolinite, with other mineral impurities, mainly quartz. Organic matter adsorption tests show that the purified clay exhibits greater effectiveness than raw clay. The parametric study with purified clay indicates that temperature, contact time, and clay dosage strongly influence organic matter adsorption. The highest adsorption occurs at 60 °C after 50 min, reaching 56% with 8 g of purified clay per kg of WPA. Among several recognised models, the pseudo-second-order kinetic model and the Sips isotherm model are the most suitable for modelling the experimental data. This study suggests that Douiret clay can be considered an effective, inexpensive and environmentally friendly adsorbent for eliminating organic matter in industrial phosphoric acid.

Identification and Characterization of Mercury Contamination in Vegetables and Herbs Cultivated on a Commercial Vertical Indoor Farming System with Light-Emitting Diode Lighting: Unveiling an Unusual Food Safety Risk of Some Improperly Manufactured High-Density Agricultural Production Systems.

Artificial grow lights, such as light-emitting diodes (LEDs) and fluorescent grow lights, are commonly used in modern day indoor farming, citing advantages in energy efficiency and a higher controlled environment. However, the use of LEDs poses a risk in mercury contaminations as a result of its production process, specifically LEDs with polyurethane encapsulates that were traditionally produced using mercury resins as a catalyst. A total of 10.0 ppm of mercury was detected in a curly kale sample harvested from an indoor hydroponic vegetable farm, exceeding Singapore Food Regulation's limit of 0.05 ppm. Vegetables, farming inputs, and surface swabs from the affected farm were analyzed using wet acid digestion followed by cold vapor atomic absorption spectroscopy analysis. The investigation found high concentrations of mercury in the LED encapsulant, and the encapsulant material was identified to be polyurethane by Fourier transform infrared spectroscopy and pyrolysis-gas chromatography-mass spectrometry analysis, indicating the source of mercury contamination to be the LED polyurethane encapsulant.

Life cycle assessment of fermentative xylitol production from wheat bran: A comparative evaluation of sulphuric acid and chemical-free wet air oxidation-based pretreatment

Xylitol, a sugar alcohol is a low-calorie sweetener has wide applications in food and pharmaceutical industry and hence considered as a high value premium product. The conventional methods for fermentative xylitol production uses chemicals (acid/alkali) which generates inhibitors affecting fermentation and downstream purification of xylitol. In the present study, wet air oxidation was evaluated as a chemical-free pretreatment option of wheat bran for xylose release which is subsequently fermented to xylitol. Life cycle assessment was used as a tool to compare wet air oxidation with conventional methods like dilute acid pretreatment for valorization of wheat bran, a model agro-industrial remnant. A comparative evaluation of wet air oxidation and dilute acid pretreatment was investigated for fermentative production of xylitol (1 g/L as functional unit) with the aim of identifying the process involved with the lowest environmental impact, while also demonstrating the higher xylose recovery of 13.52 g/L coupled with FO based concentration unit. The inputs and outputs of the process involving energy use, chemicals employed, and emissions produced were evaluated with respect to food and environment perspective. Environmental impacts of wet air oxidation and dilute acid pretreatment with fermentative xylitol production of 6.134 and 1.42 g/L, respectively showed emission results of 1.476 and 5.288 kg CO2 equivalent, respectively. Though, primary energy demand of wet air oxidation was almost found to be equivalent to dilute acid, due to energy penalty for reactor mixing was higher in wet air oxidation. However, energy demand of wet air oxidation-based pretreatment was found to be energy efficient by 30% as compared to dilute acid. Coupling biogas reduces energy demand by 3.5%. The reduction in impacts relevant to food safety namely, marine aquatic and freshwater ecotoxicity potential were found by 74.29% and 84.97% substantially lower in wet air oxidation as compared to dilute acid based xylitol production. The effect of sulphate, as input form of sulphuric acid in dilute acid showed an impact of 3.83 folds higher on human toxicity potential as compared to wet air oxidation pretreatment process.

