The use of paper sludge as a waste stream from industrial facilities represents a significant environmental challenge due to its quantity and heterogeneous composition. The aim of the study was to evaluate the adsorption characteristics of paper sludge in neutral mine effluents and aquatic solutions of metal ions: Cu(II), Zn(II), Cd(II), and Mn(II). The main novelty of the research is a comparison of the adsorption process in synthetically prepared aquatic solutions and neutral mine drainage from field sampling. The adsorption process of the monitored metals was evaluated in terms of adsorption capacity, parameters of the Freundlich and Langmuir adsorption isotherm, and the separation factor. The adsorption capacity of paper sludge of all metals is significantly lower in neutral mine drainage (NMD) compared to adsorption in aquatic solution. The adsorption capacity of Zn(II) in aqueous solution reaches equilibrium over time, similarly to Cu(II), with values ranging from 0.2 to 1.6 mg/g. For Cd(II), a slight increasing trend in the adsorption capacity of paper sludge is observed at higher initial concentrations (3–5 mg/L) over a contact time of 90–120 min. In general, aqueous solutions of metal ions exhibited higher adsorption capacities compared to NMD, with the highest value recorded for Cu(II) at 4.742 mg/g. As the concentration values in the original solution increased, a decline in K_R (from 268% to 137% at a C0 range of 4–20 mg/L) was observed. In the mine drainage with the addition of Zn(II), K_R values were also lower compared to those in aquatic solutions. The reduction in K_R became more pronounced with increasing initial concentration, showing a decrease of 29.9% to 38.9% at C0 levels ranging from 2 to 10 mg/L. The separation factors for Cu(II), Zn(II), and Cd(II) were lower in NMD, indicating better metal separation from real mine waters. The results confirm the potential of paper sludge as a low-cost adsorbent for the treatment of heavy metal contaminated waters.

Anthropogenic activities cause the accumulation of pollutants in the aquatic environment. Conventional wastewater treatment plants do not completely remove emergent pollutants, including personal care products, in which the surfactants are an essential ingredient. The results of our study confirm the presence of the surfactants in the aquatic environment, which represents an ecological and environmental risk. It was confirmed by ecotoxicological tests (test with using Daphnia magna and Lemna minor) and the specified content of the surfactants in the samples. The content of the surfactants in personal care products is significant and their impact on the aquatic environment is not sufficiently monitored. Root wastewater treatment plants, as innovative cleaning methods, represent effective cleaning methods, which can be used as a separate object or as an object for further cleaning already cleaned water from conventional wastewater treatment plants. Purified water from these devices can be recycled and used again as utility water (according to the model presented in the article). A significant benefit from the point of view of global warming and the effect of anthropogenic activity is the saving of drinking water as a natural resource. Root wastewater treatment plants ensure the required quality of discharged water in the aquatic environment.

In this paper, we compared the sorption of copper and zinc on three adsorbents - bentonite, zeolite, and dewatered digested sludge from a wastewater treatment plant. Sorption was carried out at 27ºC and subsequently at a reduced temperature of 10ºC and the results were compared. The reduced temperature positively affected the sorption efficiency and increased the adsorption capacity of the monolayer of each sorbent. Regardless of the temperature, the sorption progression was not linear. In the initial phase, the sorption proceeded rapidly, but after about 90 min the system reached equilibrium and the concentrations of metals in solution did not change significantly. The size of the specific surface area of the sorbents did not directly correlate with the removal efficiency of Cu2+ and Zn2+. Copper sorption by bentonite reached a level of almost 100% at reduced temperature and 80% at room temperature. The efficiency of zinc removal by bentonite was found to be 40% at reduced temperature. The efficiency of copper removal using zeolite was approximately 90% at both laboratory and reduced temperature. For bentonite and zeolite, we confirmed their good sorption properties. The sludge showed low Cu2+ sorption efficiency, but Zn2+ removal efficiency was higher than bentonite and zeolite. In both cases, the reduced temperature had a positive effect on the sorption capacity of the sludge. Sludge as a waste material could be used for heavy metal removal by modifying the sorption conditions or its modifying, which should be further investigated.

Mine effluents represent a serious environmental problem on a global scale. Therefore, the effective treatment of this water is a serious issue in the scientific field. The adsorption process seems to be one of the attractive methods, especially due to the simplicity of design, affordability or high efficiency. The latest scientific knowledge has shown that the use of waste and natural adsorbents is economical and effective. This study aimed to evaluate the efficiency of the adsorption process of natural and waste materials—zeolite, bentonite and fly ash—under the influence of temperature and modification of these adsorbents. The novelty of this study resides in an adjustment of the modification method of adsorbents compared to previous research: thermal–alkaline treatment versus hydrothermal one. Another novelty is the use of modified fly ash from biomass combustion as an adsorbent in comparison with the previously used fly ash from coal combustion. The modification of the adsorbents made the adsorption process more effective at all experimental concentrations. The characterisation of adsorbent samples was performed using X-ray diffraction (XRD). The parameters of the adsorption isotherms, Langmuir, Freundlich and Temkin, were estimated by nonlinear regression analysis. The adsorption capacity of Cu(II) of fly ash was comparable to natural adsorbents. Adsorption processes were better described by pseudo-second-order kinetics. At the end of this study, the suitability of using the adsorbents to reduce the concentration of Cu(II) in neutral mine effluents was observed in the following order at 30 °C: unmodified fly ash > modified bentonite > unmodified zeolite. At the temperatures of 20 °C and 10 °C, the same trend of the suitability of adsorbents use was confirmed: modified bentonite > modified zeolite > modified fly ash. The practical applicability of this study lies in the expansion of knowledge in the field of adsorption processes and in the improvement of waste management efficiency of heating plants not only in Slovakia, but also globally.

Possibilities of remediation of neutral mine drainage – Removal and recovery of potentially hazardous elements | Veronika Prepilková, Juraj Poništ, Marián Schwarz, Dagmar Samešová | Agricultural Journals

Organic waste from production processes is unutilised potential for the production of energy from renewable sources. The submitted paper studies the conditions of anaerobic degradation of selected waste from food industry (diary and distillery) when biogas is produced. Both types of organic waste have low pH values. Ash form municipal incineration as a material for the treatment of pH of waste was used. Except for the pH increase during anaerobic degradation, ash also serves as a source of macroelements for inoculum microorganisms. Kinetics of anaerobic biological digestion of organic material based on the change of pressure and biogas production depending on the ash addition (change of pH) of input samples was observed. Beside these tests, degradability of the waste was assessed by limiting biologically degradable ratio, BR and specific speed of degradability, q . pH values were adjusted with different amounts of ash (0.5; 1.8; 2.7 g/g of dry matter of organic material). Results of the research confirmed that the addition of optimum amount of ash has a positive effect on anaerobic degradation of organic materials.