Phosphate rocks (PRs) play a crucial role in ensuring the availability of phosphorous for the world’s food needs. PRs are used to manufacture phosphoric acid in the wet process as well as P-fertilizers. The chemical and mineralogical compositions of PRs from Djebel Onk (Algeria), Khneifiss (Syria), Negev (Israel), Bou Craa (Morocco), and Khouribga (Morocco) are discussed in this study. PRs were characterized by inductively coupled plasma optical emission spectrometry (ICP-OES), cold vapor atomic absorption spectrometry (CVAAS), ion chromatography (IC), and X-ray diffraction (XRD), as well as gravimetric and potentiometric methods. All PRs were mainly composed of CaO, P₂O₅, SiO₂, F, SO₃, Na₂O, MgO, Al₂O₃, Fe₂O₃, SrO, and K₂O at the level of wt.%. The P₂O₅ content accounted for 28.7–31.2%, which indicates that these are beneficial rocks to a marketable product. The degree of PR purity expressed by the minor elements ratio index (MER index) varied from 2.46% to 10.4%, and the CaO/P₂O₅ weight ratio from 1.6 to 1.9. In addition, the occurrence of trace elements such as As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Ti, V, U, and Zn, as well as Cr(VI) and Cl ions at the level of mg∙kg⁻¹ was found. Since PRs will be used to produce P-fertilizers, their composition was compared with the regulatory parameters set up by EU Regulation 2019/1009 related to the heavy metals (As, Cd, Pb, Ni, Hg, Cu, Zn) and Cr(VI) contents in inorganic fertilizers. The heavy metals and Cr(VI) content in all PRs did not exceed the limit values. XRD analysis revealed that fluorapatite, hydroxyapatite, carbonate fluorapatite, and carbonate hydroxyapatite were the dominant minerals. The accuracy and precision of the used methods were evaluated by analysis of standard reference materials (SRM) for Western Phosphate Rock (NIST 694). The recovery was 85.3% for U and 109% for K₂O, and the RSD ranged from 0.67% to 12.8%.

Intensive research has been conducted for many years to develop environmentally friendly techniques for plant cultivation that optimize the fertilization process. One of the most promising areas within the fertilizer industry is using microbiologically enriched fertilizers, which incorporate beneficial bacteria or fungi. Biofertilizers are the focus of studies on both their production technologies and their effects on crop growth and yield, presenting a potential alternative to conventional mineral fertilizers. The prolonged and improper use of mineral fertilizers, along with inadequate plant protection, a lack of organic fertilization, and poor crop rotation practices, negatively impact soil health, disrupting microbial populations and ultimately diminishing yield quality and quantity. Microorganisms, particularly specific groups known as plant growth -promoting rhizobacteria (PGPR) and beneficial fungi, are estimated to make up 85% of the total soil biomass and play a crucial role in soil fertility by mineralizing organic matter, suppressing pests and pathogens, forming humus, and maintaining proper soil structure. They also provide optimal conditions for plant growth. Soil microorganisms can be categorized as either autochthonous, naturally present in the soil, or zymogenic, which develop when easily assimilable organic matter is added. Key microorganisms such as Micrococcus, Bacillus, Azotobacter, and nitrogen-fixing bacteria like Rhizobium and Bradyrhizobium significantly contribute to soil health and plant growth. Microbially enhanced fertilizers not only supply essential macro- and micronutrients but also improve soil quality, enhance nutrient use efficiency, protect plants against pathogens, and restore natural soil fertility, fostering a balanced biological environment for sustainable agriculture.

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

The presence of cadmium (Cd) in wet phosphoric acid (WPA), a key intermediate in fertilizer production, poses a significant environmental and health risk due to the potential release of hazardous impurities throughout the fertilizer value chain. As global fertilizer demand intensifies, reducing Cd emissions has become a priority for sustainable production with regulatory compliance. This study evaluates the efficiency of sulfonic acid functionalized resins for the selective removal of Cd(II) ions from industrial WPA, aiming to support cleaner production practices and reduce the environmental footprint of the fertilizer industry. A series of batch experiments was conducted to assess the selectivity, capacity, and operational feasibility of selected cation exchangers under conditions representative of industrial operations. The adsorption process followed pseudo-second-order kinetics and the Langmuir isotherm model, with maximum monolayer capacities of 123.0 mg/g for K1131 S and 173.5 mg/g for K1461. Thermodynamic analysis confirmed that the process is spontaneous and endothermic, while surface characterization (SEM-EDX, XPS, FTIR-ATR) supported the proposed adsorption mechanisms. The results demonstrate that targeted Cd removal at the WPA purification stage significantly reduces the Cd load in downstream fertilizer products and minimizes the risk of soil and groundwater contamination. Overall, the findings indicate that ion exchange processes provide an effective strategy for improving WPA quality, thereby enabling the production of P-fertilizers that meet environmental and quality requirements.

The spent Ni catalyst from the 2nd stage steam reforming and the catalyst previously leached with 3 mol/L HCl were sequential extd. to det. the content of Ni, Co, Cd, Cr, Pb and Mn and to det. the form in which they occur. The metal content in the solns. was detd. by atomic absorption spectrometry (FAAS or GFAAS), and in the catalysts by Xray diffraction (XRD) and X-ray photoelectron spectrometry (XPS). Sequential extn. allowed to ext. significant amts. of Ni contained in the catalyst. Leaching of the catalyst with 3 mol/L HCl led to a redn. in the total content of all tested elements in the material. The highest degree of leaching was found for Ni (98.4%), and the lowest for Pb (20.7%) and Cd (17.1%).