Spent coffee grounds (SCGs) have great potential as a useful, value-added biological material. In this context, activated carbon (AC) was prepared from SCGs by an activation process using H₃PO₄ at 600 °C in the air and used as an adsorbent for the azo dye AO7, a model molecule for dye colorants found in textile industry effluents. X-ray diffraction, SEM and BET revealed that the AC was predominantly amorphous, consisting of a powder of 20–100 µm particles with mesopores averaging 5.5 nm in pore size. Adsorption kinetics followed a pseudo-second-order law, while the Langmuir model best fitted the experimental isotherm data (maximum capacity of 119.5 mg AO7 per AC g). The thermodynamic parameters revealed that adsorption was endothermic and spontaneous. All the characterizations indicated that adsorption occurred by physisorption via mainly π–π interactions. The best experimental removal efficiency optimized by means of a Box–Behnken design and response surface methodology was 98% for an initial AO7 concentration of 20 mg·L⁻¹ at pH 7.5 with a dose of 0.285 g·L⁻¹ of AC and a contact time of 40 min. These results clearly show that activated carbon prepared from SCGs can be a useful material for efficiently removing organic matter from aqueous solutions.

Spent coffee grounds (SCG) have great potential as a useful, value-added biological material. In this context, activated carbon (AC) was prepared from SCG by an activation process using H3PO4 at 600°C in air and used as an adsorbent for the azo dye AO7, a model molecule for dye colorants found in textile industry effluents. X-ray diffraction, SEM and BET revealed that the AC was predominantly amorphous, consisting of a powder of 20-100 µm particles with mesopores averaging 5.5 nm in pore size. Adsorption kinetics followed a pseudo-second-order law, while the Langmuir model best fitted experimental isotherm data (maximum capacity of 119.5 mg AO7 per AC g). Thermodynamic parameters revealed that adsorption was endothermic and spontaneous. All the characterizations indicated that adsorption occurred by physisorption via mainly - interactions. The best experimental removal efficiency optimized by means of a Box-Behnken design and response surface methodology was 98% for an initial AO7 concentration of 20 mg.L-1 at pH 7.5 with a dose of 0.285 g.L-1 of AC and a contact time of 40 min. These results clearly show that activated carbon prepared from SCG can be a useful material for efficiently removing organic matter from aqueous solutions.

The widespread presence of stable and hazardous organic contaminants, such as synthetic dyes, in industrial effluents necessitates the development of resilient treatment strategies capable of achieving efficient degradation and decolorization of dye pollutants. Conventional treatment processes often fail to remove such recalcitrant compounds, prompting growing interest in integrated advanced systems. Photocatalytic membranes represent a promising solution due to the synergistic combination of physical separation and catalytic degradation. In this study, zinc oxide (ZnO) thin films were deposited by spin coating onto smectite–zeolite ceramic membranes (MS10/Z90), applying one (M1), two (M2), and three (M3) successive coating layers to control catalyst thickness. SEM analysis confirmed that increasing the number of layers resulted in a thicker and more homogeneous ZnO coating, while XRD revealed enhanced crystallinity and larger crystallite size. Water permeability decreased progressively from 623 L·h⁻¹·m⁻²·bar⁻¹ for the uncoated membrane to 506, 439, and 350 L·h⁻¹·m⁻²·bar⁻¹ for M1, M2, and M3, respectively. Photocatalytic performance was evaluated using Rhodamine B (RhB) (10 mg·L⁻¹) under UV irradiation (365 nm, 18 W) for 180 min, achieving degradation efficiencies of 83.0%, 94.6%, and 99.1% for M1, M2, and M3, respectively. The degradation kinetics followed a pseudo-first-order model, with rate constants increasing with catalyst layer thickness. Free radical scavenging assays confirmed that hydroxyl radicals (•OH) were the primary reactive species responsible for RhB degradation. These findings highlight the critical influence of ZnO layer thickness and mass transfer on photocatalytic performance, demonstrating the potential of ZnO-coated ceramic membranes for efficient pollutant degradation and in situ photocatalytic regeneration. Permeability measurements after photocatalytic treatment confirmed effective flux recovery, supporting the operational durability of the developed membranes.

The increasing occurrence of persistent and bio-recalcitrant organic pollutants in aquatic environments necessitates the development of more resilient and efficient water treatment technologies. Conventional treatment processes often fail to remove such stable contaminants, prompting growing interest in integrated advanced systems. Photocatalytic membranes represent a promising solution due to the synergistic combination of separation and catalytic degradation. In this study, ZnO thin films were deposited by spin coating onto smectite–zeolite ceramic membranes (MS10/Z90), with one to three layers applied to control catalyst thickness (M1–M3). SEM analysis showed that increasing the number of layers led to a thicker, more homogeneous ZnO coating, while XRD confirmed enhanced crystallinity and larger crystallite size. Water permeability decreased from 623 L.h-1.m-2.bar-1 for the uncoated MS10/Z90 membrane to 506, 439, and 350 L.h-1.m-2.bar-1 respectively for M1, M2, and M3 after coating. Photocatalytic performance was assessed using Rhodamine B (RhB) as a model dye, achieving degradation efficiencies of 83.0%, 94.6%, and 99.1% for M1, M2, and M3, respectively, following pseudo-first-order kinetics. The free radical scavenging assays confirmed that hydroxyl radicals (•OH) were responsible for the RhB conversion.These results highlight the key influence of ZnO layer thickness and mass transfer on photocatalytic performance, de-monstrating the multifunctionality of ZnO-coated membranes, including efficient pollu-tant degradation and self-cleaning capability.

Metformin, a widely prescribed antidiabetic drug, is a representative small (≈0.5–0.6 nm), hydrophilic (log P ≈ −1.43), and positively charged (pKₐ ≈ 12.4) emerging contaminant. Because its molecular size is well below the pore size of ultrafiltration membranes (>2 nm), it cannot be efficiently removed by size exclusion alone, and its high solubility and poor biodegradability further complicate conventional treatment. In this context, hybrid ceramic membranes incorporating adsorptive functionalities offer a promising alternative. However, the fouling behavior of such hybrid systems remains quantitatively uncharacterized. This study provides a quantitative assessment of flux decline and fouling reversibility in kaolin-based membranes containing 0, 5, and 10 wt.% activated carbon, evaluated for metformin removal under dead-end filtration at 4 bars, using a synthetic feed concentration of 20 mg L⁻¹ at neutral pH (≈6.8) over 60 min. Increasing AC content raises open porosity from 29.1% (M0%) to 34.2% (M5%) and 39.1% (M10%), and water permeability from 3.3 to 10.9 and 28.4 L m⁻² h⁻¹ bar⁻¹, respectively, without significantly compromising mechanical integrity (>20 MPa). The porosity enhancement is accompanied by a systematic improvement in apparent metformin removal, consistent with a contribution from carbon- and phosphorus-containing phases detected after thermal treatment (which provides abundant surface functional groups for electrostatic and π–π interactions) and is consistent with the observed improvement in permeability and apparent metformin removal. Consequently, metformin apparent removal after 60 min increases from 56.1% (M0%) to 76.2% (M5%) and 91.1% (M10%), while total fouling decreases from 38.5% to 20.5% and 11.0%, and irreversible fouling from 23.1% to 13.6% and 6.0%, respectively.