Browsing by Subject "HEAVY-METALS"

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  • Heiskanen, Juha; Hagner, Marleena; Ruhanen, Hanna; Maekitalo, Kari (2020)
    Mine closures require landscape reclamation to reduce the environmental risks of tailings fields. However, information about the feasibility of recyclable waste materials as a growth medium layer for the cover systems of mine tailings and their effects on vegetation restoration and reforestation success is scant especially in the boreal climate. This study examines the use of various recyclable by-products in improving vegetation success on reclaimed mine tailings. The physical and chemical properties of two wood biochar types, fibre clay, compost, tailings soil and forest till soil as well as their effects as growth media on the growth of several plant species during one growing period in a greenhouse were examined. Marked differences in the properties (e.g. pH, element concentrations, water retention) as well as in plant growth among the growth media were found. Fresh non-oxidized tailings soil showed high salt contents and electrical conductivity which together with fine soil texture provided the poorest or nonexistent plant growth. Fibre clay was the coarsest and driest material and also showed poor plant growth. Root and shoot growth was greatest in pure compost. All media without compost additive showed relatively poor growth which indicates the lack of nitrogen. The results suggest that forest till soil and biochar are the most suitable growth media for the cover systems of mine tailings when added with compost or another nitrogen source. Scots pine container seedlings, willow cuttings and sown red clover showed to be the most feasible plant species to be grown on boreal tailings covers.
  • Hagner, Marleena; Uusitalo, Marja; Ruhanen, Hanna; Heiskanen, Juha; Peltola, Rainer; Tiilikkala, Kari; Hyvonen, Juha; Sarala, Pertti; Makitalo, Kari (2021)
    In the northern boreal zone, revegetation and landscaping of closed mine tailings are challenging due to the high concentrations of potentially toxic elements; the use of nutrient-poor, glacigenic cover material (till); cool temperatures; and short growing period. Recycled waste materials such as biochar (BC) and composted sewage sludge (CSS) have been suggested to improve soil forming process and revegetation success as well as decrease metal bioavailability in closed mine tailing areas. We conducted two field experiments in old iron mine tailings at Rautuvaara, northern Finland, where the native mine soil or transported cover till soil had not supported plant growth since the mining ended in 1989. The impacts of CSS and spruce (Picea abies)-derived BC application to till soil on the survival and growth of selected plant species (Pinus sylvestris, Salix myrsinifolia, and grass mixture containing Festuca rubra, Lolium perenne, and Trifolium repens) were investigated during two growing seasons. In addition, the potential of BC to reduce bioaccumulation of metals in plants was studied. We found that (1) organic amendment like CSS markedly enhanced the plant growth and is therefore needed for vegetation establishment in tailing sites that contained only transported till cover, and (2) BC application to till soil-CSS mixture further facilitated the success of grass mixtures resulting in 71-250% higher plant biomass. On the other hand, (3) no effects on P. sylvestris or S. myrsinifolia were recorded during the first growing seasons, and (4) accumulation of metals in cover plants was negligible and BC application to till further decreased the accumulation of Al, Cr, and Fe in the plant tissues.
