Recovery of Waste Polyurethane from E-Waste—Part I: Investigation of the Oil Sorption Potential

The shredding of end-of-life refrigerators produces every year in Italy 15,000 tons of waste polyurethane foam (PUF), usually destined for energy recovery. This work presents the results of the investigation of the oil sorption potential of waste PUF according to ASTM F726–17 standard. Three oils (diesel fuel and two commercial motor oils) having different densities (respectively, 0.83, 0.87, and 0.88 kg/dm3) and viscosities (respectively, 3, 95, and 140 mm2/s at 40 °C) were considered. The waste PUF was sampled in an Italian e-waste treatment plant, and its characterization showed 16.5 wt% particles below 0.71 mm and 13 wt% impurities (paper, plastic, aluminum foil), mostly having dimensions (d) above 5 mm. Sieving at 0.071 mm was applied to the waste PUF to obtain a “coarse” (d > 0.71 mm) and a “fine” fraction (d < 0.71 mm). Second sieving at 5 mm allowed an “intermediate” fraction to be obtained, with dimensions between 0.71 and 5 mm. The oil sorption tests involved the three fractions of waste PUF, and their performances were compared with two commercial oil sorbents (sepiolite and OKO-PUR). The results of the tests showed that the “fine” PUF was able to retain 7.1–10.3 g oil/g, the “intermediate” PUF, 4.2–7.4 g oil/g, and the “coarse” PUF, 4.5–7.0 g oil/g, while sepiolite and OKO-PUR performed worse (respectively, 1.3–1.6 and 3.3–5.3 g oil/g). In conclusion, compared with the actual management of waste PUF (100 wt% sent to energy recovery), the amount destined directly to energy recovery could be limited to 13 wt% (i.e., the impurities). The remaining 87 wt% could be diverted to reuse for oil sorption, and afterward directed to energy recovery, considered as a secondary option.

Screening on the sorption of emerging contaminants to polystyrene and polyethylene and use of coagulation – flocculation process for microplastics’ removal

<p>In this study, preliminary experiments were conducted to investigate the sorption potential of different organic micropollutants to polystyrene and polyethylene and to examine the removal efficiency of these microplastics during coagulation experiments with iron and manganese coagulants. For the sorption experiments, eight synthetic chemicals which belong to three different categories, pharmaceutical compounds, personal care products and endocrine-disrupting compounds were used. Among target compounds, important removal due to sorption to microplastics was noticed for the antihypertensive drugs Valsartan and Losartan, when polystyrene was used as sorbent material. Their sorption was a slow and gradual process; 20% of valsartan and 59% of losartan was sorbed after 168 h. On the other hand, no sorption of parabens, bisphenol A and sulfamethoxazole was observed. The elaboration of coagulation experiments showed that polystyrene is removed to a higher percentage comparing to polyethylene, reaching 92.4% and 72.1%, respectively. The higher removal of polystyrene was achieved when ferrous sulfate or magnesium sulfate was added, while the use of ferric chloride did not improve its removal. Increased removal of polyethylene was achieved when magnesium sulfate was used. Further experiments should be conducted to investigate the parameters affecting sorption of valsartan and losartan to microplastics and the mechanisms governing removal of polystyrene and polyethylene during coagulation.</p>

Insight into the Sorption of 5-Fluorouracil and Methotrexate onto Soil–pH, Ionic Strength, and Co-Contaminant Influence

Nowadays anticancer drugs (ADs), like other pharmaceuticals, are recognized as new emerging pollutants, meaning that they are not commonly monitored in the environment; however, they have great potential to enter the environment and cause adverse effects there. The current scientific literature highlights the problem of their presence in the aquatic environment by publishing more and more results on their analytics and ecotoxicological evaluation. In order to properly assess the risk associated with the presence of ADs in the environment, it is also necessary to investigate the processes that are important in understanding the environmental fate of these compounds. However, the state of knowledge on mobility of ADs in the environment is still very limited. Therefore, the main aim of our study was to investigate the sorption potential of two anticancer drugs, 5-fluorouracil (5-FU) and methotrexate (MTX), onto different soils. Special attention was paid to the determination of the influence of pH and ionic strength as well as presence of co-contaminants (cadmium (Cd2+) and another pharmaceutical—metoprolol (MET)) on the sorption of 5-FU and MTX onto soil. The obtained distribution coefficient values (Kd) ranged from 2.52 to 6.36 L·kg−1 and from 6.79 to 12.94 L·kg−1 for 5-FU and MTX, respectively. Investigated compounds may be classified as slightly or low mobile in the soil matrix (depending on soil). 5-FU may be recognized as more mobile in comparison to MET. It was proved that presence of other soil contaminants may strongly influence their mobility in soil structures. The investigated co-contaminant (MET) caused around 25-fold increased sorption of 5-FU, whereas diminished sorption of MTX. Moreover, the influence of environmental conditions such as pH and ionic strength on their sorption has been clearly demonstrated.

