Microbially induced calcite precipitation (MICP) through a ureolytic pathway is a process that promotes calcite precipitation as a result of the urease enzymatic activity of several microorganisms. It has been studied for different technological applications, such as soil bio-consolidation, bio-cementation, CO₂ sequestration, among others. Recently, this process has been proposed as a possible process for removing heavy metals from contaminated soils. However, no research has been reported dealing with the MICP process for heavy metal removal from wastewater/waters. This (re)view proposes to consider to such possibility. The main characteristics of MICP are presented and discussed. The precipitation of heavy metals contained in wastewaters/waters via MICP is exanimated based on process characteristics. Moreover, challenges for its successful implementation are discussed, such as the heavy metal tolerance of inoculum, ammonium release as product of urea hydrolysis, and so on. A semi-continuous operation in two steps (cell growth and bio-precipitation) is proposed. Finally, the wastewater from some typical industries releasing heavy metals are examined, discussing the technical barriers and feasibility.

This research focused on the evaluation of the potential use of a soil-isolated bacteria, identified as Staphylococcus equorum, for microbial-induced calcite precipitation (MICP) and copper removal. Isolated bacteria were characterized considering growth rate, urease activity, calcium carbonate precipitation, copper tolerance as minimum inhibitory concentration (MIC) and copper precipitation. Results were compared with Sporosarcina pasteurii, which is considered a model bacteria strain for MICP processes. The results indicated that the S. equorum strain had lower urease activity, calcium removal capacity and copper tolerance than the S. pasteurii strain. However, the culture conditions tested in this study did not consider the halophilic feature of the S. equorum, which could make it a promising bacterial strain to be applied in process water from mining operations when seawater is used as process water. On the other hand, copper removal was insufficient when applying any of the bacteria strains evaluated, most likely due to the formation of a copper–ammonia complex. Thus, the implementation of S. equorum for copper removal needs to be further studied, considering the optimization of culture conditions, which may promote better performance when considering calcium, copper or other metals precipitation.

A series of tetrabutyl ammonium (TBA) salts of V-included Keggin-type polyoxoanions with W (TBA₄PW₁₁V₁O₄₀ and TBA₅PW₁₀V₂O₄₀) and Mo (TBA₄PMo₁₁V₁O₄₀ and TBA₅PMo₁₀V₂O₄₀) as addenda atoms were prepared using a hydrothermal method. These synthesized materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV-Vis diffuse reflectance (DRS UV-Vis), thermogravimetric analysis (TGA), CHN elemental analysis (EA), inductively coupled plasma spectrometry (ICP-MS), and N₂ physisorption techniques to assess their physicochemical/textural properties and correlate them with their catalytic performances. According to FT-IR and DRS UV-Vis, (PV_XW(Mo)_12−XO₄₀)^(3+X)− anions are the main species present in the TBA salts. Additionally, CHN-EA and ICP-MS revealed that the desired stoichiometry was obtained. Their catalytic activities in the liquid-phase aerobic oxidation of benzyl alcohol to benzaldehyde were studied at 5 bar of O₂ at 170 °C. Independently of the addenda atom nature, the catalytic activity increased with the number of V in the Keggin anion structure. For both series of catalysts, TBA salts of polyoxometalates with the highest V-substitution degree (TBA₅PMo₁₀V₂O₄₀ and TBA₅PW₁₀V₂O₄₀) showed higher activity. The maximum benzyl alcohol conversions obtained were 93% and 97% using (TBA)₅PMo₁₀V₂O₄₀ and (TBA)₅PW₁₀V₂O₄₀ as catalysts, respectively. In all the cases, the selectivity toward benzaldehyde was higher than 99%.

This study evaluated the stability and reusability of amino-functionalized nanocellulose aerogels as CO₂-adsorbent materials. The modified aerogels, synthesized via a controlled silylation using N-[3-(trimethoxysilyl) propyl] ethylenediamine (DAMO), demonstrated excellent thermal stability up to 250 °C (TGA) and efficient CO₂ adsorption through chemisorption, which was the main adsorption mechanism. The performance of the aerogels was assessed using both adsorption isotherms and the decay pressure technique, revealing that CO₂ adsorption capacity increased with higher amino group loading (4.62, 9.24, and 13.87 mmol of DAMO). At 298 K and 4 bar, CO₂ adsorption capacity increased proportionally with the amino group concentration, reaching values of 3.17, 5.98, and 7.86 mmol of CO₂ g⁻¹ polymer, respectively. Furthermore, over 20 adsorption/desorption cycles, the aerogels maintained 95% CO₂ desorption at ambient temperature, indicating their potential for industrial use. These findings highlight the aerogels suitability as stable, reusable materials for large scale CO₂ capture and storage technologies.

The catalytic oxidation of phenethoxybenzene as a lignin model compound with a β-O-4 bond was conducted using the Keggin-type polyoxometalate nanocatalyst (TBA)₅[PMo₁₀V₂O₄₀]. The optimization of the process’s operational conditions was carried out using response surface methodology. The statistically significant variables in the process were determined using a fractional factorial design. Based on this selection, a central circumscribed composite experimental design was used to maximize the phenethoxybenzene conversion, varying temperature, reaction time, and catalyst load. The optimal conditions that maximized the phenethoxybenzene conversion were 137 °C, 3.5 h, and 200 mg of catalyst. In addition, under the optimized conditions, the Kraft lignin catalytic depolymerization was carried out to validate the effectiveness of the process. The depolymerization degree was assessed by gel permeation chromatography from which a significant decrease in the molar mass distribution Mw from 7.34 kDa to 1.97 kDa and a reduction in the polydispersity index PDI from 6 to 3 were observed. Furthermore, the successful cleavage of the β-O-4 bond in the Kraft lignin was verified by gas chromatography–mass spectrometry analysis of the reaction products. These results offer a sustainable alternative to efficiently converting lignin into valuable products.

This study evaluates the antimicrobial properties of nanocomposite materials based on polyvinyl alcohol (PVA) reinforced with cellulose nanofibrils (CNFs) and/or supplement-ed with biobased additives derived from blueberry pruning wastes, with the objective of developing biodegradable food packaging systems with antimicrobial properties. The nanocomposites were prepared using a solvent-casting processing approach, and their thermal, physicochemical, and antimicrobial properties were assessed. All the nanocomposites exhibited thermal stability up to 200 °C, confirming their suitabil-ity for conventional food packaging processing conditions. Antimicrobial activity tests re-vealed inhibitory effects against both Gram-positive and Gram-negative bacteria. Bleached PVA/CNFs films showed complete growth inhibition (100%) against E. coli and S. aureus. In contrast, unbleached PVA/CNFs and PVA/CNFsB supplemented with blueber-ry-derived additives exhibited selective inhibition against E. coli, highlighting the influ-ence of nanofibril composition and additive incorporation on antimicrobial performance. Zeta potential measurements revealed values of –35.3 mV for the CNFs, confirming their negatively charged surface, which may contribute to interactions with bacterial mem-branes. Additionally, scanning electron microscopy (SEM) showed that the incorporation of CNFs generates nanostructured surfaces with exposed fibrillar domains, where bacteri-al cells become adhered and immobilized. These topographical features suggest that the antimicrobial behavior of the nanocomposites is associated with direct bacteria–surface interactions, supporting a contact-active antimicrobial behavior associated with the CNFs.