  • Kilpi-Koski, Johanna; Penttinen, Olli-Pekka; Väisänen, Ari O.; van Gestel, Cornelis A. M. (2019)
    The aim of this study was to determine the bioavailability of metals in field soils contaminated with chromated copper arsenate (CCA) mixtures. The uptake and elimination kinetics of chromium, copper, and arsenic were assessed in the earthworm Eisenia andrei exposed to soils from a gradient of CCA wood preservative contamination near Hartola, Finland. In soils contaminated with 1480–1590 mg Cr/kg dry soil, 642–791 mg Cu/kg dry soil, and 850–2810 mg Ag/kg dry soil, uptake and elimination kinetics patterns were similar for Cr and Cu. Both metals were rapidly taken up and rapidly excreted by Eisenia andrei with equilibrium reached within 1 day. The metalloid As, however, showed very slow uptake and elimination in the earthworms and body concentrations did not reach equilibrium within 21 days. Bioaccumulation factors (BAF) were low for Cu and Cr (
  • Hagner, M.; Romantschuk, M.; Penttinen, O. -P.; Egfors, A.; Marchand, C.; Augustsson, A. (2018)
    The present study addresses toxicological properties of metal contaminated soils, using glassworks sites in south-easternl Sweden as study objects. Soil from five selected glassworks sites as well as from nearby reference areas were analysed for total and water-soluble metal concentrations and general geochemical parameters. A battery of biotests was then applied to assess the toxicity of the glassworks soil environments: a test of phytotoxicity with garden cress (Lepidium sativum); the BioTox(TM) test for toxicity to bacteria using Vibrio fischeri; and analyses of abundancies and biomass of nematodes and enchytraeids. The glassworks-and reference areas were comparable with respect to pH and the content of organic matter and nutrients (C, N, P), but total metal concentrations (Pb, As, Ba, Cd and Zn) were significantly higher at the former sites. Higher metal concentrations in the water-soluble fraction were also observed, even though these concentrations were low compared to the total ones. Nevertheless, toxicity of the glassworks soils was not detected by the two ex situ tests; inhibition of light emission by V. fischeri could not be seen, nor was an effect seen on the growth of L. sativum. A decrease in enchytraeid and nematode abundance and biomass was, however, observed for the landfill soils as compared to reference soils, implying in situ toxicity to soil-inhabiting organisms. The confirmation of in situ bioavailability and negative effects motivates additional studies of the risk posed to humans of the glassworks villages. (C) 2017 Published by Elsevier B.V.
  • Kinnunen, Niko; Laurén, Annamari (Ari); Pumpanen, Jukka; Nieminen, Tiina M.; Palviainen, Marjo (2021)
    A 96-h laboratory experiment was conducted to assess the potential of biochar as a water protection tool for acid sulfate soil runoff. Acid sulfate soils pose a risk to water bodies due to acid, metal-rich runoff, especially in drained peatland forests. New water protection methods, such as adsorption with biochar, are needed. We investigated the capability of spruce and birch biochar to adsorb metals and reduce acidity in the water. Water from an acid sulfate site was stirred with biochar, biochar with lime, and biochar with ash. We determined water Al, S, Fe, Cu, Co, Cd, Ni, and Zn concentrations periodically, as well as pH and total organic carbon at the beginning and the end of the experiment. The studied substances are considered the most abundant and environmentally harmful elements in the acid sulfate soils in Finland. Biochar surface characteristics were analyzed with FTIR spectroscopy. Concentration changes were used to parametrize adsorption kinetics models. Biochar adsorbed metals and increased pH, but lime and ash additives did not always improve the adsorption. Spruce biochar and ash addition had generally higher adsorption than birch biochar and lime addition. The adsorption was dominated by Al and Fe at lower pH, while increasing pH improved the adsorption of Cd and Zn. The results show that biochar can increase the water pH, as well as adsorb Al, Fe, Co, Cd, Ni, and Zn. Further work could include an actual-scale biochar reactor in a laboratory and field conditions.
  • Al Bawab, Abeer; Al-Hunaiti, Afnan; Abu Mallouh, Saida; Bozeya, Ayat; Abu-Zurayk, Rund; Hussein, Tareq (2020)
    Some cultural heritage sites in Jordan are in urban areas being exposed to anthropogenic pollution. Therefore, it is important to evaluate the contamination at these sites to protect them. Here, we considered a Roman archeological site (Nymphaeum) situated in Amman. The contamination in soil, plants, and building stones did not show spatial distribution within the site. The contamination was the highest in soil (heavy metals 10(4) -10(7) ppb and sulfur similar to 3.5x10(6) ppb) whereas in plants was the least for Cr (similar to 400 ppb) and in building stones it was the least for Cu (similar to 860 ppb). The highest contamination in plants and building stones was found for Al (similar to 5x10(4) and similar to 6.2x10(5) ppb respectively). The sulfur content in plants (similar to 7.6x10(5) ppb) was higher than that in the building stones (similar to 2.3x10(5) ppb). The heavy metals and sulfur contamination in the building stones were lower than what was reported elsewhere outside Jordan.
