THE IMPACT OF DIAMIDE DERIVATIVES OF OXALIC ACID ON FREE RADICAL LIPID OXIDATION IN WHITE RAT BRAIN AND LIVER.

Antioxidants are widely used in medicine due to their ability to bind free radicals - active biomolecules that destroy the genetic apparatus of cells and the structure of their membranes, which makes it possible to reduce the intensity of oxidative processes in the body. In a living organism, free radicals are involved in various processes, but their activity is controlled by antioxidants. The purpose of this work was to conduct a series of studies to identify the antioxidant activity of new synthesized compounds of a series of oxalic acid diamides in the brain and liver tissue of white rats in vivo and in vitro experiments, as well as to determine their potential pharmacological properties. The studies were conducted on outbred white male rats, weighing 180-200 g, kept on a normal diet. After autopsy, the brain and liver were isolated, washed with saline, cleared of blood vessels, and homogenized in Tris-HCl buffer (pH-7.4) (in vitro). The research results showed significant antioxidant activity (AOA) of all compounds with varying effectiveness. The most pronounced activity was demonstrated by compound SV-425 in both brain and liver tissues. Compound SV-427 demonstrated the least activity, with levels in brain tissue and liver tissue. In addition, all physicochemical descriptors of the studied compounds comply with Lipinski's rule of five to identify new molecules for the treatment of oxidative stress. From the data obtained, it can be concluded that the studied compounds have antioxidant properties, helping to protect cells from oxidative stress. This is important for the prevention and treatment of diseases associated with increased levels of free radicals.

Impact of low molecular weight organic acids on heavy metal(loid) desorption in biochar-amended paddy soil.

Low molecular weight organic acids (LMWOAs) are important soil components and play a key role in regulating the geochemical behavior of heavy metal(loid)s. Biochar (BC) is a commonly used amendment that could change LMWOAs in soil. Here, four LMWOAs of oxalic acid (OA), tartaric acid (TA), malic acid (MA), and citric acid (CA) were evaluated for their roles in changing Cd and SB desorption behavior in contaminated soil with (S1-BC) or without BC (S1) produced from Paulownia biowaste. The results showed that OA, TA, MA, and CA reduced soil pH with rising concentrations, and biochar partially offset the pH reduction by LMWOAs. The LMWOAs reduced Cd desorption from the soil at low concentrations but increased Cd desorption at high concentrations, and CA was the most powerful in this regard. The LMWOAs had a similar effect on Sb desorption, and CA was the most effective species of LMWOAs. Adding BC to the soil affects Cd and Sb dynamics by reducing the Cd desorption but increasing Sb desorption from the soil and increasing the distribution coefficient (Kd) values of Cd but lowering the Kd values of Sb. This study helped understand the effects of LMWOAs on the geochemical behavior of Cd and Sb in the presence of biochar, as well as the potential risks of biochar amendment in enhancing Sb desorption from contaminated soil.

Leaching of liquation-feeding furnace dross as a first step for germanium recovery.

OBJECTIVE: Germanium, an important component of electronics, is considered by many global economies as a critical raw material. Therefore, investigating its potential new sources is crucial for prospective technology development. This paper presents the investigation results on the leaching of liquation-feeding furnace dross using sulfuric and oxalic acid solutions. RESULTS: The dross contained mostly zinc (68.0% wt.) but also elevated germanium concentration (0.68% wt.). The influence of temperature, time, initial acid concentration, and liquid-to-solid phase ratio (L:S) was examined. It was found that germanium availability via leaching is limited-maximum leaching yields using aqueous solutions of sulfuric and oxalic acids were 60% (80 °C, 2 h, 15% wt. H2SO4, L:S 25:1) and 57% (80 °C, 3 h, 12.5% wt. H2C2O4, L:S 10:1), respectively.

Ferrioxalate photolysis-assisted green recovery of valuable resources from spent lithium iron phosphate batteries.