Nitrogen enrichment of animal bone-derived biochars as an agricultural NP-fertilizer

&lt;p&gt;Food processing creates many by-products, and not all of them are used efficiently. Especially animal-based side products are frequently considered as waste with costly disposal requirements. For recycling of the nutrients contained in these residues, also under consideration of the hygienic specifications, pyrolysis can be used to create animal bone-based biochars. A lab-scale pyrolysis reactor (Pyreka 3.0) was used to produce biochars from different bone fractions of cattle and pigs after these bones had originated as waste from abbatoir operations. This study had the objective to investigate the potential of the bone chars to serve as a phosphorus (P) supply for agricultural purposes and to study the ammonium sorption potential of these chars.&lt;/p&gt;&lt;p&gt;The total phosphorus content of bones reached up to 140 mg/g. The water-soluble phosphorus content was in the range of 0.16 &amp;#8211; 0.93 mg/g, an increase in pyrolysis temperature from 350 &amp;#176;C to 500 &amp;#176;C or 650 &amp;#176;C increased the water-soluble content by 13.3 or 12.2 % respectively. The citric acid soluble phosphorus content was between 1.75 &amp;#8211; 2.19 mg/g. After pyrolysis temperatures of 350 &amp;#176;C, slightly more phosphorus dissolved in the coal products than at 500 &amp;#176;C (+2.7 %) and at 650 &amp;#176;C (+5.5 %).&lt;/p&gt;&lt;p&gt;The ammonium sorption capacity of biochars produced by varying pyrolytic processes was investigated by a series of sorption experiments. The removal of ammonium by the biochars from an aqueous ammonium solution was measured by using colorimetric determination of the ammonium content. The maximum ammonium sorption results were achieved by biochars produced from bovine heads and feet respectively at a temperature of 900&amp;#176;C and activated with H&lt;sub&gt;2&lt;/sub&gt;O.&lt;/p&gt;&lt;p&gt;When exposed to a solution containing 50 mg/L of ammonium, these biochars adsorbed 1.23 and 1.14 mg ammonium/g biochar, respectively. The possibility to enrich abattoir waste biochars, which are depleted in nitrogen because of the pyrolysis process, with ammonium gained from a nitrogen-enriched biogas slurry produced from animal residues of the meat production process was tested using a substitute slurry made with ammonium sulfate. The highest absorbance rate using the substitute slurry containing 10 g/L ammonium was achieved by biochar made from bovine heads and resulted in 43.1 mg ammonium/g biochar.&lt;/p&gt;&lt;p&gt;This study shows that bone-based biochars enriched with nitrogen from e.g. biogas digestates have significant potential as an NP-fertilizer that supports the strategies of circular economy.&lt;/p&gt;

How much carbon can be added to soil by sorption?

Quantifying the upper limit of stable soil carbon storage is essential for guiding policies to increase soil carbon storage. One pool of carbon considered particularly stable across climate zones and soil types is formed when dissolved organic carbon sorbs to minerals. We quantified, for the first time, the potential of mineral soils to sorb additional dissolved organic carbon (DOC) for six soil orders. We compiled 402 laboratory sorption experiments to estimate the additional DOC sorption potential, that is the potential of excess DOC sorption in addition to the existing background level already sorbed in each soil sample. We estimated this potential using gridded climate and soil geochemical variables within a machine learning model. We find that mid- and low-latitude soils and subsoils have a greater capacity to store DOC by sorption compared to high-latitude soils and topsoils. The global additional DOC sorption potential for six soil orders is estimated to be 107 $$\pm$$ ± 13 Pg C to 1 m depth. If this potential was realized, it would represent a 7% increase in the existing total carbon stock.