  • Heiskanen, Juha; Ruhanen, Hanna; Hagner, Marleena (2022)
    Mine closures necessitate vegetation restoration to cover tailings fields and reduce environmental risks. Sole use of forest soil as growth medium provides only low fertility and slow plant growth especially in the harsh boreal climate conditions. This preliminary study examines the feasibility of recyclable waste materials added to forest till soil for improving vegetation success on reclaimed mine tailings. One compost type, three biochar types (Bc1-3) and two ash types (Ash1-2) were studied for physical and chemical properties as well as their effects on the growth and element accumulation of timothy (Phleum pratense L.), white clover (Trifolium repens L.) and Scot spine (Pinus sylvestris L.) during one growing period in a greenhouse. Oxidized surface tailings soil and Ash2 were the finest media components while compost and Ash1 were the coarsest. Tailings soil also had the highest salt contents and electrical conductivity, while in till soil they were at the lowest levels. Timothy and white clover germinated well in moist pure tailings soil but grew poorest in it. White clover grew poorly also in pure till soil. Best biomass growth was in the mixture of till, compost and Bc2 (from sewage sludge and woodchips). Planted pine seedlings grew relatively well in all media during the first growing season but Ash1 (from wood and peat) tended to promote height growth and pure till soil root biomass. In media containing Ash1, pine tissues accumulated B, Ca, Mg, K, Na and S. Elevated As content in tailings soil accumulated in plant shoot tissues slightly; only in the old needles of pine were As levels elevated. The results suggest that till and tailings media with compost added as a nitrogen source can promote adequate plant growth during initial growing seasons. Suitable types of biochar and ash amendments can further expedite plant establishment.
  • Arar, Sharif; Al-Hunaiti, Afnan; Masad, Mohanad H.; Maragkidou, Androniki; Wraith, Darren; Hussein, Tareq (2019)
    In this study, we performed elemental analysis for floor dust samples collected in Jordanian microenvironments (dwellings and educational building). We performed intercorrelation and cluster analysis between the elemental, polyaromatic hydrocarbon (PAH), and microorganism concentrations. In general, the educational building workshops had the highest elemental contamination. The age of the dwelling and its occupancy played a role on the elemental contamination level: older and more occupied dwellings had greater contamination. The elemental contamination at a dwelling entrance was observed to be higher than in the living room. We found exceptionally high concentrations for Fe and Mn in the educational workshop and additionally, Hg, Cr, and Pb concentrations exceeded the limits set by the Canadian Council of Ministers of the Environment. According to the cluster analysis, we found three major groups based on location and contamination. According to the enrichment factor (EF) assessment, Al, Co, Mn, Ti, and Ba had EF <2 (i.e., minimal enrichment) whereas P, S, Pb, Sb, Mo, Zn, Hg, and Cu had EF > 40 (i.e., extremely enriched). In contrast, Ca and P were geogenically enriched. Furthermore, significant Spearman correlations indicated nine subgroups of elemental contamination combined with PAHs and microbes.
  • Cai, Zongping; Sun, Yan; Deng, Yanghong; Zheng, Xiaojie; Sun, Shuiyu; Sinkkonen, Aki; Romantschuk, Martin (2022)
    This study compared electrokinetic (EK) remediation with and without interval power breaking in the removal of total and plant available cadmium (Cd) in the soil. Two laboratory experiments, i.e. EK remediation with interval power breaking (24-12 h power-on-off cycles) and conventional EK remediation (continuous power supply), with the same accumulated time (192 h) of power supply, were conducted to remove soil Cd. After the EK remediation with interval power breaking, the total Cd removal efficiency in the soil rose to 38%, in comparison to 28% after the conventional EK remediation. As for the plant available Cd, the removal efficiency was enhanced from 52 to 63%. Additionally, the electric current during the EK remediation and electric conductivity after the EK remediation were higher in the soil treated by interval power breaking, which indicated an enhanced desorption and/or migration of charged species. It further meant that the higher removal efficiency of soil Cd by interval power breaking could be related to the enhanced desorption and/or migration of Cd species. This study indicated that both conventional EK remediation and EK remediation with interval power breaking were effective methods to remove soil Cd but EK remediation with interval power breaking was more efficient.