Electrochemical Hydrogen Sulfide Decomposition Using Proton Conducting Ceramic for Pure Hydrogen Production

Hydrogen sulfide (H2S) is a substance that occurs during the process of processing sulfur, which is abundant in fossil fuels such as oil and natural gas, into high-quality fuel. Due to its high toxicity, it is classified as harmful industrial waste and removal in the process of discharging is essential. Until now, refiners have used the Claus process and the Wet Sulfuric Acid (WSA) process, which reacts hydrogen sulfide with oxygen to release it in the form of water or sulfuric acid. These processes require a huge amount of heat energy and only aim to remove hydrogen sulfide, so they emit hydrogen atoms contained in hydrogen sulfide in the form of water and sulfuric acid. Because hydrogen is an eco-friendly energy source that has recently been in the spotlight, hydrogen sulfide can be a valuable resource if hydrogen can be extracted from hydrogen sulfide. In this study, an electrochemical process that decomposes hydrogen sulfide and obtains hydrogen from hydrogen sulfide, replacing the conventional hydrogen sulfide removal process was proposed. To achieve this goal, thermodynamics of this reaction was analyzed and a solid oxide electrochemical cell based on proton conducting ceramic was fabricated for operating at high temperature and using perovskite structured electrodes. Experiments were then conducted to decompose hydrogen sulfide using fabricated cells and found that about 40 ppm, 100 sccm of hydrogen sulfide was decomposed at 600 oC by applying 0.5 V, 0.57 mA/cm2. Through this, the feasibility of the process was confirmed, and the durability test and regeneration process of the anode electrode were proceeded to solve degradation caused by sulfur deposits. In this study, a process has been proposed to effectively produce hydrogen of high value as an energy source, as well as to remove industrial waste hydrogen sulfide. It is expected that waste disposal and energy source production can be simultaneously produced in a clean and efficient way if cell performance improvement, removal of sulfur poison, and large systemization are applied to oil refiners' processes.

Efficient extraction of impurities from phosphogypsum during crystal regulation of α‐hemihydrate gypsum

AbstractPhosphogypsum (PG) is a solid waste generated during the “wet phosphoric acid process.” The phosphorus (P) impurities and low‐value‐added recycling products seriously constrain PG re‐utilization, which results in its massive accumulation and thus occupies large land areas and poses a severe pollution threat to the environment. In this study, by regulating gypsum crystal and P species in CaCl2–HCl solutions under mild conditions, efficient removal of P impurities (leaching efficiency of 97.78%) and synchronous preparation of high‐strength α‐CaSO4·0.5H2O (α‐HH) (compressive strength of 35.2 MPa) from PG were achieved during the phase transition from CaSO4·2H2O (DH) to α‐HH, which was a reaction of DH dissolution, followed by α‐HH crystallization. The co‐crystalline P was fully released during the dissolution process, which was necessary to efficiently eliminate P impurities. HCl dissolved the released P and transformed them into the protonated specie (H3PO4) with less similarity to SO42−, which prevented the recombination of the released P with gypsum during the crystallization process. Furthermore, α‐HH morphology and size were controlled by seeding in the mixed solutions. The formation of regular large α‐HH crystals with a low‐specific surface area significantly weakened the surface adsorption of P in solutions and further increased the P leaching efficiency. More importantly, the large stumpy α‐HH was identified as high‐strength gypsum with high added value. This work would provide innovative guidance to efficiently remove impurities from gypsum and pioneer a cost‐effective approach for clean and high‐value utilization of industrial gypsum residues.

