Enzyme-induced carbonate precipitation (EICP) has been studied in remediation of heavy metal contaminated water or soil in recent years. This paper aims to investigate the immobilization mechanism of Zn2+, Ni2+, and Cr(VI) in contaminated sand, as well as strength enhancement of sand specimens by using EICP method with crude sword bean urease extracts. A series of liquid batch tests and artificially contaminated sand remediation experiments were conducted to explore the heavy metal immobilization efficacy and mechanisms. Results showed that the urea hydrolysis completion efficiency decreased as the Ca2+ concentration increased and the heavy metal immobilization percentage increased with the concentration of Ca2+ and treatment cycles in contaminated sand. After four treatment cycles with 0.5 mol/L Ca2+ added, the immobilization percentage of Zn2+, Ni2+ and Cr(VI) were 99.99 %, 86.38 %, and 75.18 %, respectively. The microscale analysis results presented that carbonate precipitates and metallic oxide such as CaCO3, ZnCO3, NiCO3, Zn(OH)2, and CrO(OH) were generated in liquid batch tests and sand remediation experiments. The SEM-EDS and FTIR results also showed that organic molecules and CaCO3 may adsorb or complex heavy metal ions. Thus, the immobilization mechanism of EICP method with crude sword bean urease can be considered as biomineralization, as well as adsorption and complexation by organic matter and calcium carbonate. The unconfined compressive strength of EICP-treated contaminated sand specimens demonstrated a positive correlation with the increased generation of carbonate precipitates, being up to 306 kPa after four treatment cycles with shear failure mode. Crude sword bean urease with 0.5 mol/L Ca2+ added is recommended to immobilize multiple heavy metal ions and enhance soil strength.

Calcification and biomass production by planktonic marine organisms influences the global carbon cycle and fuels marine ecosystems. The major calcifying plankton group coccolithophores are highly diverse, comprising ca. 250-300 extant species. However, coccolithophore size (a key functional trait) and degree of calcification are poorly quantified, as most of our understanding of this group comes from a small number of species. We generated a novel reference dataset of coccolithophore morphological traits, including cell-specific data for coccosphere and cell size, coccolith size, number of coccoliths per cell, and cellular calcite content. This dataset includes observations from 1074 individual cells and represents 61 species from 25 genera spanning equatorial to temperate coccolithophore populations that were sampled during the Atlantic Meridional Transect (AMT) 14 cruise in 2004. This unique dataset can be used to explore relationships between morphological traits (cell size and cell calcite) and environmental conditions, investigate species-specific and community contributions to pelagic carbonate production, export and plankton biomass, and inform and validate coccolithophore representation in marine ecosystem and biogeochemical models.

Chromium contamination from abandoned industrial sites and inadequately managed waste disposal areas poses substantial environmental threat. Microbially induced carbonate precipitation (MICP) has shown promising, eco-friendly solution to remediate Cr(VI) and divalent heavy metals. In this study, MICP was carried out for chromium immobilization by an ureolytic bacterium Arthrobacter creatinolyticus which is capable of reducing Cr(VI) to less toxic Cr(III) via extracellular polymeric substances (EPS) production. The efficacy of EPS driven reduction was confirmed by cellular fraction analysis. MICP carried out in aqueous solution with 100 ppm of Cr(VI) co-precipitated 82.21% of chromium with CaCO3 and the co-precipitation is positively correlated with reduction of Cr(VI). The organism was utilized to remediate chromium spiked sand and found that MICP treatment decreased the exchangeable fraction of chromium to 0.54 ± 0.11% and increased the carbonate bound fraction to 26.1 ± 1.15% compared to control. XRD and SEM analysis revealed that Cr(III) produced during reduction, influenced the polymorph selection of vaterite during precipitation. Evaluation of MICP to remediate Cr polluted soil sample collected from Ranipet, Tamil Nadu also showed effective immobilization of chromium. Thus, A. creatinolyticus proves to be viable option for encapsulating chromium contaminated soil via MICP process, and effectively mitigating the infiltration of Cr(VI) into groundwater and adjacent water bodies.

