Heavy metal compounds are used in a variety of industrial processes, including tanning, chrome plating, anti-corrosion treatments, and wood preservation. Heavy metal ion pollution in water and wastewater is often caused by industrial effluent discharge into open water sources. Toxic heavy metal ions such as As (III), Cr (VI), Cd (II), and Pb (II) are well-known and enter the body through a variety of pathways, including the food chain, respiration, skin absorption, and drinking water. These heavy metal ions produce oxidative stress in cells, resulting in cell organelle destruction. Heavy metals produce toxicity and may cause genetic material mutation or change, histone modification, and epigenetic alteration at various stages. Furthermore, heavy metals are linked to heart failure, renal damage, liver failure, and a variety of skin problems. For heavy metals cleanup, several standard approaches are utilized. Nonetheless, these technologies are costly and result in toxic sludge after treatment. As a result, there is an urgent need for an appropriate, environmentally safe, and efficient heavy metal removal technology. For heavy metal removal, microbial-based approaches are regarded as both environmentally benign and cost-effective. This review focuses on heavy metal pollution in water, its harmful consequences, and heavy metal cleanup by microbiological means.

The rapid progress of urbanization and industrialization has led to the accumulation of large amounts of metal ions in the environment. These metal ions are adsorbed onto the negatively charged surfaces of clay particles, altering the total surface charge, double-layer thickness, and chemical bonds between the particles, which in turn affects the interactions between them. This causes changes in the microstructure, such as particle rearrangement and pore morphology adjustments, ultimately altering the mechanical behavior of the soil and reducing its stability. This study explores the effects of four common metal ions, including monovalent alkali metal ions (Na+, K+) and divalent heavy metal ions (Pb2+, Zn2+), with a focus on how ion valence and concentration impact the soil's microstructure and mechanical properties. Microstructural tests show that metal ion incorporation reduces particle size, increases clay content, and transforms the structure from layered to honeycomb-like. Small pores decrease while large pores dominate, reducing the specific surface area and pore volume, while the average pore size increases. Although cation exchange capacity decreases, cation adsorption density per unit surface area increases. Monovalent ions primarily disperse the soil structure, while divalent ions induce coagulation. Macro-mechanical tests reveal that metal ion contamination reduces porosity under loading, with compressibility rises as the ion concentration increases. Soils contaminated with alkali metal ions shows higher compression coefficients at all loads, while heavy metal ions cause higher compression under lower loads. Shear strength, the internal friction angle, and cohesion in metal-ion-contaminated clay decrease compared to uncontaminated field-state clay, with greater declines at higher ion concentrations. The Micropore Morphology Index and hydro-pore structural parameter effectively characterize both micro- and macrostructural properties, establishing a quantitative relationship between HPSP and the engineering properties of metal-ion-contaminated clay.

Highly-stable heavy metal ions (HMIs) appear long-term damage, while the existing remediation strategies struggle to effectively remove a variety of oppositely charged HMIs without releasing toxic substances. Here we construct an iron-copper primary battery-based nanocomposite, with photo-induced protonation effect, for effectively consolidating broad-spectrum HMIs. In FCPBN, Fe/Cu cell acts as the reaction impetus, and functional graphene oxide modified by carboxyl and UV-induced protonated 2-nitrobenzaldehyde serves as an auxiliary platform. Due to the groups and built-in electric fields under UV stimuli, FCPBN exhibits excellent affinity for ions, with a maximum adsorption rate constant of 974.26 g center dot mg-1 center dot min-1 and facilitated electrons transfer, assisting to reduce 9 HMIs including Cr2O72-, AsO2- , Cd2+ in water from 0.03 to 3.89 ppb. The cost-efficiency, stability and collectability of the FCPBN during remediation, and the beneficial effects on polluted soil and the beings further demonstrate the splendid remediation performance without secondary pollution. This work is expected to remove multi-HMIs thoroughly and sustainably, which tackles an environmental application challenge.

Globally, soil acidification is a serious environmental issue that reduces commercial agricultural production. Rice is subjected to nutritional stress due to acidic soil, which is a major impediment to rice production. Since acid soil threatens rice plants with soil compaction, nutrient loss, and plant stress-induced oxidative cell damage that results in affecting the photosynthetic system, restricting the availability of water, and reducing overall plant growth and productivity. Since contemporary soil acidification management strategies provide mediocre results, the use of Sargassum wightii seaweed-based biostimulants (BS) and soil amendments is sought as an environmentally friendly alternative strategy, and therefore its potential isevaluated in this study. BS was able to mediate soil quality by improving soil pH and structure along with facilitating nitrogen phytoavailability. BS also increased the activity of the antioxidant enzyme system, superoxide dismutase ((48%), peroxidase (76.6%), and ascorbate peroxidase (63.5%), aggregating the monaldehyde-mediating accumulation of osmoprotective proline in roots, that was evident from rapid initiation of root hair growth in treated seedlings. BS was also able to physiologically modulate photosynthetic activities and chlorophyll production (24.31%) in leaves, maintaining the efficiency of plant water use by regulating the stomatal conductance (0.91 mol/m/s) and the transpiration rate (13.2 mM/m/s). The BS compounds were also successful in facilitating nitrogen uptake resulting in improved plant growth (59%), tiller-panicle number, and yield (52.57%), demonstrating a resourceful nitrogen use efficiency (71.96%) previously affected by stress induced by acid soil. Therefore, the study affirms the competent potential of S. wightii-based soil amendment to be applied not only to improve soil quality, but also to increase plant production and yield.