Process of preparing chloride-free KNS compound fertilizers from phosphogypsum waste using a quaternary phase diagram

Phosphogypsum (PG), commonly known as calcium sulfate, is a waste by-product generated during the production of phosphoric acid by the wet phosphoric acid process (WPA). It is well known that every year the phosphate industries produce a large quantity of PG around the world (i.e., Currently, global production of this waste is estimated at 300 Mt/ year), but the valorization processes of this waste are limited and low valuable. In this study, we investigated the recycling of PG by-product, which can be considered very promising sources of sulfate ions (SO42-) for the manufacturing of chloride-free KNS compound fertilizer based on potassium-ammonium sulfate ([K1−x(NH4)x]2SO4). The primary objective of this study was to develop a methodology for [K1−x(NH4)x]2SO4 synthesis and its separation process using the quaternary phase diagram K+, NH4+ / Cl-, SO42- - H2O at 25 °C. The experiment results show that it is possible to recover relatively pure (NH4)2SO4 from PG to re‐synthesize in presence of KCl the [K1−x(NH4)x]2SO4 phase, whose high quality and purity were confirmed by the combined use of several analytical and characterization techniques such as X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and gamma spectrometry analysis. The thermal decomposition was supplemented by Thermo-Gravimetric Analysis (TGA) coupled with Differential Thermal Analysis (DTA). The main findings of this study may assist in developing methods for valorizing PG waste by converting it into valuable fertilizer products, which are particularly suitable for cultivating chloride-sensitive crops. Thus, total or partial substitution of non-renewable resources by PG not only helps to solve the environmental pollution caused by this waste, but also reduces production costs and improves farm economics.

CATALYSTS AND ADSORBENTS FOR CONVERSION OF NATURAL GAS, FERTILIZERS PRODUCTION, PURIFICATION OF TECHNOLOGICAL LIQUIDS

The work is devoted to investigation of catalysts and adsorbents used in the production of ammonia, methanol, and formaldehyde, hydrogenation of various organic compounds, defluorination of wet phosphoric acid, adsorptive wastewater treatment, and inhibition of combustion chain reactions. Main approaches for the synthesis of adsorption-catalytic systems, governing the composition, structural and textural properties and providing specific functionality, were studied. Those included mechanochemical synthesis and activation, surface modification, precipitation, impregnation, etc. For citation: Kunin A.V., Ilyin A.A., Morozov L.N., Smirnov N.N., Nikiforova T.E., Prozorov D.A., Rumyantsev R.N., Afineevskiy A.V., Borisova O.A., Grishin I.S., Veres K.A., Kurnikova A.A., Gabrin V.A., Gordina N.E. Catalysts and adsorbents for conversion of natural gas, fertilizers production, purification of technological liquids. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 7. P. 132-150. DOI: 10.6060/ivkkt.20236607. 6849j.

Loquat seed starch — Emerging source of non-conventional starch: Structure, properties, and novel applications

Recently, non-conventional sources of starch have attracted attention due to their potential to provide cost-effective alternatives to traditional starch. Among non-conventional starches, loquat (Eriobotrya japonica) seed starch is an emerging source of starch consisting of the amount of starch (nearly 20 %). It could be utilized as a potential ingredient due to its unique structure, functional properties, and novel applications. Interestingly, this starch has similar properties as commercial starches including high amylose content, small granule size, and high viscosity and heat stability, making it an attractive option for various food applications. Therefore, this review mainly covers the fundamental understanding of the valorization of loquat seeds by extracting the starch using different isolation methods, with preferable structural, morphological, and functional properties. Different isolation and modification methods (wet milling, acid, neutral and alkaline) are effectively used to obtain higher amounts of starch are revealed. Moreover, insight into various analytical techniques including scanning electron microscopy, differential scanning calorimetry, and X-ray diffraction used to characterize the molecular structure of the starch are discussed. In addition, the effect of shear rate and temperature on rheological attributes with solubility index, swelling power, and color is revealed. Besides, this starch contains bioactive compounds that have shown a positive impact on the enhancement of the shelf-life of the fruits. Overall, loquat seed starches have the potential to provide sustainable and cost-effective alternatives to traditional starch sources and can lead to novel applications in the food industry. Further research is needed to optimize processing techniques and develop value-added products that can be produced at a large scale. However, there is relatively limited published scientific evidence on the structural and morphological characteristics of loquat seed starch. Thus, in this review, we focused on different isolation techniques of loquat seed starch, its structural and functional characteristics, along with potential applications.

