Printing ink wastewater treatment using combined hydrodynamic cavitation and pH fixation.

Printing ink wastewater (PIW) carries a heavy load of pollutants, the composition of which makes treatment difficult, especially when trying to minimize the pollution load. According to the latter, the present study aims to investigate PIW treatment with different various methods and to determine the maximum color, COD (chemical oxygen demand) and TSS (total suspended solids) removal. First, hydrodynamic cavitation (HC) was tested and the effect of hydrogen peroxide dosage (0-10 g L-1), and pH (3, 5, 8, 10) was examined concerning the removal of PIW initial COD concentrations 4000 and 8000 mg L-1. Removal was high (more than 81%) only at pH 5 in HC reactor. The second method involved treatment with separate pH fixation of the undiluted PIW (COD 17000 mg L-1, actual pH 8 ± 0.2). This treatment, maximized removals, reaching reduction of the initial values more than 91%, at pH 5. Finally, PIW was treated with a combination of the above methods, leading to 93-97% removals for 8000 mg L-1 PIW treatment and 97-99% for 17000 mg L-1 PIW respectively. Process cost calculations showed that the latter method is an effective and affordable treatment method for PIW streams, while toxicity tests of the treated PIW showed substantial toxicity reduction.

Treatment of printing ink wastewater using a continuous flow electrocoagulation reactor.

Printing ink wastewater from printing facilities is difficult to treat because of its heavy pollutant load (chemical oxygen demand - COD, color and total suspended solids - TSS). In this study undiluted printing ink wastewater with high COD (i.e., 20,000 mgL-1) was treated using a highly efficient, continuous flow electrocoagulation reactor with aluminum electrodes. The parameters investigated were: initial COD concentration (4000, 10,000 and 20,000 mgL-1), current density (21, 42 and 83 mAcm-2), and inlet flow rate (6, 8 and 10 mLmin-1). All parameters showed great efficiency in terms of pollutant removal for diluted printing ink wastewater. For undiluted printing ink wastewater treatment, COD, color, and TSS removal were maximized at 6 mLmin-1 flow rate reaching 82%, 98%, and 85% COD, color, and TSS removal, respectively, by applying the lower tested current density 21 mAcm-2. COD, color and TSS removal increased with increasing current density. For undiluted printing ink wastewater and a flow rate of 8 mLmin-1, COD removal was between 42 and 88%, color reduction between 85 and 99%, and TSS reduction between 83 and 98% when the applied current was increased (from 21 to 83 mAcm-2). Lower pollutant removal was observed at the highest flow rate of 10 mLmin-1 for all current densities tested. Process cost calculations in terms of electrical energy, electrode material consumption and sludge disposal, showed that the use of continuous flow electrocoagulation reactor (with flow rate 6 mLmin-1, and at 21 mAcm-2) is an affordable and effective treatment method for printing ink wastewater streams with very high COD. Sludge characterization showed Al-silicate-rich sludge. Particle sizes increased after treatment and Cu and Ti were detected in the sludge. A post-treatment stage is necessary before discharging effluent into water bodies.

Pilot-scale hybrid system combining hydrodynamic cavitation and sedimentation for the decolorization of industrial inks and printing ink wastewater.

A pilot-scale hydrodynamic cavitation (HC) system followed by sedimentation (SED) was used for the decolorization of 5 industrial-grade inks, a fluid containing a mixture of the five industrial grade inks (MIX) and printing ink wastewater (PIW). The pilot scale HC reactor combines a Venturi tube with a 31 holes orifice plate accommodated in the vena-contracta of Venturi. The study aimed to define optimal operating conditions, i.e., hydrogen peroxide concentration (H2O2), pH and combined HC/SED treatment time, to achieve decolorization and reduce HC operation time. Under the optimal conditions at the proposed HC/SED system, color removal reached 92%, 91%, 90%,98% and 90%, for black, red, yellow, cyan, and green ink respectively (at pH 8 without H2O2 addition). In the same system, color removal for PIW was 92%, whereas for MIX decolorization reached more than 90% for all the wavelengths in the selected spectrum 300-700 nm at HC/SED system (at pH 8 and 1 g L-1 hydrogen peroxide). The suspended particles were characterized by measurements of the particle size distribution and of the respective zeta potential. The equivalent cavitation yields, electric energy consumption and operating costs were calculated. The present work's results suggested that HC combined with sedimentation has a great potential for real applications and is superior compared to other technologies (i.e., H2O2 alone, sedimentation alone or even HC with or without H2O).