The primary purpose of the study, as part of the planned conservation work, was to uncover all aspects of autochthonous biofilm pertaining to the formation of numerous deterioration symptoms occurring on the limestone Rožanec Mithraeum monument in Slovenia. Using state-of-the-art sequencing technologies combining mycobiome data with observations made via numerous light and spectroscopic (FTIR and Raman) microscopy analyses pointed out to epilithic lichen Gyalecta jenensis and its photobiont, carotenoid-rich Trentepohlia aurea, as the origin of salmon-hued pigmented alterations of limestone surface. Furthermore, the development of the main deterioration symptom on the monument, i.e., biopitting, was instigated by the formation of typical endolithic thalli and ascomata of representative Verrucariaceae family (Verrucaria sp.) in conjunction with the oxalic acid-mediated dissolution of limestone. The domination of lichenized fungi, as the main deterioration agents, both on the relief and surrounding limestone, was additionally supported by the high relative abundance of lichenized and symbiotroph groups in FUNGuild analysis. Obtained results not only upgraded knowledge of this frequently occurring but often overlooked group of extremophilic stone heritage deteriogens but also provided a necessary groundwork for the development of efficient biocontrol formulation applicable in situ for the preservation of similarly affected limestone monuments.

The glycolysis process of flexible polyurethane foams containing styrene-acrylonitrile and calcium carbonate as fillers was explored in detail. The use of DABCO as a catalyst allowed us to reduce the catalyst concentration and the polyurethane-to-glycol mass ratio to 0.1% and 1:1, respectively. The glycolysis process allowed us to obtain a high-purity polyol (99%), which can totally replace raw polyols in the synthesis of new flexible polyurethane foams, maintaining the standard mechanical properties of the original one and modifying the ratio of isocyanates employed to correct the closed cell structure caused by the impurities present in the recovered polyol. This isocyanate mixture was also optimized, resulting in a ratio of 30 and 70% of the isocyanates TDI80 and TDI65, respectively. Additionally, the fillers incorporated in the glycolyzed foams were recovered. Both recovered fillers, styrene-acrylonitrile and calcium carbonate, were fully characterized, showing a quality very similar to that of commercial compounds. Finally, the replacement of commercial fillers by the recovered ones in the synthesis of new polyurethane foams was studied, demonstrating the feasibility of using them in the synthesis of new foams without significantly altering their properties.

Carbonate minerals are ubiquitous in nature, and their dissolution impacts many environmentally relevant processes including preferential flow during geological carbon sequestration, pH buffering with climate-change induced ocean acidification, and organic carbon bioavailability in melting permafrost. In this study, we advance the atomic level understanding of calcite dissolution mechanisms to improve our ability to predict this complex process. We performed high pressure and temperature (1300 psi and 50 °C) batch experiments to measure transient dissolution of freshly cleaved calcite under H2O, H+, and H2CO3-dominated conditions, without and with an inhibitory anionic surfactant present. Before and after dissolution experiments, we measured dissolution etch-pit geometries using laser profilometry, and we used density functional theory to investigate relative adsorption energies of competing species that affect dissolution. Our results support the hypothesis that calcite dissolution is controlled by the ability of H2O to preferentially adsorb to surface Ca atoms over competing species, even when dissolution is dominated by H+ or H2CO3. More importantly, we identify for the first time that adsorbed H+ enhances the role of water by weakening surface Ca-O bonds. We also identify that H2CO3 undergoes dissociative adsorption resulting in adsorbed HCO3- and H+. Adsorbed HCO3- that competes with H2O for Ca acute edge sites inhibits dissolution, while adsorbed H+ at the neighboring surface of CO3 enhances dissolution. The net effect of the dissociative adsorption of H2CO3 is enhanced dissolution. These results will impact future efforts to more accurately model the impact of solutes in complex water matrices on carbonate mineral dissolution.

Ecological restoration of bauxite residue has received extensive attention, and organic matter plays a crucial role in the soil formation process of bauxite residue. However, the interaction between organic matter and alkaline minerals in bauxite residue is not well understood. In this work, molecular spectroscopic techniques combined with isothermal titration calorimetry (ITC) were employed to investigate the interactions between humic acid (HA) and four representative alkaline minerals in bauxite residue (calcite, garnet, sodalite, and cancrinite). The results show that the adsorption processes of HA onto calcite and garnet were primarily governed by monolayer surface adsorption and controlled by surface reactions, which were different for sodalite and cancrinite. Both garnet and cancrinite had strong binding affinities with fluorescent HA, while cancrinite only bound with a small fraction of HA. In contrast, the bindings of calcite and sodalite with fluorescent HA were weak. The ITC results indicate distinct thermodynamic properties of different alkaline minerals in the interaction with HA. The molar enthalpy of calcite was - 45.88 kJ/mol, which was much higher than those of garnet, sodalite, and cancrinite, suggesting that calcite exhibited a relatively uniform interaction mechanism with HA dominated by enthalpy change, while the others showed heterogeneous entropy-driven mechanisms. The findings contribute to a better understanding on the microscale connections between organic matter and alkaline minerals in bauxite residue.