A novel and complete process for iodine extraction and recovery from industrial wet-process phosphoric acid based on chemical oxidation and solvent extraction

Due to their copious availability and broad applicability, iodine recovery from numerous sources, such as byproducts of various industrial processes, has attracted attention. To meet growing market demand for iodine as well as to accomplish long-term management of iodine resources, phosphate rocks and their derivatives were discovered as a possible source of iodine. As phosphoric acid is produced in significant quantities each year more than 20 million tons the extraction of iodine, a byproduct of the wet processing of phosphoric acid, is crucial. This research aims to develop a pre-oxidation and solvent extraction-based method for recovering high purity iodine from wet phosphoric acid (SX). For this purpose, the effects of operating variables, such as: time, acidity, dose of the oxidant, temperature, volume ratio, and the concentration of stripping solution have been studied. Using 30% H2O2 as an oxidant, all the iodides ions present in wet phosphoric acid was converted into elemental iodine. The iodine was then extracted and stripped quantitatively using pure kerosene and 0.02 M sodium sulfite at ratios (O:A) of 1:2 and 1:1, respectively. The resulting iodine precipitate was subjected to several analyses, including iodometric titration, XRD, and ICP-OES, which confirmed its purity to be 99.9%. Finally, a flowchart process for both recovering and reducing the loss of iodine from wet phosphoric acid was developed without interfering with the normal fertilizer production route.

Study on the Phosphogypsum Proportion in Foamed Concrete Based on Concrete Strength and Carbon Emission

The production of concrete will produce a lot of carbon dioxide and pollute the environment. Phosphogypsum is a solid waste generated during wet phosphoric acid treatment, and the use of phosphogypsum blending instead of cement in concrete production can effectively reduce carbon dioxide emissions. Then, experiments were conducted for six concrete groups with different phosphogypsum content as 0%~50% to test the strength in 3 days, 7 days, and 28 days. The results show that as the curing day rise, the compressive strength of concrete increases, meanwhile, with the increment of phosphogypsum content, the 28-day strength decreases significantly. The analysis for the consideration of the balance in carbon emission and the strength evolved, and results could be concluded that although the decrement of 28-day strength as well as the carbon dioxide emissions with the increasing phosphogypsum content in concrete, different trends were found. As the strength and emissions vary, a suggested range of content for phosphogypsum in concrete can be found. Based on these results, the proportion of phosphogypsum in concrete is proposed to achieve the purpose of energy saving and emission reduction and improve the utilization rate of phosphogypsum.

Towards improved conversion of wet waste to jet fuel with atomic layer deposition-coated hydrodeoxygenation catalysts

The conversion of wet waste-derived volatile fatty acids into jet fuel-range hydrocarbons is a promising route for increasing the production of sustainable aviation fuel; however, the cost and moderate alkane selectivity of Pt-based hydrodeoxygenation catalysts present challenges for commercialization. To address this, we used atomic layer deposition to apply TiO2 overcoats to Pt/Al2O3 catalysts and create new interface sites that exhibited 8 times higher site time yield of the desirable n-alkane product than uncoated catalyst. Through TPR/TPD, XPS, CO DRIFTS, and DFT calculations, we found that the increased selectivity of the ALD-coated catalyst was due to the creation of O vacancies at the Pt-TiO2 interface under reducing conditions, resulting in new Ti3+ acid sites near the active metal. Maximum conversion and alkane selectivity during HDO was achieved with an ALD-coated 0.5% wt Pt catalyst, indicating that TiO2 ALD can be used to maximize the utility of precious-metal catalysts.