Printing Ink Wastewater Treatment Using Hydrodynamic Cavitation and Coagulants/Flocculants.

Raw printing ink wastewater (PIW) was treated with various inorganic coagulants and organic flocculants (anionic and cationic polyacrylamides). These processes were also examined as post treatment step following hydrodynamic cavitation. Treatment effectiveness was assessed through color, chemical oxygen demand (COD) and total suspended solids (TSS) removal. The addition of 4500 mg L-1 polyaluminum chloride coagulant in undiluted PIW (COD: 17000 mg L-1) resulted in 99% color removal, 96% COD and TSS removal, after settling for 2 h. The addition of 10 mg L-1 of anionic polyacrylamides in the sample reduced settling time to only 5 min, with concomitant 96-98% removal efficiency. The addition of a 4 min hydrodynamic cavitation pretreatment step reduced coagulant addition by 33%, for the treatment of undiluted PIW (with 10 mg L-1 anionic polyacrylamide), while removals were ranged between 96 and 98%. Economic analysis for the undiluted PIW showed that costs were reduced by ca. 20% with the hydrodynamic cavitation pretreatment step. Moreover, sludge characterization showed the presence of maghemite, aluminum chloride and potassium aluminum silicate. Finally, toxicity tests revealed a significant attenuation of the toxic potential of undiluted PIW, thus indicating the enhanced efficiency of the proposed combined process (hydrodynamic cavitation and coagulation/flocculation).

Novel composites materials from functionalized polymers and silver coated titanium oxide capable for calcium phosphate induction, control of orthopedic biofilm infections: an "in vitro" study.

Three copolymers containing the functional groups P=O, S=O and C=O were prepared, and upon the introduction in calcium phosphate aqueous solutions at physiological conditions, "in vitro" were induced the precipitation of calcium phosphate crystals. The investigation of the crystal growth process was done at constant supersaturation. It is suggested that the negative end of the above functional groups acts as the active site for nucleation of the inorganic phase. In order to obtain the copolymer further antimicrobial activity, titania (TiO(2)) nanocrystals were incorporated in the polymer matrix after silver coverage by UV radiation. The antimicrobial resistance of the composite material (copolymer-titania/Ag) was tested against Staphylococcus epidermidis (SEM), Staphylococcus aureus (SAM), Candida parapsilosis (CAM) and Pseudomonas aeruginosa (PAM), microorganisms, using cut parts of "pi-plate" that covered with the above mentioned composite. The antimicrobial effect increased as the size of the nanocrystals TiO(2)/Ag decreased, the maximum achieved with the third polymer that contained also quartenary ammonium groups.

Membrane filtration of olive mill wastewater and exploitation of its fractions.

Olive mill wastewater (OMW) produced from small units scattered in rural areas of Southern Europe is a major source of pollution of surface and subsurface water. In the present work, a treatment scheme based on physical separation methods is presented. The investigation was carried out using a pilot-plant unit equipped with ultrafiltration, nanofiltration, and reverse osmosis membranes. Approximately 80% of the total volume of wastewater treated by the membrane units was sufficiently cleaned to meet the standards for irrigation water. The concentrated fractions collected in the treatment concentrates were characterized by high organic load and high content of phenolic compounds. The concentrates were tested in hydroponic systems to examine their toxicity towards undesired herbs. The calculations of the cost of the overall process showed that fixed and operational costs could be recovered from the exploitation of OMW byproducts as water for irrigation and/or as bioherbicides.

Effect of proteoglycans on hydroxyapatite growth in vitro: the role of hyaluronan.

The effect of cartilage proteoglycans on HA seed crystal growth was studied using a system providing constant supersaturation with respect to HA. The monomers were much less effective than the aggregates in reducing the rate of HA growth, which correlates with their affinity for the HA crystals. Hyaluronan, which is a normal constituent of the proteoglycan aggregates, behaved as a strong inhibitor of HA seed crystal growth and had an affinity constant similar to that of proteoglycan aggregates. The results indicate that inhibition of HA seed crystal growth is mediated through the interaction of hyaluronan with HA crystal surface and that the proteoglycans add to the volume of the adsorbate causing steric hindrance.