Agrichemical losses are a severe threat to the ecological environment. Additionally, some agrichemical compounds contain abundant salt, which increases the instability of formulations, leading to a lower agrichemical utilization and soil hardening. Fortunately, the biological amphiphilic emulsifier sodium deoxycholate alleviates these problems by forming stable Janus core-shell emulsions through salinity-driven interfacial self-assembly. According to the interfacial behavior, dilational rheology, and molecular dynamics simulations, Janus-emulsion molecules are more closely arranged than traditional-emulsion molecules and generate an oil-water interfacial film that transforms into a gel film. In addition, at the same spray volume, the deposition area of the Janus emulsion increased by 37.70% compared with that of the traditional emulsion. Owing to the topology effect and deformation, the Janus emulsion adheres to rice micropapillae, achieving better flush resistance. Meanwhile, based on response of the Janus emulsion to stimulation by carbon dioxide (CO2), the emulsion lost to the soil can form a rigid shell for inhibiting the release of pesticides and metal ions from harming the soil. The pyraclostrobin release rate decreased by 50.89% at 4 h after the Janus emulsion was exposed to CO2. The Chao1 index of the Janus emulsion was increased by 12.49% as compared to coconut oil delivery in soil microbial community. The Janus emulsion ingested by harmful organisms can be effectively absorbed in the intestine to achieve better control effects. This study provides a simple and effective strategy, which turns waste into treasure, by combining metal ions in agrichemicals with natural amphiphilic molecules to prepare stable emulsions for enhancing agrichemical rainfastness and weakening environmental risk.

An imbalance between available resource reserves generated by human activities and disposal measures causes a series of harmful problems related to water, soil and human health, such as those from hazardous metal ions (HMs) and their carrier materials (LMs). As excellent intermediates with adjustable spatial structures and many active sites, geopolymers can be directly used as adsorbents to remove HMs from wastewater or produced by LMs via in situ stabilization/solidification methods. This paper first reviews the common methods used to optimize the pore structures of geopolymers and then reports the common methods for optimizing LM-based geopolymers. For geopolymers-based adsorbents, the pore structure is vital in the adsorption of the target ions, and the application of functional auxiliary materials among adsorbents has been summarized. The feasibility of using geopolymers for in situ stabilization/solidification of HMs is highlighted, but instability and low mechanical strength remain significant factors hindering their development. Finally, the mechanism for bonding between HMs and geopolymers is summarized, and future developments, challenges, and possible solutions are briefly described.

Converting agricultural residues into environmentally friendly adsorbents to address the problem of low removal efficiency of low-concentration heavy metal ions is an effective strategy for high-value utilization of agricultural residues. Herein, a simple general strategy is proposed for constructing amphoteric agricultural residues-based porous adsorbents by forming anisotropic cross-linked structures at the heterogeneous interface of agricultural residue, coconut shell carbon, and polyethyleneimine. This green preparation strategy can be widely adapted to agricultural residues with hydroxyl structures, such as bagasse fiber, corn cob, and peanut shell, to prepare highperformance adsorbents with high densities of amphoteric adsorption sites (The density of amino and carboxyl groups was 3.44 mmol & sdot;g- 1 and 3.64 mmol & sdot;g- 1) while maintaining a developed microporous structure (BET specific surface area of 760.68 m2 & sdot;g- 1), the reactant conversion rate was higher than 99 %. Interestingly, the synergistic effect of abundant amphoteric functional groups and developed microporous structures enabled the adsorbents to completely remove Cr(VI), Cu(II), Pb(II), and Cd(II) from water within 10 min, which exhibited a promising synchronous removal efficiency for multiple heavy metal ions. It provides a reference for the remediation of heavy metals contaminated groundwater and soil by agricultural residues-based adsorbent.

Biomass-based alternatives to soil improvement by cement in geotechnical applications are increasingly considered owing to their renewability and low carbon footprint. We have elaborated a method of soil improvement by which soil is treated with self-organizing biomass-derived polyions, carboxymethyl cellulose (CMC), and chitosan (CS) and is consequently compacted by rammer. CMC and CS interact electrostatically and self-assemble into interpolyelectrolyte complexes (IPEC) having the morphology of thin films imparting the superior mechanical properties to the soil composite. Curing of soil with CMC and CS at m(CMC+CS)/m(soil) ratios below 1% and compaction improved the unconfined compressive strength (qu) of soil up to 500 kPa in a wet state (ca. 17% moisture content) and 2.5 MPa in a dry state (ca. 0% moisture content). Due to the superior complexing properties of CMC and CS towards transition metal ions, soil treatment with IPEC notably suppressed the leaching of Cu2+, Pd2+, and Cd2+ metal ions from the soil. Despite the intrinsic biodegradability of CMC and CS, their IPEC complexes and soil-IPEC composites showed good resistance toward biodegradation by the cellulase enzyme. Excellent soil reinforcement, suppressed biodegradability, and chemical functionality of biomass-derived IPECs hold promise in utilizing renewable polymers in geotechnical practices of ground improvement addressing the needs of the sustainable use of resources.