Phosphorus sorption potential of natural adsorbent materials from a Brazil semiarid region to control eutrophication

Aim The aim of the present study was to evaluate the potential soluble reactive phosphorus (SRP) sorption of three natural P adsorbents (Luvisol, Planosol, and Scheelite tailing) from Brazil’s semiarid region. Methods The adsorption tests were done under pH 8 conditions with the natural adsorbents and Lanthanum-Modified Bentonite (LMB). The effect of humic substances on SRP sorption was also tested. For this, Luvisol and Planosol were incinerated to reduce their humic components, and new adsorption tests were done. The effect of adsorbents on water pH was also evaluated. Results The SRP sorption potential of the natural adsorbents was high at pH 8. Of the natural adsorbents, Luvisol achieved the highest maximum SRP adsorption capacity (Q) of 17.5 mg g-1, followed by Scheelite tailing (8.3 mg g-1) and Planosol (7.7 mg g-1). Scheelite tailing, Planosol and LMB increased the pH of the water. After treatment to reduce humic substances, Planosol showed a Q of 22.3 mg g-1 while Luvisol produced 11.1mg g-1. Reducing the amount of humic substances potentiated the sorption process in the Planosol. However, the isotherms of untreated Luvisol and treated Planosol have not reached equilibrium and therefore may be overestimated. Conclusions The precipitation process was probably the main sorption mechanism, being more expressive than adsorption. Scheelite tailing was the most promising material for eutrophic environments because it is alkaline, calcium-rich, and this capacity will probably remain high under anoxic conditions. It also has a small amount of organic matter and, consequently, contains less humic substances. The quality of the clay present in natural adsorbents was more important than quantity in the sorption process.

Sorption of phenols on hexadecyltrimethylammonium- modified bentonite: Application of Polanyi−Manes potential theory

This study investigated the sorption of phenol and 4-chlorophenol (4-CP) on natural bentonite modified with hexadecyltrimethylammonium (HDTMA) cation. The Freundlich, Langmuir, Dubinin−Radushkevich (DR), Sips, and Polanyi−Dubinin−Manes (PDM) models fitted the sorption data well (R2 > 0.92). The Freundlich coefficient and the maximum sorbed amount of the Langmuir and PDM models of 4-CP were higher than phenol because of higher hydrophobicity (log Kow = 2.39 for 4-CP and 1.46 for phenol). The PDM model that includes solubility and molar volume was highly useful in predicting the sorption of phenols having widely different hydrophobicity and solubility. The characteristic curves, the plot of sorbed volume ( qv) versus the sorption potential per molar volume ( ε/ Vm) of 4-CP and phenol were distinctly different although they have similar chemical compositions. The selectivity of 4-CP (3.72) was higher than that of phenol (0.27) in binary sorption systems. The sorbed volume ( qv) in the binary sorption was remarkably reduced and the characteristic curve had wider distribution owing to competition in pore-filling. The sorption behaviors were elucidated by partitioning and pore-filling mechanisms. Among the tested binary sorption models, the modified Langmuir competitive model was the best in the prediction of the binary sorption (R2 > 0.98).

How much more carbon can be sorbed to soil?

&lt;p&gt;Quantifying the upper limit of stable soil carbon storage and relative saturation is essential for guiding policies designed to increase soil carbon storage, such as &amp;#8216;4 per 1000&amp;#8217; sequestration initiative. Carbon stabilization processes are diverse, but one particular pool of carbon that is considered stable across climate zones and soil types is the mineral-associated fraction, measured using density or size fractionation. Some soil carbon decomposition models assume sorption to minerals is the main form of stabilization in this fraction. We estimate the global capacity of mineral soils in six soil orders to sorb additional dissolved organic carbon (DOC). We gathered data from 400 DOC sorption experiments representing 133 soil profiles across six soil orders. We used the relationship between DOC added and DOC sorbed to calibrate a modified Langmuir sorption equation, from which we quantified the DOC sorption potential in each soil. We found that the sorption potential is empirically related to climate variables (including mean annual temperature and mean annual precipitation) and soil geochemical variables (chiefly, percent clay, pH, and soil order). From this relationship, we then estimated the DOC sorption potential for 14631 profiles distributed globally. This amount was 1.4 (global median; 95% CI: 0.50, 2.8) kg C m&lt;sup&gt;-3&lt;/sup&gt;, totaling 102 Pg C globally across six soil orders, representing up to a 7% increase in the existing total C stock. We show that there is greater capacity for additional DOC sorption in subsoils (30cm-1m) compared to top-soils (0-30cm). The gap between the modest potential of mineral sorption processes found in this study and the large total capacity of long-term organic matter stabilization (2541 Pg C for the six soil orders of this study) indicates that other mechanisms such as aggregation, the sorption of microbial necromass, layering, and co-precipitation also play a critical role in stable organic matter formation and persistence.&lt;/p&gt;