The aim of this study is to evaluate the effects of biochar on the plant’s growth. A pot experiment was carried out in our study. Rice straw-derived biochar were charred at two heating temperatures (400 °C/800 °C) and two oxygen-limited atmospheres (CO₂/N₂), respectively. The FESEM/EDS technique (field emission scanning electron microscopy with X-ray energy-dispersive spectroscopy) was used to study soils, biochar and plant samples. FESEM images indicated that the structure of the biochar was highly heterogeneous with larger macropores, which can enhance soil porosity. Fine soil mineral particles blocked the biochar inner pores and channels after returning biochar to soil. EDS analysis indicated that the Al and Fe contents increased on the surface of biochar after their returning, which reduced the toxicity of Al and Fe in the soil. The returning straw directly inhibited the growth of leaf-used lettuce. Four returning biochar all significantly improved leaf-used lettuce growth, and the effects of biochar prepared under 400 °C and a CO₂ atmosphere were better than those prepared under 800 °C and a N₂ atmosphere. Changes of nitrogen content in the biochar before and after their returning were consistent with the improvement of soil available nitrogen, and plant growth was positively correlated with the nitrogen content of biochar. This study explored the impact of biochar on soil nutrients and revealed the mechanism of biochar returning to the field to promote plant growth. It is of great significance in studying and improving the characteristics of soil nutrients.

The black-odor phenomenon in polluted urban rivers is a serious environmental problem that has received increasing attention in the recent years. The low redox potential (less than − 100 mV) in the sediment is considered to be the key factor causing the occurrence of black-odor phenomenon. Here, we studied the structure and function of the microbial community during the remediation of urban rivers. Results showed a clear improvement in water quality after undergoing river remediation processes. The on-site treatments showed a succession in the microbial composition and their predicted functions. The primary iron- and sulfur-reducing bacteria (Thiobacillus, Sulfuricurvum, and Sulfursoma) and the related reactions rapidly decreased after the dredging treatment but reappeared after a year. The structure and abundance of nitrogen and methane participants were also affected by river remediation process. These results indicated that although the water quality temporarily improved shortly after a dredging process, a recurrence of the black-odor phenomenon may occur as a result of the rebound in the microbial communities.

The presence of phosphorus in water is a major cause behind the eutrophication of the aquatic environment. The growing trend focuses on the use of agriculture waste to fabricate biosorbents with higher removal capabilities for phosphate present in wastewater. Herein, a novel adsorbent named multifunctional biochar (MFBC) was applied for the decontamination of both phosphate and cadmium through two-stage adsorption. The as-prepared MFBC was characterized by TEM, BET, XPS, FTIR, and Raman spectroscopy techniques to confirm the successful grafting and presence of multiple functionalities with both amino and carboxylic functional groups on biochar (BC) surface after chemical modification route was applied. The saturated uptake capacity of phosphate that reached 57.50 mg P g⁻¹ for MFBC was noticed within 75 min at pH 5.0 and 20 °C. Based on the results obtained from adsorption kinetics and isotherm studies, as well as XPS analysis, it was interpreted that the phosphate removal was due to physical electrostatic interaction developed between protonated amino groups (–NH₃⁺) and anionic phosphate. The as-obtained multifunctional biochar loaded with phosphate (MFBC-P) demonstrated efficient cadmium ion (Cd²⁺) uptake up to 61.40 mg g⁻¹ when it was further applied for second-stage adsorption in aqueous solution. Both residual carboxylic group and phosphate loaded on MFBC-P surface were responsible for Cd²⁺ sorption. Further XRD analysis revealed that cadmium was immobilized in the form of Cd (H₂PO₄)₂ and CdCO₃. In the binary solution system, the synergistic effects between phosphate and Cd²⁺ ions were monitored such as phosphate removal increases from 91.25 to 95.40% in the presence of Cd²⁺ ions as well as the remarkable enhancement from 36.11 to 83.76% in Cd²⁺ ion uptake value noticed for coexisting phosphate ions when MFBC was tested. The study shows that BC incorporated with multiple functionalities can provide attractive applications for environmental purification.