  • Elonheimo, Hanna Maria; Mattila, Tiina; Andersen, Helle Raun; Bocca, Beatrice; Ruggieri, Flavia; Haverinen, Elsi; Tolonen, Hanna (2022)
    Chronic obstructive pulmonary disease (COPD) is a slowly developing non-communicable disease (NCD), causing non-reversible obstruction and leading to marked morbidity and mortality. Besides traditional risk factors such as smoking, some environmental substances can augment the risk of COPD. The European Human Biomonitoring Initiative (HBM4EU) is a program evaluating citizens' exposure to various environmental substances and their possible health impacts. Within the HBM4EU, eighteen priority substances or substance groups were chosen. In this scoping review, seven of these substances or substance groups are reported to have an association or a possible association with COPD. Main exposure routes, vulnerable and high-exposure risk groups, and matrices where these substances are measured are described. Pesticides in general and especially organophosphate and carbamate insecticides, and some herbicides, lead (Pb), and polycyclic aromatic hydrocarbons (PAHs) showed an association, and cadmium (Cd), chromium (Cr and CrVI), arsenic (As), and diisocyanates, a possible association with COPD and/or decreased lung function. Due to long latency in COPD's disease process, the role of chemical exposure as a risk factor for COPD is probably underestimated. More research is needed to support evidence-based conclusions. Generally, chemical exposure is a growing issue of concern, and prompt action is needed to safeguard public health.
  • Kouzi, Afamia; Puranen, Matti; Kontro, Merja H. (2020)
    Biogas production from sewage sludge volatile solids (VS) by anaerobic digestion slows down towards the end of the process, among inhibitory factors being pH increase upon ammonia accumulation, poorly digestible biomaterials, and high fixed solid (FS) content. The possibility of concentrating the digested sludge VS (41.7-56.6% on a dry weight basis) by surface and bottom layer separation with biogas post-production was studied. Furthermore, the potential to recycle concentrated VS and digested sludge back to the process after adjusting pH 7.0 to optimal for biogas-producing microbes and after acid, alkali, thermal, and sonolytic treatments was examined. In general, pH 7.0 control alone improved biogas production from the recycled digested sludge the most. An equally good improvement in biogas production was achieved by recycling the digested sludge, which had been heated until ammonia had evaporated and the pH dropped to 7.0 (1-2 h, 75 degrees C), and at the same time, VS was degraded. The biogas production from the sonicated and recycled sludge was almost as good as from the pH-adjusted, or heat-treated recycled sludge. After the acid and base treatments of the digested sludge, the recycled sludge yielded often the lowest biogas volume, as the added chemicals increased the FS concentration, which proved to be a more important inhibitory factor than poorly degradable VS. The high FS content significantly reduced the benefits of the treatments. By separating the surface and bottom layers with biogas post-production, the surface layer of VS was concentrated to 51.6-61.8%, while different compositions of the layers affected the biogas production.