Surface modification of anhydrous phosphogypsum and its application in isotactic polypropylene

Phosphogypsum (PG) is a by-product of the wet phosphoric acid process, and anhydrous phosphogypsum (APG) prepared by PG calcination and ball milling pretreatment can be useful to prepare polypropylene composites by melt blending to yield polymer materials with improved properties. In this work, the hydrophobic effect of stearic acid (SA) modified APG was investigated by various analytical techniques. To this end, the modified APG was used as a filler for isotactic polypropylene (PP) blending to yield PP/APG composites and study the influence of APG particle size and added amount on the mechanical properties of PP/APG composites. The results showed SA coated on APG surface by chemical adsorption to form a hydrophobic layer. The water contact angle increased from 8.49° to 112.49° before to after modification, respectively. The mechanical properties of PP/APG composites were affected by the particle size and content of APG. Smaller particle size of APG led to better mechanical properties of PP/APG composites. At particle size d50 of APG filler of 2.83 μm and content of 5 wt%, characteristics like the tensile strength, flexural strength, impact strength, and tensile modulus of PP/APG composites reached 37.28 MPa, 47.71 MPa, 6.18 KJ/m2, and 422.3 MPa, respectively. Compared to pure PP, these values increased by 4.66%, 5.4%, 27.68%, and 18.28%, respectively. Smaller particle size of APG was also found more conducive to the increase in APG content within PP/APG composites, as well as reduced production cost of composites. APG prepared from PG after treatment is useful as a filler for PP and other polymer materials, promising for PG resource utilization.

Corrosion inhibition of carbon steel in wet acid gas environment using CORR 11631 A: Weight loss and computational investigations

Corrosion inhibition of carbon steel in wet acid gas environment using CORR 11631 A: Weight loss and computational investigations

Identification and Quantification of the Organic Matter in the Fouling Industrial of Wet Phosphoric Acid Process

The organic matter of rock phosphate has been the subject of numerous studies. The valuation and resolu-tion of some problems, such as fouling, encountered in the industrial production of phosphoric acid are of great interest, and enable better production yields of phosphoric acid. The solid deposits formed in the production of wet process phosphoric acid were characterized and revealed the malladrite, gypsum, trace metals, and the presence of organic matter. The identification of the organic matter was carried out in the fouling samples using FT-IR and Raman spectroscopies. The quantitative determination of the total organic matter content of the fouling samples was performed using the Walkley-Black and calcination methods. The knowledge of the organic matter in the fouling layers allows a better understanding of phenomena in processes.

Structural and Distribution of Impurities in the Fouling in Wet-Process Phosphoric Acid at T = 80°C

In this investigation, the mineral deposits formed in the digestion step in wet phosphoric acid production were studied. The mineralogical characterization of the fouling precipitates obtained at the temperature 80°C from the digestion step in 16-monthly production cycle was carried out. Observing successive layers, based on their colors, allowed us to distinguish fouling layers. Detailed structural aspects, and subsequently, chemical and physical properties of the fouling were determined using complementary analytical and characterization techniques. Particle size fractionation was then used to gain each fouling layer sample homogenized on the micro-scale (63μm). The major elements in the fouling were determined to be silica (Si₂O) and sodium (Na). Some chemical elements of major impurities, as well as traces, K, Al, Mg, Fe, Cu, and Zn, were detected using XRF which cannot appear in their proper solid phases. The obtained solid phases in different fouling layers are principally composed of the malladrite and gypsum minerals. The distribution of impurities into the present structures was investigated. Indeed, the mesh parameters of malladrite in the fouling layers were calculated and compared with those of the pure phase, and a good concordance is obtained. The FT-IR spectra confirm the presence of mallardite and gypsum phases and reveal a supplementary band that has been assigned to C-O vibrations in acids, esters, or ethers. The appearance of this band indicates the possible presence of organic matter within the fouling layer.