Hip fractures are a major health issue considerably impacting patients\' quality of life and well-being. This is particularly evident in elderly subjects, in which the decline in bone and muscle mass coexists and predisposes individuals to fall and fracture. Among interventions to be implemented in hip fractured patients, the assessment and management of nutritional status is pivotal, particularly in subjects older than 65. Nutrition plays a central role in both primary and secondary preventions of fracture. An adequate protein intake improves muscle mass and strength and the intestinal absorption of calcium. Other nutrients with recognized beneficial effects on bone health are calcium, vitamins D, K, and C, potassium, magnesium, folate, and carotenoids. With reference to calcium, results from longitudinal studies showed that the consumption of dairy foods has a protective role against fractures. Moreover, the most recent systematic reviews and meta-analyses and one umbrella review demonstrated that the combination of calcium and vitamin D supplementation significantly reduces hip fracture risk, with presumed higher efficacy in older and institutionalized subjects. Owing to these reasons, the adequate intake of calcium, vitamin D, protein, and other macro and micronutrients has been successfully implemented in the Fracture Liaison Services (FLSs) that represent the most reliable model of management for hip fracture patients. In this narrative review, papers (randomized controlled trials, prospective and intervention studies, and systematic reviews) retrieved by records from three different databases (PubMed, Embase, and Medline) have been analyzed, and the available information on the screening, assessment, and management of nutritional and vitamin D status and calcium intake in patients with hip fractures is presented along with specific prevention and treatment measures.

This study investigates the co-precipitation of calcium and barium ions in hypersaline wastewater under the action of Bacillus licheniformis using microbially induced carbonate precipitation (MICP) technology, as well as the bactericidal properties of the biomineralized product vaterite. The changes in carbonic anhydrase activity, pH, carbonate and bicarbonate concentrations in different biomineralization systems were negatively correlated with variations in metal ion concentrations, while the changes in polysaccharides and protein contents in bacterial extracellular polymers were positively correlated with variations in barium concentrations. In the mixed calcium and barium systems, the harvested minerals were vaterite containing barium. The increasing concentrations of calcium promoted the incorporation and adsorption of barium onto vaterite. The presence of barium significantly increased the contents of O-CO, N-CO, and Ba-O in vaterite. Calcium promoted barium precipitation, but barium inhibited calcium precipitation. After being treated by immobilized bacteria, the concentrations of calcium and barium ions decreased from 400 and 274 to 1.72 and 0 mg/L (GB/T15454-2009 and GB8978-1996). Intracellular minerals were also vaterite containing barium. Extracellular vaterite exhibited bactericidal properties. This research presents a promising technique for simultaneously removing and recycling hazardous heavy metals and calcium in hypersaline wastewater.

While the extensive utilization of disposable plastic straws has resulted in significant environmental issues such as microplastics and soil and ocean pollution, the quest for alternative straws for versatile use remains a formidable challenge. Here, drawing inspiration from naturally water-resistant materials such as bones and sea urchins, we have developed seaweed-based straws with significantly improved water resistance and mechanical strength via in-situ mineralization of CaCO3 on their surfaces. Specifically, the COO- groups on the G (α-L-guluronate) blocks of alginate were employed to establish a robust cross-linked network, while the COO- groups on the M (β-D-mannuronate) blocks attracted free Ca2+ through electrostatic forces, thereby promoting CaCO3 nucleation. This effectively prevents COOH groups from hydrating, reducing swelling, and results in the fabrication of nano- to micron-sized CaCO3 particles that reinforce the structure without compromising the cross-linked network. Compared with the control group, the S5% sample (prepared with 5 % Na2CO3 solution) exhibited a 102 % increase in water contact angle, a 35 % decrease in swelling degree, and a 35.5 % and 37.5 % increase in ultimate flexural and tensile stress, respectively. Furthermore, the potential use of these straws as a waste for heavy metal adsorption was investigated, addressing environmental concerns while demonstrating economic feasibility.