  • Hartikainen, E. Samuel; Lankinen, Pauliina; Rajasärkkä, Johanna; Koponen, Hilkka; Virta, Marko; Hatakka, Annele; Kähkönen, Mika A. (2012)
  • Cai, Zongping; Sun, Yan; Deng, Yanghong; Zheng, Xiaojie; Sun, Shuiyu; Romantschuk, Martin; Sinkkonen, Aki (2021)
    Electrokinetic (EK) remediation has been widely studied at laboratory scales. However, field-scale research is far less. In this study, a 14-day EK remediation was carried out, in a field pilot (4 m2) test and a full-scale (200 m2) application for the first time, in a cadmium (Cd) contaminated paddy agricultural field near a mining area. A low voltage of 20 V was applied at both scales; voltage gradient was 20 V m & minus;1 and 4 V m & minus;1 at the pilot and full scales, respectively. Samples were taken from near the anode and cathode, and in the middle of the electric field, in the soil layers 0-10 cm, 10-20 cm, and 40-50 cm. After the EK remediation, a significant portion of the total Cd was removed in all the layers at the pilot scale, by 87%, 72%, and 54% from the top down, but only in the 0-10 cm layer at the full scale by 74%. As for the plant available (exchangeable and soluble) Cd, significant removal (64%) was only observed in the 0-10 cm layer at the pilot scale. The percentage reduction of the electrical conductivity and removal efficiency of the total Cd was higher near the anode than the cathode. The soil pH was elevated near the cathode but stayed below pH 6 due to the sufficient supply of lactic acid. After the EK remediation, the concentration of the total Cd dropped below the hazard threshold, i.e. 0.4 mg (kg dry wt soil)& minus;1 for agricultural paddy fields in China. A total energy of 2 kW & middot;h and 0.6 kW & middot;h was consumed at the pilot and full scales, respec-tively. This study showed a successful in situ EK remediation of Cd contaminated paddy agricultural soil, espe-cially in the surface layer, with low voltage and energy demand. (c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (
  • Liu, Miao; Wang, Yuting; Liu, Xiucheng; Korpelainen, Helena; Li, Chunyang (2021)
    In this study, we intended to investigate the responses of rhizospheric bacterial communities of Populus cathayana to excess Zn under different planting patterns. The results suggested that intersexual and intrasexual interactions strongly affect plant growth and Zn extraction in both sexes, as well as rhizosphere-associated bacterial com-munity structures. Females had a higher capacity of Zn accumulation and translocation than males under all planting patterns. Males had lower Zn accumulation and translocation under intersexual than under intrasexual interaction; the contrary was true for females. Females harbored abundant Streptomyces and Nocardioides in their rhizosphere, similarly to males under intersexual interaction, but differed from single-sex males under excess Zn. Conversely, intersexual interaction increased the abundance of key taxa Actinomycetales and Betaproteobacteria in both sexes exposed to excess Zn. Males improved the female rhizospheric microenvironment by increasing the abundance of some key tolerance taxa of Chloroflexi, Proteobacteria and Actinobacteria in both sexes under excess Zn in intersexual interaction. These results indicated that the sex of neighboring plants affected sexual differences in the choice of specific bacterial colonizations for phytoextraction and tolerance to Zn-contaminated soils, which might regulate the spatial segregation and phytoremediation potential of P. cathayana females and males under heavy metal contaminated soils.
  • Isomursu, Marja; Koivusaari, Juhani; Stjernberg, Torsten; Hirvelä-Koski, Varpu; Venäläinen, Eija-Riitta (2018)
    The white-tailed eagle (Haliaeetus albicilla) suffered a severe population decline due to environmental pollutants in the Baltic Sea area ca. 50years ago but has since been recovering. The main threats for the white-tailed eagle in Finland are now often related to human activities. We examined the human impact on the white-tailed eagle by determining mortality factors of 123 carcasses collected during 2000-2014. Routine necropsy with chemical analyses for lead and mercury were done on all carcasses. We found human-related factors accounting for 60% of the causes of death. The most important of these was lead poisoning (31% of all cases) followed by human-related accidents (e.g. electric power lines and traffic) (24%). The temporal and regional patterns of occurrence of lead poisonings suggested spent lead ammunition as the source. Lead shot was found in the gizzards of some lead-poisoned birds. Scavenging behaviour exposes the white-tailed eagle to lead from spent ammunition.
