Preparation and characteristics of bentonite-zeolite adsorbent and its application in swine wastewater

Selective recovery of esterase from Trichoderma harzianum through adsorption: Insights on enzymatic catalysis, adsorption isotherms and kinetics

In recent years, numerous attempts have been made to develop a low-cost adsorbent for selectively recovering industrially important products from fermentation broth or complex mixtures. The current study is a novel attempt to selectively adsorb esterase from Trichoderma harzianum using cheap adsorbents like bentonite (BT), activated charcoal (AC), silicon dioxide (SiO2), and titanium dioxide (TiO2). AC had the highest esterase adsorption of 97.58% due to its larger surface area of 594.45 m3/g. SiO2 was found to have the highest selectivity over esterase, with an estimated purification fold of 7.2. Interestingly, the purification fold of 5.5 was found in the BT-extracted fermentation broth. The functional (FT-IR) and morphological analysis (SEM-EDX) were used to characterize the adsorption of esterase. Esterase adsorption on AC, SiO2, and TiO2 was well fitted by Freundlich isotherm, demonstrating multilayer adsorption of esterase. A pseudo-second-order kinetic model was developed for esterase adsorption in various adsorbents. Thermodynamic analysis revealed that adsorption is an endothermic process. AC has the lowest Gibbs free energy of -10.96 kJ/mol, which supports the spontaneous maximum adsorption of both esterase and protein. In the desorption study, the maximum recovery of esterase from TiO2 using sodium chloride was 41.34 %. Unlike other adsorbents, the AC-adsorbed esterase maintained its catalytic activity and stability, implying that it could be used as an immobilization system for commercial applications. According to the kinetic analysis, the overall rate of the reaction was controlled by reaction kinetics rather than external mass transfer resistance, as indicated by the Damkohler number.

Recent advances of application of bentonite-based composites in the environmental remediation

Bentonite-based composites have been widely utilized in the removal of various pollutants due to low cost, environmentally friendly, ease-to-operate, whereas the recent advances concerning the application of bentonite-based composites in environmental remediation were not available. Herein, the modification (i.e., acid/alkaline washing, thermal treatment and hybrids) of bentonite was firstly reviewed; Then the recent advances of adsorption of environmental concomitants (e.g., organic (dyes, microplastics, phenolic and other organics) and inorganic pollutants (heavy metals, radionuclides and other inorganic pollutants)) on various bentonite-based composites were summarized in details. Meanwhile, the effect of environmental factors and interaction mechanism between bentonite-based composites and contaminants were also investigated. Finally, the conclusions and prospective of bentonite-based composites in the environmental remediation were proposed. It is demonstrated that various bentonite-based composites exhibited the high adsorption/degradation capacity towards environmental pollutants under the specific conditions. The interaction mechanism involved the mineralization, physical/chemical adsorption, co-precipitation and complexation. This review highlights the effect of different functionalization of bentonite-based composites on their adsorption capacity and interaction mechanism, which is expected to be helpful to environmental scientists for applying bentonite-based composites into practical environmental remediation.

Copper and zinc interact significantly in their joint toxicity to Chlamydomonas reinhardtii: Insights from physiological and transcriptomic investigations

Copper (Cu) and zinc (Zn) often discharge simultaneously from industrial and agricultural sectors and cause stress to aquatic biota. Although microalgae have been extensively investigated for their responses to Cu or Zn exposure, how they cope with the mixtures of two metals, especially at transcriptomic level, remains largely unknown. In this study, Chlamydomonas reinhardtii was exposed to environmentally relevant concentrations of two metals. It was found that Zn promoted the entry of Cu into the algal cells. With the increase of combined toxicity, extracellular polymeric substances (EPS) and cell wall functional groups immobilized significant amounts of Cu and Zn. Furthermore, C. reinhardtii adjusted resistance strategies internally, including starch consumption and synthesis of chlorophyll and lipids. Upon high level of Cu and Zn coexistence, synergistic effects were observed in lipid peroxidation and catalase (CAT) activity. Under 1.05 mg/L Cu + 0.87 mg/L Zn, 256 differentially expressed genes (DEGs) were mainly involved in oxidative phosphorylation, ribosome, nitrogen metabolism; while 4294 DEGs induced by 4.21 mg/L Cu + 3.48 mg/L Zn were mainly related to photosynthesis, citric acid cycle, etc. Together, this study revealed a more comprehensive understanding of mechanisms of Cu/Zn detoxification in C. reinhardtii, emphasizing critical roles of photosynthetic carbon sequestration and energy metabolism in the metal resistance.

Assessment of health safety of pigs taking natural sorbents with feed

BACKGROUND

The study assessed the effect of smectites (bentonite and zeolite) used as natural sorbents in the diet of pigs on feed digestibility, health parameters, the severity of anatomo-histological changes in organs, and the accumulation of volatile pollutants in organs.