Recovering valuable resources from spent cathodes while minimizing secondary waste generation is emerging as an important objective for the future recycling of spent lithium-ion batteries, including lithium iron phosphate (LFP) batteries. This study proposes the use of oxalic acid leaching followed by ferrioxalate photolysis to separate and recover cathode active material elements from spent LFP batteries. The cathode active material can be rapidly dissolved at room temperature using appropriate quantities of oxalic acid and hydrogen peroxide, as determined through thermodynamic calculations. The dissolved ferrioxalate complex ion (Fe(C2O4)33-) is selectively precipitated through subsequent photolysis at room temperature. Depending on the initial concentration, the decomposition ratio can exceed 95 % within 1-4 h. Molecular mechanism analysis reveals that the decomposition of the Fe(C2O4)33- complex ion into water-insoluble FeC2O4·2H2O results in the precipitation of iron and the separation of metal elements. Lithium can be recovered as dihydrogen phosphates through filtration and water evaporation. No additional precipitant is needed and no other side products are generated during the process. Oxalic acid leaching followed by photolysis offers an environmentally friendly and efficient method for metal recovery from spent LFP cathodes. The photochemical process is a promising approach for reducing secondary waste generation in battery recycling.

Evaluation of the deteriorating effects of microbial primary metabolites on silk fibres.

The silk biodegradation process remains unclear and requires elucidation with advanced analytical tools. To address this challenge, the role of microbial primary metabolites in the deterioration of ancient silk was investigated using metabolomics and proteomics techniques in this work. The oxalic and palmitic acids were separately identified as the most abundant organic and fatty acid metabolites for silk-fabric deterioration via metabolomics. Proteomics showed that oxalic acid accelerated the degradation of silk proteins, revealing changes at the molecular level in silk. A high concentration of oxalic acid promoted the dissolution of peptides by activating the cleavage activity of various amino acids on the molecular chain of silk protein. Palmitic acid formed sedimentary particulate matter with peptides solubilised from silk proteins, indicating the possibility that traces of ancient-silk proteins remained in the fatty acids. The work presented new techniques and concepts for studying the degradation of historical fabrics and contributed to the proposal of effective measures to prevent microbial attack on silk.

Synergetic conditioning via oxalic acid enhanced Fe2+/CaO2 and skeleton construct to achieve deep dewatering of sewage sludge.

Extracellular polymeric substance (EPS) with highly hydrophilic groups and sludge with high compressibility are determined sludge dewaterability. Herein, Fe2+ catalyzed calcium peroxide (CaO2) assisted by oxalic acid (OA) Fenton-like process combined with coal slime was applied to improve sludge dewaterability. Results demonstrated that the sludge treated by 0.45/1/1.1-OA/Fe2+/CaO2 mM/g DS, the water content (WC), specific resistance to filtration and capillary suction time dropped to 53.01%, 24.3 s and 1.2 × 1012 m/kg, respectively. Under coal slime ratio as 0.6, WC and compressibility were further reduced to 42.72% and 0.66, respectively. The hydroxyl radicals generated by OA/Fe2+/CaO2 under near-neutral pH layer by layer collapsed EPS, resulting in the degradation and migration of inner releasing components and the exposure of inner sludge flocs skeleton. The hydrophilic tryptophan-like protein of TB-EPS were degraded into aromatic protein of S-EPS and exposed inner hydrophobic sites. The protein secondary structures were transformed by destroying hydrophilic functional groups, which were attributed to the reducing α-helix ratio and reconstructing ß-sheet. Moreover, coal slime as the skeleton builder lowered compressibility and formed more macropores to increase the filterability of pre-oxidized sludge for the higher intensity of rigid substances. This study deepened the understanding of OA enhanced Fenton-like system effects on sludge dewaterability and proposed a cost-effective and synergistic waste treatment strategy in sludge dewatering.

The hemostatic performance and mechanism of palygorskite with structural regulate by oxalic acid gradient leaching.

Palygorskite (Pal) is a naturally available one-dimensional clay mineral, featuring rod-shaped morphology, nanoporous structure, permanent negative charges as well as abundant surface hydroxyl groups, exhibiting promising potential as a natural hemostatic material. In this study, the hemostatic performance and mechanisms of Pal were systematically investigated based on the structural regulate induced by oxalic acid (OA) gradient leaching from perspectives of structure, surface attributes and ion release.In vitroandin vivohemostasis evaluation showed that Pal with OA leaching for 1 h exhibited a superior blood procoagulant effect compared with the raw Pal as well as the others leached for prolonging time. This phenomenon might be ascribed to the synergistic effect of the intact nanorod-like morphology, the increase in the surface negative charge, the release of metal ions (Fe3+and Mg2+), and the improved blood affinity, which promoted the intrinsic coagulation pathway, the fibrinogenesis and the adhesion of blood cells, thereby accelerating the formation of robust blood clots. This work is expected to provide experimental and theoretical basis for the construction of hemostatic biomaterials based on clay minerals.

