Karel Folens

Understanding the prevalent form of platinum (Pt) based antineoplastic agents, used in chemotherapy, is of importance to develop a remediation strategy that restricts aquatic exposure. The speciation of Pt-based compounds was measured in actual patients’ urine using hydrophobic interaction liquid chromatography (HILIC) equipped with an ICP-MS detector. Carboplatin showed poor metabolization and intact excretion
11 h after administration, whereas cisplatin underwent a rapid aquation in the first 7 h. To compare, the in vitro degradation rate of cisplatin, carboplatin and oxaliplatin was determined in synthetic human urine, mimicking true environmental conditions. The fraction of intact molecules was measured at regular intervals following incubation at 37
C, resulting in degradation rate constants. The chemical stability was highest for carboplatin (k = 0.0143 ± 0.0012 /min), versus faster degradation of oxaliplatin and cisplatin by exponential decay with k1 = 0.0026 ± 0.0001 /min and k2 = 5.59 ± 0.46 x 10-6 /min, respectively. These kinetic parameters can serve as input to further expand modelling databases and improve the predictive power of speciation software to estimate eco-toxicity risks. Considering the strong residual cytotoxicity of the platinum antineoplastic molecules following renal clearance and human excretion, the
contaminants are of high environmental concern and offer potential for metal recovery using advanced treatment steps. In such water treatment processes, especially carboplatin, above all cancerostatic platinum compounds, should be addressed since it is more persistent in the aquatic environment.

The treatment and hydrometallurgical recovery of Pb from Zinc Leaching Residue (ZLR), a waste stream generated by the zinc refining process, is proposed in this work. Leaching achieved complete extraction of Pb (140 mg/g) within 24 h contact time using a 0.8 M sodium citrate solution. The batch leaching process that operates at ambient temperature results in a pregnant leachate solution of dissolved lead citrate. Pb is recovered from the dissolved organometal complex as a precipitate of PbSO4 after chemical reaction in acidic conditions that are maintained through continuous membrane electrolysis. Aside, an alkaline buffer is generated at the cell cathode to regenerate the leachate, so that the recycled lixiviant can be used in consequent leaching steps. Characterization of the final product by XRD, ICP-AES and Raman spectroscopy identified an amorphous PbSO4 phase with traces of lead citrate. The overall purity of Pb amounts 46 ± 4 %, representing a 3.3 fold concentration of ZLR. The integrated process is capable to treat ZLR sustainably. It can resolve the need for landfilling the mineral tailing and treat historic dump sites, respecting the zero-waste rationale, while also recovering raw material from a secondary source.

Critical and precious metals are essential in many modern applications. While their natural sources are depleting , one must adapt to guarantee a reliable supply by developing new and optimizing existing techniques to recover the elements from unexplored material flows. The aquatic phase is of great meaning to this issue, as migration from solid to liquid streams is ubiquitous during industrial manipulation of the raw materials. The resulting (waste) waters are characterized by low concentrations and varying chemical composition. Hence, hydrometallurgical technologies should cope with such specific system conditions and physico-chemical properties of critical and precious metals when elaborating a recovery strategy. This review provides an overview of the present status and outlook on technologies used to recover critical metals from solution, including ce-mentation, precipitation, reduction, ion exchange, solvent extraction, electrochemical methods and adsorption onto novel, sustainable materials. Special attention is given to adsorption technology, which is considered as one of the most promising metal recovery options owing to its facile implementation, low cost, high availability and high removal efficiencies even at low target metal concentrations. Key directions are suggested to tackle existing challenges in the field of resource recovery and improve the sustainability of future material cycling.

Environmental context. Platinum complexes are widely used to treat cancer; however, these compounds are also rapidly excreted in the urine of patients and can therefore enter waterways, presenting a toxic hazard to the environment. The biopolymer chitosan was found to be an effective and fast adsorbent for capturing multiple platinum complexes currently applied in medicine. This new approach using biomaterials is proposed to treat such drug residues while at the same time recovering the valuable metal from urine. Abstract. The majority of platinum used in antineoplastic drugs is rapidly excreted through the urine. These residual platinum compounds are highly toxic, and may eventually reach the aquatic environment if not remediated. Furthermore, platinum is a precious metal that is also relatively scarce, and it is therefore also economically worthwhile to capture and recycle it. We propose that biomass-derived adsorbents would be effective for recovering platinum from diluted streams, including synthetic human urine. Compared with ultrapure water, the salts and small biomolecules present in urine pose additional competition for active binding on the biosorbents' surface. Chitosan, biochar, wood ash and granular activated carbon were found to effectively adsorb between 0.23 and 0.97 mg/g inorganic Pt(IV) when a minimal adsorbent dose of 10 g/L was applied. The fastest adsorption rate was observed using chitosan (k2 = 728 g/mg.min), followed by wood ash (k2 = 49.4 g/mg.min) and biochar (k2 = 6.18 g/mg.min). Substantial differences in platinum recovery were observed among inorganic Pt(IV), cisplatin, carboplatin and oxaliplatin, which indicates that the adsorbate speciation is highly important for establishing a hydrometallurgical purification technique.

