Hydrothermal carbonization (HTC) is an energy-efficient thermochemical process for converting wet waste products into value added materials for water treatment. Understanding how HTC influences the physicochemical properties of the resultant materials is critical in optimizing the process for water treatment, where surface functionality and surface area play a major role. In this study, we have examined the HTC of four wet waste streams, sewage sludge, biosludge, fiber sludge, and horse manure at three different temperatures (180°C, 220°C, and 260°C). The physicochemical properties of these materials were examined via FTIR, SEM and BET with their adsorption capacity were assessed using methylene blue. The yield of solid material after hydrothermal carbonization (hydrochar) decreased with increasing temperature for all samples, with the largest impact on horse manure and fiber sludge. These materials also lost the highest degree of oxygen, while HTC had minimal impact on biosludge and sewage sludge. The differences here were due to the varying compositions of each waste material, FTIR identified resonances related to cellulose in horse manure and fiber sludge, which were not detected in biosludge and sewage sludge. Adsorption capacities varied between 9.0 and 68 mg g −1 with biosludge HTC at 220°C adsorbing the highest amount. Adsorption also dropped drastically at the highest temperature (260°C), indicating a correlation between adsorption capacity and HTC conditions. This was attributed to the loss of oxygen functional groups, which can contribute to adsorption. These results suggest that adsorption properties can be tailored both by selection of HTC temperature and feedstock.

In this study, we examined the photodegradation of decabromodiphenyl ether (BDE-209) on the surface of car seat covers from end-of-life vehicles (ELVs). Samples were collected at two car dismantling facilities in Sweden and cover car models from 1989 to 1998. The content of polybrominated diphenyl ethers (PBDEs) in nine real samples (fabric and polyurethane foam) was first characterized. Fabric samples that did not contain BDE-209 were then spiked with BDE-209 and irradiated in the laboratory and under sunlight. Photoproducts were identified using high performance liquid chromatography coupled to electrospray ionization mass spectrometer (HPLC-ESI-Orbitrap-MS), whereas volatile products were analyzed by gas chromatography-mass spectrometry (GC-MS). Similar photodegradation rates and oxidation products were observed in fabric samples irradiated in the laboratory and those collected from ELVs. Estimated half-life of BDE-209 on fabric inside vehicles ranged from 3 to 6 years. Thirteen major photoproducts were identified as lower brominated products, hydroxylated BDEs, brominated and hydroxylated dibenzofurans (PBDFs) and dioxins (PBDDs). Furthermore, several photoproducts were found to be transferable into water, particularly bromophenols and hydroxylated BDEs, and others into gas phase, such as bromomethanol and 1,2-dibromoethane. This should be taken into consideration for better estimating exposure to PBDEs and to develop strategies for ELV recycling.

Adsorption on low-cost biochars would increase the affordability and availability of water treatment in, for example, developing countries. The aim of this study was to identify the precursor materials and hydrochar surface properties that yield efficient removal of compounds of environmental concern (CEC). We determined the adsorption kinetics of a mixture containing ten CECs (octhilinone, triclosan, trimethoprim, sulfamethoxasole, ciprofloxacin, diclofenac, paracetamol, diphenhydramine, fluconazole, and bisphenol A) to hydrochars prepared from agricultural waste (including tomato- and olive-press wastes, rice husks, and horse manure). The surface characteristics of the hydrochars were evaluated via diffuse reflectance infrared spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS), and N2-adsorption. Kinetic adsorption tests revealed that removal efficiencies varied substantially among different materials. Similarly, surface analysis revealed differences among the studied hydrochars and the degree of changes that the materials undergo during carbonization. According to the DRIFTS data, compared with the least efficient adsorbent materials, the most efficient hydrochars underwent more substantial changes during carbonization.Electronic supplementary materialThe online version of this article (10.1007/s11356-018-1781-0) contains supplementary material, which is available to authorized users.

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In this study, we have examined how the activation of hydrothermally carbonized sewage sludge and horse manure influences the inorganic component of these materials and surface chemistry. This was examined through statistical correlations between kinetic tests using trimethoprim, fluconazole, perfluorooctanoic acid, and copper, zinc, and arsenic and physicochemical properties. Yield and inorganic content varied considerably, with potassium hydroxide–activated materials producing lower yields with higher inorganic content. Phosphoric acid activation incorporated inorganically bound phosphorus into the material, although this showed no statistically relevant benefit. A maximum surface area of 1363 m2g−1 and 343 m2g−1 was achieved for the horse manure and sewage sludge. Statistical analysis found positive correlations between carbon-oxygen functionalities and trimethoprim, fluconazole, perfluorooctanoic acid, and copper removal, while inorganic content was negatively correlated. Conversely, arsenic removal was positively correlated with inorganic content. This research provides insight into the interactions with the organic/inorganic fraction of activated waste materials for water treatment.