Fly ash treatment via conventional and microwave-assisted organic acid leaching: kinetics and life cycle assessment.

Heedless disposal of oil-based fly ash contributes to the contamination of the air, water, and soil. Acid leaching of industrial solid wastes is recognized as a versatile, cost-effective, and environmentally friendly solid waste treatment approach. The present study investigated the viability of conventional leaching (CL) and microwave-assisted leaching (MAL) of predominant heavy metals from Mazut-burnt fly ash. For this purpose, the practicality of four organic acids with various specifications (ascorbic, gluconic, citric, and oxalic acids) on the dissolution efficiency of fly ash components was examined. Utilization of oxalic acid led to achieving full V recovery, complete Fe removal, and Ni enrichment in the residue in both CL and MAL setups. The Ni content of the sample was enriched from 6% in the calcinated sample to 23.7% in the oxalic acid leaching residue. Using citric acid resulted in the co-extraction of V, Ni, and Fe with nearly 70% V, 50% Ni, and 89% Fe dissolved in CL. The dissolution efficiencies were slightly lower in MAL. Oxalic acid was selected as the most promising organic acid reagent for fly ash treatment, so its CL kinetics was studied and defined by the shrinking particle model. The model showed that the controlling steps in the leaching of V differ over time, changing from a chemical reaction before 60 min to fluid film diffusion or mixing afterward. The kinetic study proved MAL as an effective technique in overcoming the leaching kinetic barriers. A life cycle assessment study was conducted to determine the environmental impacts of the proposed process. Accordingly, the MAL using oxalic acid was the most environmentally friendly process among the studied ones, and the utilization of microwaves leads to the reduction of the leaching processes' environmental impacts by decreasing the processing time.

Study on green closed-loop regeneration of waste lithium iron phosphate based on oxalic acid system.

The recovery of valuable metals from used lithium batteries is essential from an environmental and resource management standpoint. However, the most widely used acid leaching method causes significant ecological harm. Here, we proposed a method of recovering Li and Fe selectively from used lithium iron phosphate batteries by using low-concentration organic acid and completing the closed-loop regeneration. Low-concentration oxalic acid is used to carry out PO43-, which is significantly less soluble in aqueous solution than Li, two-stage selective leaching Li, where the leaching rate of Li reaches 99 %, and the leaching rate of Fe is only 2.4 %. The leach solution is then decontaminated. The solubility of Li3PO4 in aqueous solution is much smaller than that of Li2C2O4, which was required to recover Li to change the pH and Li can be recovered as Li3PO4; Fe can be retrieved as FeC2O4·2H2O, and re-prepared into lithium iron phosphate.

Rhizosphere environmental factors regulated the cadmium adsorption by vermicompost: Influence of pH and low-molecular-weight organic acids.

Vermicompost is a promising amendment for immobilization of cadmium (Cd) in soils; however, its effectiveness can be influenced by rhizosphere environment conditions, such as pH and the presence of low-molecular-weight organic acids (LMWOAs). In this study, a batch experiment was conducted to examine the characteristics of Cd adsorption by vermicompost at different pH (pH = 3, 5, and 7) and after the addition of different LMWOAs (oxalic acid; citric acid; malic acid). Furthermore, a series of morphology and structural analyses were conducted to elucidate the mechanisms of observed effects. The results showed that the adsorption capacity of vermicompost for Cd increased as pH increased, and chemisorption dominated the adsorption process. Changes in pH altered adsorption performance by affecting the -OH groups of alcohol/phenol and the -CH2 groups of aliphatics. Further, the addition of oxalic acid promoted Cd adsorption, and the effect was concentration dependent. Modifying the verimicompost surface with more adsorption sites might be the main reason. Conversely, citric acid and malic acid showed the ability to inhibit Cd adsorption by vermicompost. Citric acid caused a blocking effect by covering flocculent substances on the vermicompost surface while reducing surface adsorption sites by dissolving mineral components such as iron oxides. However, the action of malic acid did not appear to be related to changes in morphology or the structure of vermicompost. Overall, the results of this study partially explain the limited effectiveness of Cd immobilization within the rhizosphere by vermicompost, and provide theoretical support for regulating rhizosphere environments to improve the effectiveness of vermicompost immobilization of Cd.

