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Clean Technologies

Clean Technologies is an international, peer-reviewed, open access journal of scientific research on technology development aiming to reduce the environmental impact of human activities, published bimonthly online by MDPI.

Quartile Ranking JCR - Q2 (Environmental Sciences | Engineering, Environmental)

All Articles (474)

Anthropogenic CO2 emissions have accelerated climate change, prompting the need for effective capture technologies. Adsorption using clay-based sorbents offers an eco-friendly alternative, although performance often requires enhancement. This study explored mechanochemical modification of two halloysite-rich kaolin clay samples—iron-poor (Hal) and iron-rich (HalFe)—using locust bean gum and quillaja saponin and compared their CO2 uptake with the calcined counterparts (CHal, CHalFe). All samples were characterized using standard techniques, and their CO2 uptake was measured volumetrically across 0.1–20 bar and 15–35 °C. Modified sorbents showed enhanced mesoporosity and binding sites, increasing CO2 uptake by up to 26% at 20 bar (11.85 mg/g) and 125% at 1 bar (2.25 mg/g). Calcination, however, reduced surface area and sorption capacity. Isosteric heat values remained within the physisorption range, as supported by FTIR, XRF, and XPS, which showed no bulk carbonate formation. These sorbents show lower CO2 uptakes than conventional ones. Yet their low costs, abundance, biocompatibility, and solvent-free synthesis indicate strong potential for large-scale applications, especially for low-pressure implementations such as landfills. Further detailed studies on kinetics, thermodynamics, and sorbent regeneration are needed. Spent sorbents can potentially be repurposed for subsequent use in other applications, e.g., water treatment, construction materials, thereby minimizing waste production and supporting circular economy principles.

3 February 2026

SEM images of raw and LBG/SPN modified Hal and HalFe samples.

Scale-Up and Application of a Green Detergent Under Industrial Conditions to Remove Petroleum Derivatives: Comparison with Commercial Degreasers

  • Rita de Cássia Freire Soares da Silva,
  • Thaís Cavalcante de Souza and
  • Leonie Asfora Sarubbo
  • + 5 authors

The widespread use of petroleum derivatives in industrial settings poses a challenge due to their toxicity and the difficulty of removing them from tanks, pipes, and equipment. Conventional degreasers are generally expensive, toxic, and harmful to workers’ health and the environment. In this study, an environmentally friendly biodetergent formulated from natural ingredients was produced in a pilot plant with 480 L h−1 capacity, in 250 L homogenizers, at 3500 rpm and 80 °C, and its performance evaluated under different operating conditions. Furthermore, the biodetergent efficiency was compared with that of commercial degreasers commonly used in industrial settings. Stability tests indicated 100% stable emulsion with 2.0% fatty alcohol and 1.0% stabilizing gum after one week of storage. In application tests, the biodetergent promoted up to 100% removal of heavy fuel oil (OCB1) and diesel from metal surfaces, both in concentrated and (1:1 v/v) diluted forms. In direct comparisons, the product performed equally or better than commercial degreasers, notably removing >95% of OCB1 in 10 min and maintaining efficiency after multiple reuse cycles. Unlike acidic or solvent-based formulations, the biodetergent did not induce corrosion on pieces or release toxic vapors when applied to heated surfaces. In summary, the developed bioproduct demonstrated industrial scalability and high efficiency, constituting a sustainable alternative for petrochemical cleaning operations in onshore and offshore environments.

3 February 2026

Homogenizing tank, with a capacity of 250 L, belonging to the biodetergent production pilot plant of the Advanced Institute of Technology and Innovation (IATI).

Per- and polyfluoroalkyl substances (PFASs) are persistent and mobile contaminants of global concern, and, while granular activated carbon (GAC) is widely used for their removal, it is limited by the high regeneration and disposal costs. This study investigates surface-modified clinoptilolite zeolites as low-cost and thermally regenerable alternatives to GAC for PFAS removal from water. Natural clinoptilolite was modified through acid washing, ion exchange with Fe3+ or La3+, grafting with aminosilane (APTES) or hydrophobic silane (DTMS), dual APTES + DTMS grafting, and graphene oxide coating. The adsorption performance was evaluated for perfluorooctanoic acid (PFOA, C8) and perfluorobutanoic acid (PFBA, C4) at 100 µg L−1 in single- and mixed-solute systems, with an additional high-concentration PFOA test (1 mg L−1). PFAS concentrations were quantified by liquid chromatography–tandem mass spectrometry (LC–MS/MS) using a SCIEX 7500 QTRAP system coupled to a Waters ACQUITY UPLC I-Class. Raw zeolite showed limited PFOA removal (4%), whereas dual-functionalized APTES + DTMS zeolites achieved up to 93% removal, comparable to GAC (97%) and superior to single-silane or metal-exchanged variants. At lower concentrations, modified zeolites effectively removed PFOA but showed limited PFBA removal (<25%), highlighting ongoing challenges for short-chain PFASs. Overall, the results demonstrate that dual-functionalized clinoptilolite zeolites represent a promising and scalable platform for PFAS remediation, particularly for mid- to long-chain compounds, provided that strategies for enhancing short-chain PFAS binding are further developed.

3 February 2026

PFAS sources, exposure pathways, and human health risks.

Meat-processing wastewater (MPWW) is rich in nutrients and organic matter. This study assessed its potential as feedstock for microalgal biomass production while enabling wastewater treatment. In batch assays, the microalgae-based consortium grew in raw MPWW, and its synergy with the native wastewater microbial community enhanced the chemical oxygen demand (COD) removal rate. If suspended solids were pre-removed from wastewater, COD removing rates improved from 828.5 ± 60.5 to 1097.5 ± 22.2 mg L−1 d−1. In a raceway system operated in fed-batch mode with sieved and sedimented MPWW, COD removal was consistently achieved across feeding cycles, despite the variability in wastewater composition, reaching rates of up to 806.3 ± 0.0 mg L−1 d−1. Total nitrogen also decreased in most cycles. Microalgal biomass, estimated from total photosynthetic pigment’s concentration, increased from 0.4 to 17.9 µg mL−1. The microalgae-based consortium became more diverse over time, harboring at the end, additional eukaryotic taxa such as protozoan grazers and fungi (e.g., Heterolobosea class and Trichosporonaceae and Dipodascaceae families), although their roles in removal processes remain unknown. This study highlights the potential use of real MPWW as feedstock for microalgal-based biomass production with concomitant carbon/nutrient load reduction, aligning its implementation with circular economy percepts.

3 February 2026

Scheme illustrating the prototype raceway system used in the experiment: (a) axonometric view, and (b) top view of the raceway system. White arrows represent the flow direction.

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Clean Technol. - ISSN 2571-8797