The development of new materials and technologies for effective treatment of liquid radioactive waste is an urgent task. In present work, the novel Ti-Ca-Mg phosphate sorbents were developed. Sorbents were characterized by X-ray diffraction (XRD), Fourier transmittance infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and N₂ adsorption-desorption techniques. The influence of the chemical composition of mixed Ca-Mg-Ti phosphate sorbents and solution pH and the nature of the radionuclide on the sorption efficiency of ¹³⁷Cs, ⁸⁵Sr, and ⁶⁰Co radionuclides were determined. The obtained materials demonstrated excellent affinity towards ¹³⁷Cs, ⁸⁵Sr, and ⁶⁰Co radionuclides (Kd reached up to 10⁵ mL g⁻¹). For all Ti-Ca-Mg phosphates, an increase in the sorption efficiency of ¹³⁷Cs with an increase in the titanium content was observed. It was shown that the samples of Ti-Ca-Mg phosphates containing of 33–60 wt% titanium effectively removed ¹³⁷Cs, ⁹⁰Sr, and ⁶⁰Co radionuclides at pH 8.0–11.0. The prepared Ti-Ca-Mg phosphate sorbents are promising for one-stage treatment of aqueous solutions of complex composition from ¹³⁷Cs, ⁸⁵Sr, and ⁶⁰Co radionuclides and could be used for development of advanced technology for liquid radioactive waste treatment.

Dissolved organic matter (DOM) will be increasingly monitored by means of in situ fluorescence spectroscopy devices in order to supervise wastewater treatment plant efficiency, due to their ease of implementation and high-frequency measurement capacity. However, fluorescence spectroscopy measurements are reported to be sensitive to the sample matrix effects of temperature, the inner filter effect (IFE), and turbidity. Matrix effect estimation tests and signal correction have been developed for DOM (tyrosine-like, tryptophan-like, and humic substances-like fluorescent compounds) fluorescence measurements in unfiltered urban sewage samples. All such tests are conducted in temperature, absorbance, and turbidity ranges representative of urban sewage. For all fluorophores studied, an average of 1% fluorescence intensity decrease per degree (°C) of temperature increase could be observed. Protein-like fluorescent compound signals were found to be significantly affected by turbidity (0 to 210 NTU) and IFE (absorbance 254 nm > 0.200). Only temperature needs to be corrected for humic substances-like fluorescent compounds since other effects were not observed over the studied ranges of absorbance and turbidity. The fluorescence intensity correction method was applied first to each matrix effect separately and then combined by using a sequential mathematical correction methodology. An efficient methodology for determining the matrix effect correction equations for DOM fluorescence analysis into unfiltered urban sewage samples has been highlighted and could be used for in situ fluorescence measurement devices.

The Rozália Mine, with its long mining history, could represent an environmental threat connected with metal contamination and associated antibiotic tolerance. Metal and antibiotic tolerance profiles of heterotrophic, cultivable bacteria isolated from the Rozália Gold Mine in Hodruša-Hámre, Slovakia, and the surrounding area were analysed. Subsurface samples were collected from different mine levels or an ore storage dump. As expected, heterotrophic cultivable bacteria showed high minimum inhibitory concentrations for metals (up to 1000 mg/l for zinc and nickel, 2000 mg/l for lead and 500 mg/l for copper). Surprisingly, very high minimum inhibitory concentrations of selected antibiotics were observed, e.g. > 10,000 μg/ml for ampicillin, up to 4800 μg/ml for kanamycin, 800 μg/ml for chloramphenicol and 50 μg/ml for tetracycline. Correlation analysis revealed a linkage between increased tolerance to the antibiotics ampicillin and chloramphenicol and metal tolerance to nickel and copper. A correlation was also observed between tetracycline-kanamycin tolerance and zinc-lead tolerance. Our data indicate that high levels of antibiotic tolerance occur in deep subsurface microbiota, which is probably connected with the increased level of metal concentrations in the mine environment.

Sorption is an effective process for the remediation of mine water with low metal concentrations. To identify promising low-cost organic sorbents for nickel (Ni), adsorption and retention properties of peat, compost, brown algae, sawdust, and wood ash were compared. Batch adsorption and desorption experiments were conducted at pH 7 in 0.05 M NaNO₃ solutions to simulate the ionic strength and pH of a contaminated neutral drainage. Results of adsorption kinetic experiments were best represented by the Elovich model and the fastest rates were obtained with peat (796,075 mg g⁻¹ min⁻¹) and compost (791 mg g⁻¹ min⁻¹). Results of equilibration adsorption experiments were fitted to Langmuir and Freundlich isotherms and the highest adsorption capacities were observed for peat (around 22 mg g⁻¹) and compost (around 9 mg g⁻¹). Desorption experiments revealed that peat and compost adsorbed more Ni and also released a lower percentage of the adsorbed metal upon exposure to Ni-free solutions.