Regulatory-systemic approach in Aspergillus niger for bioleaching improvement by controlling precipitation.

In the context of e-waste recycling by fungal bioleaching, nickel and cobalt precipitate as toxic metals by oxalic acid, whereas organic acids, such as citric, act as a high-performance chelating agent in dissolving these metals. Oxalic acid elimination requires an excess and uneconomical carbon source concentration in culture media. To resolve this issue, a novel and straightforward systems metabolic engineering method was devised to switch metabolic flux from oxalic acid to citric acid. In this technique, the genome-scale metabolic model of Aspergillus niger was applied to predicting flux variability and key reactions through the calculation of multiple optimal solutions for cellular regulation. Accordingly, BRENDA regulators and a novel molecular docking-oriented approach were defined a regulatory medium for this end. Then, ligands were evaluated in fungal culture to assess their impact on organic acid production for bioleaching of copper and nickel from waste telecommunication printed circuit boards. The protein structure of oxaloacetate hydrolase was modeled based on homology modeling for molecular docking. Metformin, glutathione, and sodium fluoride were found to be effective as inhibitors of oxalic acid production, enabling the production of 8100 ppm citric acid by controlling cellular metabolism. Indirect bioleaching demonstrated that nickel did not precipitate, and the bioleaching efficiency of copper and nickel increased from 40% and 24% to 61% and 100%, respectively. Bioleaching efficiency was evaluated qualitatively by FE-SEM, EDX, mapping, and XRD analysis. KEY POINTS: • A regulatory-systemic procedure for controlling cellular metabolism was introduced • Metformin inhibited oxalic acid, leading to 8100 ppm citric acid production • Bioleaching of copper and nickel in TPCBs improved by 21% and 76.

Mechanism of catalytic ozonation in expanded graphite aqueous suspension for the degradation of organic acids.

In this study, expanded graphite (EG) was prepared by the oxidation and intercalation of the natural flake graphite using perchloric acid and potassium permanganate at different expansion temperatures (300, 400, 500, and 600°C), and were characterized by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). EG prepared at 500°C was found to be highly effective for the mineralization of oxalic acid aqueous solution during ozonation at pH 3, which was ascribed to the formation of hydroxyl radicals from the surface reaction of surface hydroxyl groups on EG with ozone. The performance of expanded graphite in this catalytic system was basically unchanged after three repeated use. The presence of Cl-, SO42-, HPO42-/H2PO4- and NO3- could inhibit the degradation of oxalic acid in catalytic ozonation with EG. Degradations of oxamic acid and pyruvic acid in catalytic ozonation with EG were pH-dependent, which were lower than that of oxalic acid. The degradations of oxalic acid and oxamic acid were identified as mineralization process by the determination of TOC, while pyruvic acid may transform into organic products such as acetic acid by O3/EG. Manganese ion (Mn2+) could promote the degradation of oxalic acid by O3/EG at pH 3 because permanganate was produced by O3/EG in oxalic acid solution and then reacted with oxalic acid readily at acidic pH. Catalytic ozonation by EG exhibited great application potential for the destruction of refractory organic compounds.

Oxalic acid enhances bioremediation of Cr(VI) contaminated soil using Penicillium oxalicum SL2.

Oxalic acid is the most abundant low molecular weight organic acid (LMWOA) in many environments and offers enormous prospects for treating Cr(VI) contamination. In this study, laboratory batch experiments were conducted to estimate the roles of oxalic acid in Cr(VI) removal by Penicillium oxalicum SL2. Oxalic acid changed the initial pH and provided a suitable condition for the growth of strain SL2 when the penicillium was applied to bioremediation of Cr(VI) contamination in alkaline soil. Gompertz model analysis indicated that initial pH affected the lag time of the growth curve of strain SL2. Scanning electron microscopy and scanning transmission X-ray microscopy analysis showed strain SL2 sufficiently contacted with contaminated soil and reduced Cr(VI) to Cr(III) in the hyphae. The results suggested that oxalic acid could enhance the bioremediation efficiency of strain SL2 though improving chromium bioleaching from the contaminated soil and strengthening Cr(VI) removal in the leaching solution. This study provided oxalic acid as a green reagent for stimulating Cr(VI) removal by strain SL2 and would expand knowledge on the roles of LMWOA in Cr(VI) bioremediation.