MATERIAL AND METHODS

The study was conducted using fattening pigs (crossbreds from multiple breeds) assigned to three groups - a control (C) and two experimental groups (A and B), with 240 pigs in each group (3 replicates × 80). The animals in group C received a standard complete diet, while groups A and B received diets with 1.5% composed smectite sorbents. The feed and faeces were analysed for content of dry matter, crude ash, crude protein, ether extract, and crude fibre. The content of P was determined using a Helios Alpha UV-VIS spectrophotometer. Whole blood was analysed for haematological parameters and serum for biochemical parameters. Tissue samples were collected for analysis of volatile substances and histological analysis. After slaughter, samples of the lungs, liver, kidneys and jejunum were collected for morphological evaluation, and samples of the perirenal fat, liver, kidneys, lungs and brain for headspace gas chromatography (GC) to determine the levels of volatile toxic substances.

RESULTS

A statistical increase in the digestibility of crude fibre and an increase in that of P were observed in both experimental groups (A and B) in comparison to the control. The whole blood and serum of the pigs from the control group had statistically significantly higher levels of creatinine, urea, and Mg and a higher WBC count compared to both experimental groups (A and B).

CONCLUSIONS

The feed additives were not shown to have a negative effect on the health parameters analysed or on accumulation of pollutants in selected tissues. No significant effect on the digestibility of most nutrients was observed; only an increase in the digestibility of crude fibre and a decrease in P digestibility were noted in the experimental groups.

Modification of naturally abundant resources for remediation of potentially toxic elements: A review

Water and soil contamination due to potentially toxic elements (PTEs) represents a critical threat to the global ecosystem and human health. Naturally abundant resources have significant advantages as adsorbent materials for environmental remediation over manufactured materials such as nanostructured materials and activated carbons. These advantages include cost-effectiveness, eco-friendliness, sustainability, and nontoxicity. In this review, we firstly compare the characteristics of representative adsorbent materials including bentonite, zeolite, biochar, biomass, and effective modification methods that are frequently used to enhance their adsorption capacity and kinetics. Following this, the adsorption pathways and sites are outlined at an atomic level, and an in-depth understanding of the structure-property relationships are provided based on surface functional groups. Finally, the challenges and perspectives of some emerging naturally abundant resources such as lignite are examined. Although both unamended and modified naturally abundant resources face challenges associated with their adsorption performance, cost performance, energy consumption, and secondary pollution, these can be tackled by using advanced techniques such as tailored modification, formulated mixing and reorganization of these materials. Recent studies on adsorbent materials provide a strong foundation for the remediation of PTEs in soil and water. We speculate that the pursuit of effective modification strategies will generate remediation processes of PTEs better suited to a wider variety of practical application conditions.

Effect of Natural Sorbents in the Diet of Fattening Pigs on Meat Quality and Suitability for Processing

The effect of three natural sorbents added to the diet of pigs on the composition and physicochemical properties of two skeletal muscles-the musculusLongissimuslumborum (MLL) and musculussemimembranosus (MSM) of crossbred pigs were evaluated. The experiment was carried out on a farm in two production cycles. The addition of biochar (trial 1) significantly influenced instrumental color parameters, shear force and energy, and the oxidative stability of the skeletal muscles, while the proximate composition, pH, texture, and water-holding capacity (WHC) parameters did not differ significantly between groups in either of the two muscles. Similarly, no statistical differences were noted in the proximate chemical composition, texture parameters, or WHC of the meat in trial 2. The addition of both sorbents was associated with a significantly (p ≤ 0.01) lower content of haem pigments in the MLL and MSM, which was accompanied by a significantly (p ≤ 0.05) higher lightness (L*). Moreover, the MLL muscle of the pigs had higher oxidative stability, as well as lower drip loss (DL). In turn, the MSM of pigs had a significantly lower pH compared to the control group, however, the ultimate pH (48 h) in all groups was within the acceptable range (5.50-5.80). Summing up, the sorbents used are a safe ingredient in the diet of pigs, however, there is a need to continue and strengthen this line of research, including the relationships linking the future production goals of pig farming and processing potential in the meat industry with current climate policy.

The utilization of bentonite enhanced termite mound soil mixture as filter for the treatment of paint industrial effluent

