Although graphite is not effective as an adsorbent in water treatment, it provides a homogenous, non-porous, carbonaceous structure that is ideal for studying fundamental adsorption mechanisms. High-purity graphite powder (C content 99.5%) was oxidized in an ozone stream, producing a near-surface oxygen content of 5.9 at.%, and was used together with the virgin material to establish adsorption isotherms for organic compounds in aqueous solutions. We examined how the aromaticity and substituents of the adsorptives affect adsorption on the model-activated carbon surface. For both virgin and oxidized graphite, the adsorption capacity for the aromatic compounds decreased in the order 1-naphthol > 2-methoxynaphthalene > naphthalene > anisole > phenol, with significant differences in the adsorption capacities of the two graphite species observed only for anisole, naphthalene, and 1-naphthol. The Freundlich constants (K_F) for the five compounds on virgin graphite were 23.9, 10.3, 5.5, 1.4, and 0.8 (nmol mg⁻¹ )/(µmol L⁻¹) ⁿ, respectively. Naphthalene and 1-naphthol were slightly more adsorbed on the virgin material, whereas oxidized graphite had marginally better adsorption properties for anisole. The results underline the importance of dispersive and π– π interactions in the adsorption of organic compounds on carbonaceous adsorbents; a second aromatic ring in 1-naphthol and 2-methoxynaphthalene greatly increased the adsorption capacity for these compounds compared with their one-ring counterparts phenol and anisole. Differences were also observed in the adsorption of compounds containing hydroxyl or methoxy substituents, which have electron-donating properties (a resonance effect) but different electron-withdrawal characteristics (caused by induction). Two amino acids occurring as zwitterions, l-tryptophan and l-tyrosine, were also tested as adsorptives. l-Tryptophan, which has a larger aromatic system, achieved higher loading on graphite, suggesting an adsorption mechanism primarily governed by dispersive and π– π interactions for these two ionic compounds as well.

Increasing environmental concerns, stricter legal requirements, and a wide range of industrial applications have led to growing demand for activated carbon worldwide. The energy-intensive production of fresh activated carbon causes significant CO₂ emissions and contributes to global competition for renewable carbon-based raw materials. Although (thermal) reactivation of spent activated carbon can drastically reduce the demand for fresh material, the reactivation process itself is still mostly based on experience and empirical knowledge locked into activated carbon companies. Despite the vast number of papers published in the field, practically relevant, systematic, and quantitative knowledge on the thermal reactivation process is barely available. This paper presents a simple and robust methodology for the development of a predictive model for the production of reactivated carbon with a defined product quality under energetically optimized conditions. An exhausted activated carbon sample was subjected to 26 reactivation experiments in a specially designed laboratory rotary kiln, whereas the experiments were planned and evaluated with statistical design of experiments. The influence of the reactivation conditions (heating rate, heating time, H₂O/N₂ volume ratio, and CO₂/N₂ volume ratio) on the specific surface area, energy consumption, yield, and adsorption capacity for diatrizoic acid were evaluated. The BET surface of the reactivated carbons ranged between 590 m²/g and 769 m²/g, whereas the respective fresh carbon had a BET surface of 843 m²/g. The adsorption capacity for diatrizoic acid measured as the maximum solid phase concentration q_m derived from the Langmuir equation varied between 24.4 g/kg and 69.7 g/kg (fresh carbon: 59.6 g/kg). It was possible to describe the dependency of the quality criteria on different reactivation parameters using mathematical expressions, whereas the response surface methodology with nonlinear regression was applied to build the models. A reactivation experiment under statistically optimized conditions resulted in energy savings up to 65%, whereas the properties of the reactivated sample were close to the predicted values.

Increasingly stringent water quality standards are forcing more water treatment facilities to implement adsorption steps. Activated carbon is efficient but has a high environmental impact due to CO₂ emissions and energy demand. Adsorbents derived from water treatment residuals offer a potential solution. In this study, a novel laboratory rotary furnace was designed to produce clay-carbon composite adsorbents from drinking water treatment residues. The process was optimized using a statistical design of experiments, representing the first comprehensive statistical analysis of the thermal activation of such residuals. Thermal activation increased the specific surface area almost tenfold (112–201 m²/g). The adsorbents were tested for removal of ibuprofen, caffeine, diclofenac (1 µg/L), and brilliant blue FCF (5 mg/L). Response surface models showed that heating rate (p < 0.003) and ramp duration (p < 0.00002) significantly influenced adsorption capacity. Mass balance calculations suggest on-site production could fully substitute activated carbon and generate surplus material.

This study investigates how two morphologically distinct microalgae, Chlorella vulgaris and Arthrospira platensis, at different growth phases, affect the adsorption of ibuprofen, caffeine and diclofenac onto two powdered activated carbons (AC1 and AC2). Dechlorinated tap water (DCTW) matrix was used with microalgae added and experiments were performed with/without prechlorination and with/without filtration through 0.45 ?m filter to assess the influence of total and dissolved algal organic matter. Organic micropollutants (OMPs) were analyzed using gas chromatography coupled with mass spectrometry. Results indicate that the effect of microalgae morphology on OMPs? removal efficiency is different for different carbons. Species and growth phase-dependent variations were observed in some cases. A. platensis in the stationary phase in the water reduced diclofenac removal by AC2 (from 99 % to range of 44?62 %), while C. vulgaris in the exponential phase reduced it to the range of 16?74 % in comparison to effectiveness of AC2 in DCTW without microalgae (99 %). Removal of uncharged caffeine remained stable, suggesting minimal influence from algal matrices or AC variability. For negatively charged ibuprofen and diclofenac the observed effects were more variable and not always consistent, likely due to limitations in experimental methodologies.

The growing global population has increased energy and food demand, leading to a higher production of waste streams such as fly ash from the energy sector and wastewater from food and beverage industries. Without proper treatment, these wastes pose significant environmental concerns. One promising strategy is to repurpose industrial byproducts for wastewater treatment. Winery wastewater, for instance, contains acidic organic compounds and alcohol that are difficult to remove using conventional methods, while large amounts of fly ash remain underutilized. This study, therefore, examines a hybrid system that combines fly ash-assisted Fenton oxidation with membrane filtration for winery wastewater treatment. The process involved sequential Fenton pre-treatment followed by lab-scale nanofiltration using a 1 kg/mol ceramic membrane (13.1 cm²). A Design of Experiments approach was applied to evaluate system performance under varying H₂O₂ dosages (10–30 mL/L), fly ash loadings (1–3 g/L), and membrane fluxes (40–80 LMH). Filtration was performed through multiple constant-flux cycles, with energy requirements ranging from 400 to 800 kWh/m³ for the flux variations calculated from the lab-scale pump operating at a constant power supply. The hybrid method showed strong performance, achieving 70% TOC removal and 90% reduction of color and iron. However, considerable membrane fouling was observed, likely due to increased retention and deposition of organic matter, iron, and fly ash during filtration.