46 documents found, page 1 of 5
Comparison of a variety of physico-chemical techniques in the chronological cha...
Silva, Ana Catarina; Rocha, P.; Antelo, J.; Valderrama, P.; Lopez, R.; Geraldo, Dulce; Proenca, M. F.; Pinheiro, J. P.; Fiol, S.; Bento, M. FátimaThe degree of stability and maturity of the organic matter are fundamental features of the chemical characterization of compost. These characteristics are related to the extensive formation of aromatic structures and of oxygen-containing functional groups. The increase of the amount of these chemical moieties can be assessed by different analytical methodologies, based on thermal, spectrophotometric, and electr...
Comparison of cadmium binding by humic and fulvic acids extracted from compost ...
Rocha, P.; Silva, Ana Catarina; Antelo, J.; Bento, M. Fátima; Bettencourt, Ana Paula; Fiol, S.; Geraldo, Dulce; López, R.; Macías, F.; Pinheiro, J. P.Compost is a bio-sustainable material produced by the controlled decomposition of the organic wastes. Composting can be employed for the urban organic waste treatment in alternative to incineration or landfill disposal [1]. The properties of compost are closely related to the presence of humic-like substances (HS). Both fulvic acids (FA) and humic acids (HA) contain a significant amount of carboxylic acids and ...
Comparison of cadmium binding by humic and fulvic acids extracted from two comp...
Silva, Ana Catarina; Rocha, P.; Antelo, J.; Bento, M. Fátima; Bettencourt, Ana Paula; Fiol, S.; Geraldo, Dulce; López, F.; Macías, F.; Pinheiro, J. P.Composting has been proven to be an environmentally friendly process for urban organic waste, that can represent an opportunity for new uses under the circular economy framework. The binding of cadmium to fulvic-like and humic-like acids extracted from compost of algae and urban residues were evaluated, and the results show significant differences. The fulvic and humic acids from algae compost bind cadmium more...
Characterization of organic matter at different stages of a composting process
Silva, Ana Catarina; Rocha, P.; Antelo, J.; Bento, M. Fátima; Bettencourt, Ana Paula; Ferreira, Paula M. T.; Fiol, S.; Geraldo, Dulce; López, R.The characterization of the organic matter from raw organic wastes, unmatured compost and maturated compost was performed by different techniques: gravimetric, FTIR-ATR, TGA and from the ability of their extracts to bind Cd2+ (evaluating the free cadmium ion by AGNES). Although the amount of humic-like and fulvic-like acids did not change significantly, the structure and properties of the organic matter changed...
Effect of monomer organization on the behavior of PSS-PS micelles
Alves, Nuno G.; Rocha, Luciana S.; Moreira, José; Costa, Ana M. Rosa da; Pinheiro, J. P.Six copolymers of styrenesulfonate-styrene (SS-S) of varying molecular weights were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization and proven to give rise to micelles in aqueous solution. Three are diblock copolymers (PSS-b-PS), while the other three have a random distribution of the two monomers, probably forming a gradient (PSS-co-PS). The latter ones form micelles of small...
Ligand size polydispersity effect on SSCP signal interpretation
Rocha, Luciana S.; Botero, Wander G.; Alves, Nuno G.; Moreira, José; Costa, Ana M. Rosa da; Pinheiro, J. P.The present study aims to establish unambiguously the conditions required for the validity of the average diffusion (D) approximation in fully labile systems with significant ligand size polydispersity. The average diffusion coefficient is a key parameter in mass transfer that affects signal interpretation in dynamic electroanalytical techniques. To achieve this goal, the binding of Cd(II) and Pb(II) to binary ...
Stability of core/shell quantum dots-role of pH and small organic ligands
Domingos, R. F.; Franco, C.; Pinheiro, J. P.The improvement of knowledge about the toxicity and even processability, and stability of quantum dots (QD) requires the understanding of the relationship between the QD binding head group, surface structure, and interligand interaction. The scanned stripping chronopotentiometry and absence of gradients and Nernstian equilibrium stripping techniques were used to determine the concentration of Cd dissolved from ...
Interactions of core-shell quantum dots with metal resistant bacterium Cupriavi...
Slaveykova, V. I.; Pinheiro, J. P.; Floriani, M.; Garcia, M.In the present study we address the interactions of carboxyl-CdSe/ZnS core/shell quantum dots (QDs),as a model of water dispersible engineered nanoparticles, and metal resistant bacteria Cupriavidusmetallidurans, largely used in metal decontamination. The results demonstrate that QDs with averagehydrodynamic size of 12.9 nm adhere to C. metallidurans. The percentage of bacterial cells displayingQD-fluorescence ...
Electrochemical methods for speciation of trace elements in marine waters. Dyna...
Mota, A. M.; Pinheiro, J. P.; Simões Gonçalves, M. L.The contribution of electrochemical methods to the knowledge of dynamic speciation of toxic trace elements in marine waters is critically reviewed. Due to the importance of dynamic considerations in the interpretation of the electrochemical signal, the principles and recent developments of kinetic features in the interconversion of metal complex species will be presented. As dynamic electrochemical methods, onl...
Preparation and characterization of low dispersity anionic multiresponsive core...
Pinheiro, J. P.; Moura, L.; Fokkink, R.; Farinha, J. P. S.We prepared anionic multistimuli responsive core–shell polymer nanoparticles with very low size dispersity. By using either acrylic acid (AA) or methacrylic acid (MA) as a comonomer in the poly(N-isopropyl acrylamide) (PNIPAM) shell, we are able to change the distribution of negative charges in the nanoparticle shell. The particle size, volume phase transition temperature, and aggregation state can be modulated...