This research investigates the applicability of bentonite enhanced termite mound soil mixture as an alternative filter medium for paint industrial wastewater (PIWW) management in a constructed pilot-scale filtration tank with four different sections. The mixture of bentonite (BC) and termite mound soil (MS) used as the filter was proportioned by percentage weight as (100% MS), $${\text{(5\% BC}} + {\text{95\% MS),}}$$ (5\% BC + 95\% MS), $${\text{(10\% BC}} + {\text{90\% MS),}}$$ (10\% BC + 90\% MS), $${\text{(15\% BC}} + {\text{85\% MS)}}$$ (15\% BC + 85\% MS) and placed into four sections, respectively. The filter materials were compacted, cured and subjected to wastewater loading for 30 weeks. The results obtained from the analysis of the filtrate samples revealed that filter with 15% BC content generally exhibited high and effective pollutant removal efficiencies of 51.3%, 98.9%, and 72.7% for total dissolved solids, total suspended solids, and copper, respectively, while a maximum removal efficiency of 100% was recorded for lead, chromium and cadmium. The pollutants (TDS, TSS, Pb, Cr, Cu and Cd) concentrations of the treated PIWW were below the National Environmental Standards and Regulations Enforcement Agency permissible limits for discharge. Hence, the 15% bentonite and 85% termite mound soil mixtures are recommended for the small-scale paint industries as a point of use measure for effective pollutant removal. Its application would mitigate the degradation of environmental resources caused by indiscriminate disposal of untreated effluent.

Megamerger of biosorbents and catalytic technologies for the removal of heavy metals from wastewater: Preparation, final disposal, mechanism and influencing factors

Heavy metal pollution, because of its high toxicity, non-biodegradability and biological enrichment, has been identified as a global aquatic ecosystems threat in recent decades. Due to the high efficiency, low cost, satisfactory recyclability, easy storage and separation, biosorbents have exhibited a promising prospect for heavy metals treatment in aqueous phase. This article comprehensively summarized different types of biosorbents derived from available low-cost raw materials such as agricultural and forestry wastes. The raw materials obtained are treated with conventional pretreatment or novel methods, which can greatly enhance the adsorption performance of the biosorbents. The suitable immobilization methods can not only further enhance the adsorption performance of the biosorbents, but also facilitate the process of separating the biosorbents from the wastewater. In addition, once biosorbents are put into large-scale use, the final disposal problems cannot be avoided. Therefore, it is necessary to review the currently accepted final disposal methods of biosorbents. Moreover, through the analysis of the adsorption and desorption mechanisms of biosorbents, it is not only beneficial to find the better methods to improve the adsorption performance of the biosorbents, but also better to explain the influencing factors of adsorption effect for biosorbents. Especially, different from many researches focused on biosorbents, this work highlighted the combination of biosorbents with catalytic technologies, which provided new ideas for the follow-up research direction of biosorbents. Finally, the purpose of this paper is to inject new impetus into the future development of biosorbents.

Ultrafast removal of Cu(II) by a novel hierarchically structured faujasite-type zeolite fabricated from lithium silica fume

Novel hierarchically structured Faujasite Type (FAU) zeolite was fabricated from industrial waste lithium silica fume (LSF) via hydrothermal method without the addition of templates. The FAU zeolites exhibited spherical filler morphology with maximum surface area of 372.8 m²/g, enriched microporosity (0.164 cm³/g), and abundant mesoporosity. Owing to its unique structure, the FAU zeolite allowed ultrafast diffusion and rapid trap of copper ion inside the cages of zeolite crystals, and achieved maximum removal (78.76%) of Cu(II) within the very first 2 min, with adsorption rate constant 5.46-6.27 times greater than that of mesoporous commercial zeolite (CZ) between 15 and 45 °C. The physico-chemical structures of the FAU zeolites were carefully studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier Transform Infrared Spectrometry (FT-IR), surface area analyzer (BET) and X-ray photoelectron spectroscopy (XPS). The maximum q_e toward Cu(II) achieved by FAU zeolite (i.e., Z9, S/A of 9) featuring a q_e of 94.46 mg/g at 25 °C as per calculated from Langmuir model, which is more than twice amount achieved by CZ (39.15 mg/g). Z9 also showed outstanding selectivity for Cu(II) over various coexisting ions. The saturated Z9 can be regenerated with a mild washing procedure, and the spent zeolite can be reused as effective antibacterial agent. This work proposes a cost-effective and green synthesis route for the hierarchically structured zeolite with high copper selective removal capacity from industrial waste.

Effects of temperature and inoculation ratio on methane production and nutrient solubility of swine manure anaerobic digestion

This study investigated the effects of temperature and volatile solids (VS) ratio of feedstock to inoculum (F/I ratio) on methane (CH₄) production and the solubility of nitrogen (N), phosphorus (P), cooper (Cu), and Zinc (Zn) after anaerobic digestion (AD) of swine manure. The highest cumulative CH₄ yield of 470 L/kgVS_feed was obtained with F/I ratios of 2.0 and 3.0 with mesophilic (37 °C) temperature, and methane production rate decreased with the increase of F/I ratio. As F/I ratio increased from 0.5 to 4.0, the lag phase for methane production increased from 1.02 days to 13.52 days, indicating an initial inhibition at high F/I ratios. AD increased the concentrations of ammonia, Cu and Zn in the AD effluent supernatant, while decreased total and water extractive P concentrations. The changes of ammonia, Cu, Zn, and P concentrations were more significant with the increase of F/I ratio.