Lincoln L. Romualdo

Performance and kinetic-mechanistic aspects in the electrochemical degradation of sulfadiazine on boron-doped diamond electrode

The electrochemical performance of boron-doped diamond (BDD) electrode in the electrochemical degradation of wastewaters containing sulfadiazine (SDZ) using a filter-press reactor is presented and discussed. The electrooxidation of the SDZ (volume of 0.5 L, with a SDZ initial concentration of 250 mg L-1) obtained at optimized conditions (current density of 36 mA cm-2, pH 7.0 and volume flow rate of 5.0 L min-1) showed that at the end of only 2 h of electrolysis (corresponding to a charge passed through the cell per unit volume of the wastewater of 5.2 Ah L-1) SDZ was totally eliminated. The reduction of the wastewater organic load, monitored by its chemical oxygen demand (COD) showed that the antibiotic was virtually all mineralized. Under optimized conditions the intermediate compounds were properly identified by gas chromatography-mass spectrometry (GC-MS) and a SDZ oxidation pathway was elucidated. Clearly the BDD electrode proved to be quite efficient for both degradation and mineralization of SDZ.

Pseudohalides of Main Group Metals: The Alcaline Earth Tricyanomethanides - The Crystal Structures of Calcium and Barium Tricyanomethanide.

The alcaline earth tricyanomethanides Mg(tcm)2-2H20, Ca(tcm)2, Sr ( tcm) 2 H 2 0 and Ba(tcm)2-2H20 were prepared from aqueous solutions of the respective chlorides and solid silver tricyanomethanide. Their infrared spectra and thermal behavior are described. The crystal structures of Ca(tcm)2 and Ba(tcm)2-2H20 were determined by single-crystal X-ray diffraction. The crystal structure of Ca(tcm)2 is identical with that found for several transition metal tricyanomethanides / l / , containing two independent interpenetrating networks. Ba(tcm)2-2H20 has a unique crystal structure corresponding to a co-ordination polymer with ninefold co-ordinated Ba atoms connected by water molecules and tricyanomethanide anions.

Preparation, Characterization and Crystal Structure of Lead(II) Tricyanomethanide

The so far unknown lead tricyanomethanide, Pb[C(CN)3]2, was obtained from a saturated aqueous solution of PbCl2 and solid AgC(CN)3. Its IR spectrum and thermal behaviour are described. The crystal structure was determined by single-crystal X-ray diffraction (trigonal, P31m, Z = 3, a = 1414.4(5), c = 409.02(6) pm, R1 = 0.0249, wR2 = 0.0527). Two crystallographically independent ninefold coordinated Pb atoms are connected by planar tricyanomethanide ions in two distinct bridging coordination modes. The Pb−N distances range between 254 and 293 pm.

Combined use of coagulation (M. oleifera) and electrochemical techniques in the treatment of industrial paint wastewater for reuse and/or disposal

In this work, water-based paint (WBP) wastewater was treated using a natural coagulant, Moringa oleifera aqueous extract (MOAE), fortified with Ca2+ (from nitrate and chloride salts). In order to improve the quality of the treated wastewater and render it suitable for disposal, an electrolytic flow process was associated with the wastewater treatment using a filter-press reactor with a boron doped diamond (BDD) electrode. The feasibility of the treatment was evidenced by the reuse of the treated wastewater in the production of a new paint (manufactured by the company supplying the raw wastewater), whose quality was compatible with the water used by the manufacturer. The best conditions for the coagulation-flocculation process involved the use of 80 mL of MOAE (50 g/L of MO and 0.125 mol/L of Ca2+) for every 1.0 L of wastewater at pH 6.5. The limiting current density (35 mA/cm2) and an electrolysis time of 90 min (charge passed of 3.68 A h/L) were used in the electrochemical treatment. Biotoxicity assays using the brine shrimp Artemia salina revealed that the mortality (in %) of microcrustaceans was reduced from 100% (raw wastewater) to only 11% at the end of the electrolysis process, in addition to eliminating the strong odor and 85% of the organic load. Moreover, microbiological tests showed that the number of mesophiles decreased by more than six orders of magnitude and there was no growth of thermotolerant coliforms (TC).

Crystal Structures and Thermal Behavior of Alkaline Earth Tricyanomethanides

The alkaline earth tricyanomethanides Mg(tcm)2 · 2H2O, Ca(tcm)2, Sr(tcm)2 ・H2O and Ba(tcm)2 · 2H2O were prepared from aqueous solutions of the respective chlorides and silver tricyanomethanide. Their IR spectra and thermal behavior are described. The crystal structures of Ca(tcm)2 and Ba(tcm)2 · 2H2O were determined by single crystal X-ray diffraction. The structure of Ca(tcm)2 is of the type found for several transition metal tricyanomethanides [1], containing two independent interpenetrating networks. Ba(tcm)2 · 2H2O has a unique crystal structure corresponding to a three-dimensional coordination polymer with nine fold coordinated Ba atoms connected by water molecules and tricyanomethanide anions.