Utilising highly characterised peats to remove cadmium from aqueous solutions

This research investigated the biosorption of cadmium (Cd) from aqueous solutions by six highly characterised peats. Samples of the peats were tested both in unaltered condition and after treatment with hydrochloric acid (HCl) to free up any occupied exchange sites. Other factors tested were sample dose, contact time, mixing temperature, and the concentration and pH of the Cd solution. Desorption studies were also performed, and tests were done to determine whether the peats could be re-used for Cd biosorption. The results indicate that all six peats biosorb Cd from aqueous solution well (36−100 % removal) and that their Cd removal capacities are affected by the various factors that were manipulated. The three factors that had the greatest effects on the Cd removal capacities of the peats were sample dose and the concentration and pH of the Cd solution. The percentage of Cd removed increased as the sample dose increased (16−31 % increase) and as the pH of the Cd solution increased (16−57 % increase). As the concentration of the Cd solution increased, the percentage of Cd removed increased slightly for two of the six peats (1−2 % increase) and decreased for three peats (19−23 % decrease). As the mixing temperature increased, the percentage of Cd removed increased slightly for three of the peats (1−12 % increase) and decreased slightly for the other three (1−5 % decrease). The desorption results showed a 34−71 % Cd recovery rate. Re-used peats were also highly effective at removing Cd, whether or not they had gone through desorption. Two of the six peats were slightly better at Cd removal after treatment with HCl (4−7 % better than untreated peats), while the other four peats worked better in their unaltered states (3−18 % better). As all of the peat types tested can be repeatedly re-used for additional Cd biosorption cycles, their disposal should not create a hazardous waste problem. On the other hand, using peat for any industrial purpose is increasingly disfavoured nowadays, for sustainability reasons. Thus, the results of this study might be used to identify and/or develop materials with properties similar to those of the most effective peats (i.e. artificial peats) for use as biosorbents of Cd. These materials could be agricultural waste products such as soybean or rice hulls, constructed wetlands with living plants similar to those found in the tested peats, or possibly biochar of these living plants

Biosorption of mercury from aqueous solutions using highly characterised peats

This research investigated the biosorption of mercury from aqueous solutions by six highly characterised peats. Samples of the peats were tested both in unaltered condition and after being treated with hydrochloric acid (HCl) to free up any occupied exchange sites. Other variables tested were sample dose, contact time, mixing temperature, and the concentration and pH of the mercury solution. Desorption studies were also performed, and tests were done to determine whether the peats could be re-used for mercury biosorption. The results indicate that all six peat types biosorb mercury from aqueous solutions extremely well (92−100 % removal) and that their mercury removal capacities are not significantly affected by manipulation of the various factors tested. The factor that had the greatest impact on the mercury removal capacities of the peats was the pH of the mercury solution. The optimal mercury solution pH for mercury removal was in the range 5−7 for four of the peats and in the range 2−3 for the other two. The desorption results indicate that it may be possible to recover up to 41 % of the removed mercury. All of the peat types tested can be repeatedly re-used for additional mercury biosorption cycles. Hence, their disposal should not become a hazardous waste problem

Environmental impact evaluation of olive oil wastewater shedding on cultivated fields

The olive oil industry in Europe produces a significant amount of olive mill wastewater (OMW) which poses a serious environmental threat if its disposal is not carried out correctly. At the same time, OMW is an important source of useful substances for several activities (e.g. for food, chemical and energy industries; in agriculture as a fertiliser, as a resource for organic matter). Currently in Italy OMW shedding on cultivated fields seems to be the most viable solution. Disposing of OMW appropriately requires specific data on wastewater management (OMW doses and type, the latter depending on the olive oil extraction system, and distribution modality), the shed field (soil type and features, crop typologies, agricultural practises), and the climatic pattern of the area where the field is located. All these data, considered in an integrated evaluation procedure based on the fuzzy logic theory (Sugeno technique), means that the agro-environmental risk can be assessed by calculating a synthetic index ascribable to a specific hypothesis of OMW shedding. This paper presents a multiplatform software application called ICABAS. The software has been adapted to the current Italian legislation and the specific environmental conditions of the Basilicata Region where it has been integrated into the regional laws for olive mill residue management. The evaluation procedure is easy to use and provides a useful tool for administrative and technical purposes and also to support decision systems, at a policy level, for the sustainable management of the resources involved

Biosorption of hexavalent chromium from aqueous solutions using highly characterised peats

This research investigated the biosorption of hexavalent chromium (CrVI) from aqueous solutions by six highly characterised peats. Samples of the peats were tested both in unaltered condition and after being treated with hydrochloric acid (HCl) to free up any occupied exchange sites. Other variables tested were sample dose, contact time, mixing temperature, and the concentrations and pH of the CrVI solution. Desorption studies were also performed, and tests were done to determine whether the peats could be re-used for CrVI biosorption. The results indicate that all six peat types biosorb CrVI from aqueous solution well (42–100 % removal) and that their CrVI removal capacities are affected by manipulation of the various factors. The two factors that had the greatest impact on the CrVI removal capacities of the peats were the concentrations and pH of the CrVI solution. As the CrVI solution concentration and pH were increased, the percent of CrVI removed decreased dramatically (33–56 % decrease for concentration increase; 36–45 % decrease for pH increase with four of the six peat types). The desorption results indicate that it may be possible to recover up to 5 % of the removed CrVI. All of the peat types tested can be repeatedly re-used for additional CrVI biosorption cycles. Hence, their disposal should not become a hazardous waste problem

Introducing global peat-specific temperature and pH calibrations based on brGDGT bacterial lipids

International audienceGlycerol dialkyl glycerol tetraethers (GDGTs) are membrane-spanning lipids from Bacteria and Archaea that are ubiquitous in a range of natural archives and especially abundant in peat. Previous work demonstrated that the distribution of bacterial branched GDGTs (brGDGTs) in mineral soils is correlated to environmental factors such as mean annual air temperature (MAAT) and soil pH. However, the influence of these parameters on brGDGT distributions in peat is largely unknown. Here we investigate the distribution of brGDGTs in 470 samples from 96 peatlands around the world with a broad mean annual air temperature (−8 to 27 °C) and pH (3–8) range and present the first peat-specific brGDGT-based temperature and pH calibrations. Our results demonstrate that the degree of cyclisation of brGDGTs in peat is positively correlated with pH, pH = 2.49 x CBTpeat + 8.07 (n = 51, R2 = 0.58, RMSE = 0.8) and the degree of methylation of brGDGTs is positively correlated with MAAT, MAATpeat (°C) = 52.18 x MBT5me’ – 23.05 (n = 96, R2 = 0.76, RMSE = 4.7 °C). These peat-specific calibrations are distinct from the available mineral soil calibrations. In light of the error in the temperature calibration (∼ 4.7 °C), we urge caution in any application to reconstruct late Holocene climate variability, where the climatic signals are relatively small, and the duration of excursions could be brief. Instead, these proxies are well-suited to reconstruct large amplitude, longer-term shifts in climate such as deglacial transitions. Indeed, when applied to a peat deposit spanning the late glacial period (∼15.2 kyr), we demonstrate that MAATpeat yields absolute temperatures and relative temperature changes that are consistent with those from other proxies. In addition, the application of MAATpeat to fossil peat (i.e. lignites) has the potential to reconstruct terrestrial climate during the Cenozoic. We conclude that there is clear potential to use brGDGTs in peats and lignites to reconstruct past terrestrial climate