Urban horticulture is gaining more and more attention in the context of sustainable food supply. Yet, cities are exposed to (former) industrial activities and traffic, responsible for emission of contaminants. Trace elements were monitored in soils located in the urban environment of Ghent (Belgium) and 84 samples of Lactuca satica L. lettuce grown on it. The effects of cultivation in soil versus trays, neighbouring traffic and washing of the lettuce before consumption were studied. The 0–30 cm top layer of soils appeared heterogenic in composition and enriched in Co, Cd, Ni and Pb within 10 m from the nearest road. Yet, no similar elevated concentrations could be found in the crops, except for As. Besides uptake from the roots, the presence of trace elements in the plants is also caused by the atmospheric deposition of airborne particulate matter on the leaf surface. Correlation analysis and principal component analysis (PCA) revealed that this latter transport pathway might particularly be the case for Pt, Pd and Rh. Concentrations of Cd did not exceed the 0.2 mg/kg (fresh weight) threshold for Cd in leafy vegetables set by the European Commission. Measurements to reduce the health risks include the washing of lettuce, which effectively reduced the number of samples trespassing the maximum Pb level of 0.3 mg/kg (fresh weight). Also, cultivation in trays resulted in a lower As content in the plants. Taking into account a vigilance on crop selection, cultivation substrate and proper washing before consumption are considered essential steps for safe domestic horticulture in urban environments.

Elevated platinum (Pt) concentrations are found in road dust as a result of emissions fromcatalytic converters in vehicles. This study investigates the occurrence of Pt in road dust collected in Ghent (Belgium) and Gothenburg (Sweden). Total Pt contents, determined by tandem ICP-mass spectrometry (ICP-MS/MS), were in the range of 5
to 79 ng/g, comparable to the Pt content in road dust of other medium-sized cities. Further sample characterization was performed by single particle (sp) ICP-MS following an ultrasonic extraction procedure using
stormwater runoff for leaching. Themethod was found to be suitable for the characterization of Pt nanoparticles in road dust leachates. The extraction was optimized using road dust reference material BCR-723, for which an extraction efficiency of 2.7% was obtained by applying 144 kJ of ultrasonic energy. Using this method, between 0.2% and 18% of the Pt present was extracted from road dust samples. spICP-MS analysis revealed that Pt in the leachate is entirely present as nanoparticles of sizes between 9 and 21 nm. Although representing only a minor fraction of the total content in road dust, the nanoparticulate Pt leachate is most susceptible to biological
uptake and hence most relevant in terms of bioavailability.

Certain specialty elements are indispensable in modern technologies for their particular properties. Yet, potential risks associated to the release of these elements at any stage, remains unknown. Therefore, the dispersion of indium (In), thallium (Tl), tantalum (Ta) and niobium (Nb) in the aquatic environment of the Scheldt estuary (Flanders, Belgium) was studied. Maximum concentrations in intertidal sediments of 101 ± 15 μg/kg for In, 481 ± 37 μg/kg for Tl, 88 ± 19 μg/kg for Ta and 1162 ± 4 μg/kg for Nb appeared on the sampling location closest to the river mouth, i.e. 57.5 km upstream. Their distribution in the intertidal sediments depends on the physicochemical sediment characteristics along the flow of the river Scheldt. The same was the case for most other metals and aluminum as their occurrence also correlated (p < 0.05) with the occurrence of In, Tl and Nb. While in general, studied elements correlate to the OM content and sulfur and phosphorus herein included, a relative enrichment of In, Tl and Nb was seen at Rupelmonde (92.0 km from the river mouth). Mainly the intertidal sediment silt fraction is capable of retaining the elements by exchanging with other ions in the mineral interlayer. Increasing salinity towards the river mouth can furthermore induce the formation of insoluble chloride species. Overall, the solubility of In, Tl, Ta and Nb appeared extremely low upon extraction of pore water from intertidal sediments saturated to 100% field capacity.