Facile and rapid determination of oxalic acid by fading spectrophotometry based on Fe(III)-sulfosalicylate as colorimetric chemosensor.

Spectrophotometry is an economic and rapid method for detecting oxalic acid (OA), while the reported methods have some drawbacks, such as narrow linear range, long response time, delicate operation and required expensive reagents. Herein, we found that the as-synthesized Fe(III)-sulfosalicylate (FeSSA) could be used as an efficient colorimetric chemosensor to detect OA, and the established FeSSA-based fading spectrophotometry showed prominent advantages over the existing ones in detecting OA. The as-established method has wider linear range of 0.80-160 mg/L with regression coefficient ≥ 0.999, while the widest linear range is just 2.7-54 mg/L among the reported ones. Moreover, the method has low limit of detection (0.74 mg/L), extremely fast response (several seconds), satisfactory selectivity, high accuracy and precision. Most importantly, its reliability was further verified by employing it to determine OA concentration during the degradation process of organic pollutants. The measured OA concentration at any time interval was perfectly consistent with those determined by the well-recognized high performance liquid chromatography (HPLC). These confirmed that the FeSSA-based fading spectrophotometry is an efficient, simple, fast, accurate and economic method to determine OA in a wide concentration range.

Manipulating Selectivity of Hydroxyl Radical Generation by Single-Atom Catalysts in Catalytic Ozonation: Surface or Solution.

Hydroxyl radical-dominated oxidation in catalytic ozonation is, in particular, important in water treatment scenarios for removing organic contaminants, but the mechanism about ozone-based radical oxidation processes is still unclear. Here, we prepared a series of transitional metal (Co, Mn, Ni) single-atom catalysts (SACs) anchored on graphitic carbon nitride to accelerate ozone decomposition and produce highly reactive ·OH for oxidative destruction of a water pollutant, oxalic acid (OA). We experimentally observed that, depending on the metal type, OA oxidation occurred dominantly either in the bulk phase, which was the case for the Mn catalyst, or via a combination of the bulk phase and surface reaction, which was the case for the Co catalyst. We further performed density functional theory simulations and in situ X-ray absorption spectroscopy to propose that the ozone activation pathway differs depending on the oxygen binding energy of metal, primarily due to differential adsorption of O3 onto metal sites and differential coordination configuration of a key intermediate species, *OO, which is collectively responsible for the observed differences in oxidation mechanisms and kinetics.

Behaviors of Organic Ligands and Phosphate during Biochar-Driven Nitrate Adsorption in the Presence of Low-Molecular-Weight Organic Acids.

A batch experiment was conducted to examine the behavior of nitrate, organic ligands, and phosphate in the co-presence of biochar and three common low-molecular-weight organic acids (LMWOAs). The results show that citrate, oxalate, and malate ions competed with nitrate ion for the available adsorption sites on the biochar surfaces. The removal rate of LMWOA ligands by the biochar via adsorption grew with increasing solution pH. The adsorbed divalent organic ligands created negatively charged sites to allow binding of cationic metal nitrate complexes. A higher degree of biochar surface protonation does not necessarily enhance nitrate adsorption. More acidic conditions formed under a higher dose of LMWOAs tended to make organic ligands predominantly in monovalent forms and failed to create negatively charged sites to bind cationic metal nitrate complexes. This could adversely affect nitrate removal efficiency in the investigated systems. LMWOAs caused significant release of phosphate from the biochar. The phosphate in the malic acid treatment tended to decrease over time, while the opposite was observed in the citric- and oxalic-acid treatments. This was caused by re-immobilization of phosphate in the former due to the marked increase in solution pH over time.

High-efficiency stabilization of lead in contaminated soil by thermal-organic acid-activated phosphate rock.