Composting has various benefits to achieve sustainability, such as substituting the use of fertilizers and preventing organic residues from being dumped in landfills. Thus, the objective was to evaluate nutrient and heavy metal release dynamics during composting with different mixtures of organic residues containing food wastes. The study was conducted in a community association in Mossoró, Rio Grande do Norte, Brazil, and the chemical analysis was carried out at the Universidade Federal Rural do Semi-Árido. Proportions between bovine manure (BM) and food wastes (FW) were Pile 1–0:3 (0% BM and 30% FW); Pile 2–1:2 (10% BM and 20% FW); Pile 3–1:1 (15% BM and 15% FW); Pile 4–2:1 (20% BM and 10% FW); Pile 5–3:0 (30% BM and 0% FW) (Pile considered as control), and the remaining 70% was filled with plant residues (tree prunings). Increment of BM proportion in compost piles with FW led to increase in C mineralization, but C mineralization decreased in the pile with only tree prunings and BM. Nitrogen immobilization occurred only in the pile with 15% BM and 15% FW; in the others, N was mineralized. Food wastes showed greater amounts of potentially mineralizable K fractions. For the micronutrients copper and zinc, in general, the initial contents decreased, whereas iron contents increased. The contents of all heavy metals diminished in the final product of the composting process, with no risk of contamination.

The palm (Elaeis guineensis), known as dendê, is an important oleaginous Brazilian plant with a high performance of oil production. In this work, a 2³ full experimental design was performed and the response surface method (RSM) was used to indicate the optimum parameter of caffeine adsorption on Elaeis guineensis endocarp activated carbon, since the endocarp is the main by-product from dendê oil production. It was set the adsorbent point of zero charge (pHₚzc), and the material was characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The RSM results indicate removal efficiency (%) at the optimal conditions, 0.20 g of adsorbent, and caffeine initial concentration of 20 mg/L, and acidic medium was about 95%. Based on ANOVA and F test (Fcₐₗcᵤₗₐₜₑd > Fₛₜₐₙdₐᵣd), the mathematical/statistical model obtained fits well to the experimental data. The overall kinetic studies showed time was achieved after 5 h and caffeine adsorption followed the pseudo-second-order model suggesting chemisorption is a predominant mechanism. Redlich-Peterson and Sips models best represented the experimental data (0.967 < R² < 0.993). Thermodynamic revealed that caffeine adsorption was spontaneous at all temperatures studied, exothermic, and probably with changes in the adsorbate-adsorbent complex during the process. The tests conducted in different water matrixes corroborate the suitability of this adsorbent to be used in caffeine removal even in a complex solution.

The efficiency of xylano-pectinolytic enzymes, co-produced by a single microbial strain Bacillus pumilus, was analysed for the recycling of mixed office waste paper through deinking and compared with the alkaline chemical deinking method. Enzymes showed maximum deinking at pH 8.5, pulp consistency of 10%, xylanase-pectinase dose of 12 and 4 IU per gram pulp, respectively, after 120 min of deinking period, and temperature at 50 °C. A chemi-enzymatic approach was employed with xylano-pectinolytic enzymes and various concentrations of deinking chemicals, which showed that enzyme-treated mixed office waste pulp requires only 40% chemicals for deinking, in order to get the almost same level of various handsheets properties, as obtained by the chemical method with 100% chemicals. Similarly, the effluent load of BOD and COD contents was also decreased by 17.90 and 19.75%. This combinational approach of deinking significantly improved the various properties of the handsheets and resulted in gain of 7.5, 9.38, 6.33 and 11.65% in tear factor, burst factor, breaking length and viscosity of the handsheets, while the effective residual ink concentration analysis of deinked handsheets of mixed office waste paper showed deinking efficiency of 22.45%, which revealed the removal of ink particles during enzymatic deinking steps.