Silver is a crucial element in several fields of industry. Its removal from aqueous waste streams before discharging is essential for environmental protection. Due to the environmental toxicity of Ag, stringent discharge limits are imposed by governments. Several removal techniques exist of which coagulation-flocculation is a favourable option for reasons of robustness and limited investment costs. The objective of the present work is to optimize the coagulation-flocculation process to remove silver from industrial wastewater by a profound screening and Central Composite Design. More specifically, this study focuses on maximizing the removal of silver on the one hand, and reducing the cost of operation on the other hand. Use of Poly Aluminium Chloride (PAC) coagulant in combination with a pH-correction and an anionic polyelectrolyte as flocculant led to decreasing the wastewater’s Ag concentration from 2.50 mg/L to a residual Ag concentration of 0.027 mg/L. Application of sodium poly-acrylated aluminium chloride (Magnasol 5155) as coagulant could even reduce the Ag concentration further to 0.004 mg/L. Both coagulants are able to achieve the stringent Ag discharge standard in Flanders, Belgium (0.08 mg/L), however the latter one corresponds to a higher price sensitivity, meaning that a larger removal of Ag was achieved against the same cost of chemicals used in the recovery process. Moreover, it facilitated the formation of a sludge that is 42.4 ± 3.4 m% rich in Ag, which is extremely beneficial when recovery of the precious metal is targeted.

Palladium is used in several industrial applications and, given its high intrinsic value, intense efforts are made to recover the element. In this hydrometallurgic perspective, ion-exchange (IEX) technologies are principal means. Yet, without incorporating the chemical and physical properties of the Pd present in real, plant-specific conditions, the recovery cannot reach its technical nor economic optimum. This study characterized a relevant Pd-containing waste stream of a mirror manufacturer to provide input for a speciation model, predicting the Pd speciation as a function of pH and chloride concentration. Besides the administered neutral PdCl2 form, both positively and negatively charged [PdCln]2-n species occur depending on the chloride concentration in solution. Purolite C100 and Relite 2AS IEX resins were selected and applied in combination with other treatment steps to optimize the Pd recovery. A combination of the cation and anion exchange resins was found successful to quantitatively recover Pd. Given the fact that Pd was also primarily associated with particles, laboratory-scale experiments focused on physical removal of the Pd-containing flow were conducted, which showed that particle-bound Pd can already be removed by physical pre-treatment prior to IEX, while the ionic fraction remains fully susceptible to the IEX mechanism.

The chromium-based metal–organic framework MIL-101(Cr) served as a host for the in situ synthesis of Fe3O4 nanoparticles. This hybrid nanomaterial was tested as an adsorbent for arsenite and arsenate species in groundwater and surface water and showed excellent affinity towards As(III) and As(V) species. The adsorption capacities of 121.5 and 80.0 mg/g for arsenite and arsenate species, respectively, are unprecedented. The presence of Ca, Mg and phosphate ions and natural organic matter does not affect the removal efficiency or the selectivity. The structural integrity of the hybrid nanomaterial was maintained during the adsorption process and even after desorption through phosphate elution. Additionally, no significant leaching of Cr or Fe species was observed.

This review paper presents an overview of the available technologies used nowadays for the removal of arsenic species from water. Conventionally applied techniques to remove arsenic species include oxidation, coagulation-flocculation, and membrane techniques. Besides, progress has recently been made on the utility of various nanoparticles for the remediation of contaminated water. A critical analysis of the most widely investigated nanoparticles is presented and promising future research on novel porous materials, such as metal organic frameworks, is suggested.

Abstract Platinum (Pt) based antineoplastics are important in cancer therapy. To date the Pt which is urinary excreted by the patients ends up in wastewater. This is disadvantageous from both an economic as from an ecological point of view because Pt is a valuable material and the excretion products are toxic for aquatic organisms. Therefore, efforts should be made to recover the Pt. The urinary excretion of Pt from two antineoplastics are taken under consideration, i.e. cisplatin and carboplatin. Using these reference compounds, a scenario analysis based on administration statistics from Ghent University Hospital in combination with compartmental models for urinary Pt excretion was performed to simulate the average Pt excretion profile during common treatment schemes. These average profiles can be used to assess the technical, social and economic feasibility of Pt-recovery from urine or wastewater. A one-compartment model is used for cisplatin, which is calibrated using the experimental data of six patients. In contrast, a two-compartment model with parameters from literature is used for carboplatin. A Global Sensitivity Analysis revealed kel, the rate constant of elimination, is the most sensitive parameter in the one-compartment model whereas Qu, the urine production rate, was the most sensitive in the two-compartment model for the Pt concentration Cu in urine and the excreted mass of Pt via urine. A GLUE uncertainty analysis showed that all experimental data are within the 95% uncertainty boundaries.