José A. Ribeiro

Abstract Hydroponics is an advanced agricultural technique that involves growing plants without soil. Instead, plants are cultivated in a nutrient-rich water solution that provides all the essential minerals they need to thrive, allowing plants to grow either with their roots directly in the solution or supported by inert substrates like pine bark, coconut husk fiber, and rice husk. The solid waste generated from hydroponic cultivation is valuable due to its low cost, abundance, biodegradability, and renewability. These residues are rich in lignocellulosic materials, which can be extracted and refined to produce cellulose and nanocellulose (NC). In this work, cellulose and nanocellulose were extracted from residues of coconut husk fiber and a mixture of pine bark and coconut husk fiber, used in tomato and strawberry hydroponics, respectively. The residues were ground, washed, and chemically treated to obtain cellulose and NC. The chemical process involved several stages: (i) acid treatment, alkaline treatment, and bleaching to isolate cellulose, and (ii) acid hydrolysis followed by ultrasonication to obtain NC. Both materials underwent characterization using various techniques such as TGA, DSC, XRD and FTIR-ATR, which confirmed very low levels of lignin and hemicellulose. Morphological characterization through SEM revealed the presence of micro- and nano-crystals in the cellulose and NC samples, respectively, highlighting the effectiveness of the extraction method. The high purity and quality of the extracted materials make them competitive with commercially available products, suitable for applications in healthcare, food packaging, and automotive industries, while supporting recycling and reuse principles.

Abstract Active and abandoned mining sites are significant sources of heavy metals and metalloid pollution, leading to serious environmental issues. This study assessed the environmental risks posed by potentially toxic elements (PTEs), specifically arsenic (As) and antimony (Sb), in the Technosols (mining residues) of the former Pejão coal mine complex in Northern Portugal, a site impacted by forest wildfires in October 2017 that triggered underground combustion within the waste heaps. Our methodology involved determining the “pseudo-total” concentrations of As and Sb in the collected heap samples using microwave digestion with aqua regia (ISO 12914), followed by analysis using hydride generation-atomic absorption spectroscopy (HG-AAS). The concentrations of As an Sb ranging from 31.0 to 68.6 mg kg−1 and 4.8 to 8.3 mg kg−1, respectively, were found to be above the European background values reported in project FOREGS (11.6 mg kg−1 for As and 1.04 mg kg−1 for Sb) and Portuguese Environment Agency (APA) reference values for agricultural soils (11 mg kg−1 for As and 7.5 mg kg−1 for Sb), indicating significant enrichment of these PTEs. Based on average Igeo values, As contamination overall was classified as “unpolluted to moderately polluted” while Sb contamination was classified as “moderately polluted” in the waste pile samples and “unpolluted to moderately polluted” in the downhill soil samples. However, total PTE content alone is insufficient for a comprehensive environmental risk assessment. Therefore, further studies on As and Sb fractionation and speciation were conducted using the Shiowatana sequential extraction procedure (SEP). The results showed that As and Sb levels in the more mobile fractions were not significant. This suggests that the enrichment in the burned (BCW) and unburned (UCW) coal waste areas of the mine is likely due to the stockpiling of lithic fragments, primarily coals hosting arsenian pyrites and stibnite which largely traps these elements within its crystalline structure. The observed enrichment in downhill soils (DS) is attributed to mechanical weathering, rock fragment erosion, and transport processes. Given the strong association of these elements with solid phases, the risk of leaching into surface waters and aquifers is considered low. This work underscores the importance of a holistic approach to environmental risk assessment at former mining sites, contributing to the development of sustainable remediation strategies for long-term environmental protection. © 2025 by the authors.

Abstract This paper describes the development of an optical tweezers system that operates in fully automatic mode. It features image recognition for particle tracking, allowing for the optical trapping and analysis of identified targets. The system can perform analysis of forward scattered light and Raman spectroscopy of the trapped particles, facilitating the automated analysis of a large number of samples without manual intervention. By leveraging combined analytical methods and AI for robust classification, this system contributes to the advancement of automated diagnostic tools. Preliminary results demonstrate the system's effectiveness using different kinds of standard and biofunctionalized PMMA microparticles.

Abstract Purpose Pejao Mining Complex locates in Castelo de Paiva municipality and, until its closure in 1994, was one of the most important coal mines in the Douro Coalfield. This work aims to study the presence, quantify, and evaluate the dissemination of mercury (Hg), a potentially toxic element (PTE) of major public health concern by the World Health Organization (WHO), from a waste pile affected by coal fires.Materials and methods Samples from areas affected and unaffected by the combustion and from surrounding soil were collected from Fojo waste pile region. First, the Hg pseudo-total concentration was estimated for all collected samples by soil microwave-assisted digestion with aqua regia (USEPA 3051A). Then, a sequential extraction procedure (SEP), the USEPA 3200, was applied for Hg fractionation and speciation aiming to evaluate Hg mobility and bioavailability to surrounding ecosystems.Results and discussion The results obtained showed a Hg enrichment in soil samples when compared to Portuguese and international reference values for soils. Relatively to the Hg availability and mobility, although it predominates in the semi-mobile fraction, the waste pile materials exposed to combustion showed a concerning increase of Hg levels in the mobile fraction that contains the more labile Hg species, being a major source of environmental contamination by Hg.Conclusions This study allowed to conclude that combustion of mining residues increased Hg mobility, toxicity, and bioavailability, increasing the contamination potential of the coal waste pile. The methodology applied in this work can be replicated in other abandoned mines to monitor, control, and/or mitigate the Hg environmental impact in the surrounding soils and waters.

Abstract New systems with innovative design to perform measurements combining electrochemistry and surface plasmon resonance (ESPR) are currently a need to overcome the limitations of existent market solutions and expand the research possibilities of this technology. The main goal of this work was to develop a new cell to increase ESPR practical applications in several fields. To do so, a homemade SPR cell, fabricated by 3D-printing technology, was adapted for this purpose by incorporating the conventional 3-electrodes to perform the electrochemical experiments. The developed cell was fully compatible with commercial SPR substrates. After optimization of the homemade ESPR setup to perform the combined electrochemical and SPR measurements, two main applications were explored in this work. The first was the use of ESPR technology as straightforward tool to simultaneously investigate the electrical and optical properties of conducing/nonconducting polymers electrosynthetized on the SPR platforms. The conducting polymer poly(thionine) was used in this work for proof-of- concept. The second application envisaged the use of ESPR approach for simple electrodeposition of materials with enhanced plasmonic properties for sensitivity enhancement of SPR biosensors. For validation of the concept, graphene oxide (GO) was electrochemically reduced on gold substrates aiming to evaluate the plasmonic properties of graphene-modified sensing surfaces.