  • Gautam, Mukesh Kumar; Lee, Kwang-Sik; Berg, Bjorn; Song, Byeong-Yeol (2020)
    Evaluating the decomposition-based change dynamics of various elements in plant litter is important for improving our understanding about their biogeochemical cycling in ecosystems. We have studied the concentrations of major, trace, and rare earth elements (REEs) (34 elements) in green tissue litter, and soil and their dynamics in the decomposing litters of successional annual fleabane (Erigeron annuus) and silvergrass (Miscanthus sinensis). Concentrations of major and trace elements in the litter of annual fleabane were 1.02-2.71 times higher compared to silvergrass. For REEs the difference between the two litter types for elements studied was in the range of 1.02-1.29 times. Both the litters showed a general decrease in the concentrations of elements in the initial stages of decomposition (60-90 days). All the major and trace elements (except for Na) in silvergrass showed a net increase in concentration at the end of the decomposition study (48.9-52.5% accumulated mass loss). Contrastingly, a few trace elements (Mn, Mo, Sr, Zn, Sb, and Cd) in annual fleabane showed a net decrease in their concentrations. For REEs, there was an increase in concentrations as well as in net amounts in both litter types. Similarities observed in the dynamics together with high and significant correlations among them likely suggest their common source. The higher concentrations of REEs in soil likely suggest its role in the net increase in REEs' concentrations and amount in litter during decomposition. (C) 2020 Elsevier B.V. All rights reserved.
  • Ruiz, Sandra R.; Eeva, Tapio; Kanerva, Mirella; Blomberg, Anna; Lilley, Thomas M. (2019)
    Metal elements, ubiquitous in the environment, can cause negative effects in long-lived organisms even after low but prolonged exposure. Insectivorous bats living near metal emission sources can be vulnerable to such contaminants. Although it is known that bats can bioaccumulate metals, little information exists on the effects of metal elements on their physiological status. For example, oxidative status markers are known to vary after detoxification processes and immune reactions. Here, for two consecutive summers, we sampled individuals from a natural population of the insectivorous bat, Myotis daubentonii, inhabiting a site close to a metal emission source. We quantified metals and metalloids (As, Ca, Cd, Co, Cu, Mn, Ni, Pb, Se, Zn) from individual fecal pellets. We measured enzymatic antioxidants (GP, CAT, SOD), total glutathione (tGSH) and ratio between reduced and oxidized glutathione (GSH:GSSG) from their red blood cells together with biometrics, hematocrit and parasite prevalence. In general, metal concentrations in feces of M. daubentonii reflected the exposure to ambient contamination. This was especially evident in the higher concentrations of Cd, Co, Cu and Ni close to a smelter compared to a site with less contaminant exposure. Annual differences were also observed for most elements quantified. Sex-specific differences were observed for calcium and zinc excretion. SOD and CAT enzymatic activities were associated with metal levels (principal components of six metal elements), suggesting early signs of chronic stress in bats. The study also shows promise for the use of non-invasive sampling to assess the metal exposure on an individual basis and metal contamination in the environment.
  • Knuutinen, Jenna; Bomberg, Malin; Kemell, Marianna; Lusa, Merja (2019)
    The uptake of nickel [Ni(II)] by Paenibacillus sp., Methylobacterium sp., Paraburkholderia sp., and Pseudomonas sp. strains isolated from a boreal bog was studied using batch experiments. All strains removed Ni(II) from the solution and the uptake efficiency was affected by the nutrient source, incubation temperature, time, and pH. As highest Ni uptake (with a maximum K-d of 1890 L/kg DW) was recorded for the Pseudomonas sp. strains, these bacteria were used in the following protein expression (SDS-PAGE and MALDI-TOFF), transmission electron microscopy (TEM) and EDS experiments. In addition, Freundlich and Langmuir sorption isotherms were determined. In the Ni(II) treated cells, dense crystalline intra-cellular accumulations were observed in TEM examinations, which were identified as Ni accumulations using EDS. SDS-PAGE and MALDI-TOFF spectra of Ni(II) treated cells showed several changes in the protein profiles, which can indicate active accumulation of Ni in these bacteria. Concurrently, we observed Ni(II) uptake to follow Freundlich and Langmuir isotherms, suggesting straight cellular biosorption in addition to the intra-cellular accumulation. The role of cellular (cell membrane and cell wall) functional groups involved in Ni(II) binding were therefore studied using Fourier transformation infrared spectroscopy. These analyses supported the potential role of the alcoholic hydroxyl, carboxyl and amine groups in Ni(II) binding in these bacteria, therefore suggesting two different Ni(II) uptake mechanisms; (i) intra-cellular accumulation [possibly connected to detoxification of Ni(II)], and (ii) straight biosorption on cell membrane/wall functional groups.