Phosphate rock powder (PR) has been shown to possess the potential to stabilize lead (Pb) in soil. Most of the phosphorus (P) minerals in the world are low-grade ores, making it difficult to achieve the expected stabilization effect on heavy metals. This study compared the changes in the phase composition and structure of PR and three kinds of activated phosphate rock powder (APR) (organic acid-activated PR, thermal-activated PR, and thermal-organic acid-activated PR). The stabilization effectiveness of APR on Pb-contaminated soil was evaluated by toxicity leaching procedure; the Pb products adsorbed on APR and stabilization mechanism of APR on Pb were analyzed. The results demonstrated that APR showed decreased crystallinity and 3.4-fold increase in specific surface area, and a 53.07% and 49.32% increase in soluble P content in oxalic acid-activated PR and citric acid-activated PR, respectively, when compared with those of PR. These changes improved the stabilization effect of APR on Pb-contaminated soil, in which oxalic acid-600 °C-activated PR showed the best effect, presenting 94.0-99.8% reduction in Pb leaching concentration following addition of 2-10% modifier. Product characterization after Pb adsorption on APR showed that Pb was adsorbed onto APR by forming fluoropyromophite precipitation with APR.

Oxalic acid activated bone meal for immobilization of Pb and Cd contaminated soils.

Bone meal (BM) is a cost-effective and low-carbon material to remediate heavy metal contaminated soils. Moreover, its immobilization efficiency for heavy metals still requires improvement. This study aimed to assess the activation effect of oxalic acid on the BM to develop an oxalic acid-activated bone meal (ABM) for improving immobilization efficiency. Several series of tests, including the available phosphorus content test, toxicity characteristic leaching procedure (TCLP), modified European Community Bureau of Reference (BCR) sequential extraction procedure, and X-ray diffraction (XRD) analysis, are used to investigate the effect of activation on the immobilization ability and chemical speciation of lead (Pb) and cadmium (Cd) in soils and the different mechanisms of Pb/Cd immobilization using the ABM and BM. The results indicate that the ABM possesses a higher solubility than the BM. The activation of BM achieves optimal effect when using 1 mol/L oxalic acid solution with a liquid-solid ratio of 2:1. The TCLP and BCR test results show that the ABM significantly outperforms the BM in terms of Pb immobilization. The leaching concentration of Pb from ABM immobilized soils can meet regulatory limits in China and the USA, and it is also 30 to 75% lower than that from BM immobilized soils. Regarding Cd immobilization, ABM outperforms BM after 90 days of curing. The XRD analysis shows that heavy metal phosphates are the primary products of Pb and Cd immobilized by ABM, whereas heavy metal carbonates are the main products after the immobilization by BM.

Novel, recyclable Brønsted acidic deep eutectic solvent for mild fractionation of hemicelluloses.

Acidic deep eutectic solvents (DESs) are promising media for lignin valorization and cellulose conversion due to their good ability in efficient deconstruction of plant cell wall. However, hemicellulose extraction from lignocellulose using acidic DESs remains a challenge. Herein, novel and green Brønsted acidic DESs (BDESs) were synthesized from natural organic acids and common polyols and successively adopted to deconstruct corncob for mild fractionation of hemicelluloses. Oxalic acid (OA)-based BDESs were preferred for corncob processing due to the high solubility of xylan. The results revealed that the suitable acidity of DESs and mild temperature effectively avoided the over-degradation of hemicelluloses. The chemical composition and structural features of the recovered hemicelluloses were investigated systematically. Moreover, after ethylene glycol (EG)-OA BDES was recycled and reused three times, the extraction still resulted in a satisfactory hemicellulose yield. The novel and eco-friendly processing offers a practical and sustainable route for hemicellulose extraction in acidic condition.

Copper oxalate formation by lichens and fungi.

The present work focuses on the revealing the patterns of copper oxalates formation under the influence of lichens and fungi by combination of the results of field studies and model experiments. These findings create the scientific basis for the potential microbial technology applications (ore enrichment, monuments conservation, environment bioremediation, etc.). Copper oxalate moolooite Cu(C2O4)·H2O was discovered in saxicolous lichen Lecidea inops on the weathered chalcopyrite ore of Voronov Bor deposit (Central Karelia, Russia). Bioinspired syntheses of moolooite and wheatleyite Na2Cu(C2O4)2 2H2O with the participation of the microscopic fungi Aspergillus niger (active producer of oxalic acid) were carried out on weathered Cu-ore from the Voronov Bor deposit. It was shown that morphology of moolooite crystals is controlled both by the underlying rock and by the species composition of microorganisms. Iron ions (sourced from the underlying rock) in the crystallization medium inhibits the moolooite formation. The observed intensive dissolution of moolooite crystals are well explained by washing effect of the intratalline solutions which depends on repeatedly dehydration / rehydration cycles in the lichens. Joint interpretation of original and published data shows that moolooite along with other cooper oxalates are biominerals.