  • Seleiman, Mahmoud; Santanen, Arja; Mäkelä, Pirjo (2020)
    Background: Digested sludge is a good source of plant nutrients. However, depending on the feedstock, it might contain heavy metals, metalloids, organic compounds, pathogens, and pharmaceuticals, which can cause adverse effects on crop growth and contaminate the groundwater, soil, and food chain. Scope: The aim of this review is to focus on the potential risks of inorganic and organic contaminants to plant growth, soil, groundwater, and consequently the food chain and environment related to the utilization of digested sludge as a fertilizer on cropland. Conclusions: Inorganic compounds, such as metals and metalloids, in sludge can occasionally cause reductions in soil microbial biomass. In general, the uptake of metals and organic contaminants does not appear to cause a significant hazard to the plants and the concentrations do not surpass the maximum values allowed in soil. Organic compounds, harmful for human health or the environment, are to a large extent decomposed or volatilized from the land treated with sludge, which decreases their leaching into the environment. Many of the organic compounds are lipophilic and can be bound to soil organic matter. In conclusion, the application of sludge on cropland might be a sustainable management practice; however, further investigations are needed to determine the accumulation and persistence of possible hazardous emerging chemicals and pathogens in the environment and formation of harmful intermediate reaction of inorganic and organic compound products.
  • Venäläinen, Salla H.; Hartikainen, Helinä (2018)
    Treatment of acidic mining water (MW) with industrial minerals and alkaline chemicals requires utilisation of unrenewable raw materials and produces disposable inorganic sludges of no further use. We investigated the efficiency of bio-based anionic nanofibrillated cellulose (NFC) to purify authentic MW high in metals and sulphate. In a short-term (10 min) adsorption experiment, highly acidic (pH 3.2) multi-metal process water was treated with anionic NFC gels differing in their consistency (1.1%, 1.4% and 1.8% wow) at three sorbent-to-solution ratios. To unravel the purification efficiency of the NFC gels, MW was treated stepwise with a set of fresh NFC gels in three sequential batches. Each treated solution was filtrated before pH measurement and analysis for the NFC-induced changes in the metal and sulphate concentrations. All NFC gels efficiently co-adsorbed metals and sulphate and decreased the acidity of MW. Depending on the dosage, a triplicated treatment with the NFC gels removed as much as 32-75% of metal cations and 34-75% of sulphate anions. The retention of metals highly exceeded the amount of carboxyl groups in the sorbent Thus, we concluded that, instead of electrostatic adsorption, the retention took place through formation of covalent metal-NFC complexes. The subsequent surplus in positive total charge formed on the NFC-surface, in turn, enabled electrostatic co-adsorption of sulphate anions. The mutual interactions between cellulose nanofibrils in the NFC gel weakened with decreasing consistency, which promoted the accessibility of the sorption sites. This improved the purification efficiency while decreasing the demand for cellulosic raw material. We concluded that anionic NFC could potentially serve as a multifunctional and resource-efficient purification agent in the treatment of acidic process waters of high ionic strength. Ideally, the elements retained could be liberated and recycled elsewhere. (C) 2018 Elsevier Ltd. All rights reserved.