Functionalization of synthetic polymers for potential use as biomaterials: selective growth of hydroxyapatite on sulphonated polysulphone.

A novel composite made of biocompatible synthetic polymer (Sulphonated Polysulphone, SPSPH) which may be easily fabricated in various shapes and synthetic hydroxyapatite (HAP) was prepared. The preparation was done by the spontaneous precipitation of HAP in aqueous suspensions of the polymer particles. The time the precipitation process was allowed to proceed was used to regulate the inorganic content of the composite. The preparation thus obtained, in addition to its effectiveness in inducing HAP formation, could be easily fabricated in various shapes, including films. The SPSPH-HAP composite films, surface area totaling ca. 30 cm2 induced the exclusive formation of HAP with rates proportional to the solution supersaturation. No induction times preceded the formation of HAP. Kinetics analysis with respect to HAP yielded an apparent order of precipitation of 6.0+/-0.4, suggesting polynuclear growth with the formation of nuclei above nuclei. The surface energy calculated from the rates of crystal growth on the polymeric substrate gave for HAP the value of 185 mJ m(-2) of order of magnitude typical for crystalline solids.

Effect of surface roughness of hydroxyapatite on human bone marrow cell adhesion, proliferation, differentiation and detachment strength.

Initial attachment of osteoblast cells and mineralization phenomena are generally enhanced on rough, sandblasted substrata. In the present work the effect of surface roughness of hydroxyapatite (HA) on human bone marrow cell response was investigated. Human bone marrow cells were plated onto HA disc-shaped pellets, prepared from synthetic HA powder. The pellets were sintered and polished with SiC paper 180-, 600- and 1200-grit, resulting in three surface roughness grades. Cell adhesion, proliferation and differentiation (evaluated with the expression of ALP activity) were determined following various incubation periods. Cell detachment strength was determined as the shear stress required to detach a given quantity of the adherent cells from the different substrata, using a rotating disc device that applied a linear range of shear stresses to the cells. The cells attached and grew faster on culture plastic in comparison with HA. No statistically significant differences were observed in the expression of ALP activity on all three HA surfaces and culture plastic. Cell adhesion, proliferation and detachment strength were surface roughness sensitive and increased as the roughness of HA increased. The percentage of the adherent cells decreased in a sigmoidal mode as a function of the applied shear stress. In conclusion, surface roughness of HA generally improved the short- and longer-term response of bone marrow cells in vitro. This behavior could be explained by the selective adsorption of serum proteins.

The kinetics of mineralization of human dentin in vitro.

The prospect of restoration of damaged dental tissues has recently attracted great interest. An understanding of the remineralization of human dentin in vitro was attempted by using super-saturated calcium phosphate solutions at sustained supersaturation by means of a constant solution composition method. The direct growth of HAP from solutions of low supersaturation on powdered whole human dentin was confirmed. Moreover, it was found that the kinetics were similar to those of the seeded growth at synthetic HAP. A high apparent activation energy pointed to a surface-controlled mechanism.

The mineralization of enamel surfaces. A constant composition kinetics study.

The in vitro remineralization of acid-etched enamel surfaces offers an attractive model for simulating carious lesion recalcification and the repair of teeth in the oral environment. In the present work the influence of the extent of etching with hydrochloric and phosphoric acids has been examined. The kinetics of growth of hydroxyapatite as an exclusive phase on the pretreated enamel surfaces has been studied by means of a constant solution composition procedure. This method enables studies to be made at low constant supersaturations so that the stoichiometry of the precipitating phase may be defined. The very small rates of mineralization with HAP were determined with a precision hitherto unattainable. In addition, the influence of fluoride ion in enhancing the remineralization of damaged enamel has been investigated.

The remineralization of fluoride-treated bovine enamel surfaces.

Various etching methods are examined with respect to their ability to induce the surface nucleation and growth of fluorapatite from solutions of low, sustained supersaturation with respect to hydroxyapatite and fluorapatite. The constant composition kinetics method enables the rates of remineralization to be precisely determined, and the possibility of the direct growth of fluorapatite on calcium fluoride crystals in calcium phosphate solutions of low supersaturation has also been examined.

Assessment of encrustations on polyurethane ureteral stents.

PURPOSE: To determine the composition and the extent of crystalline (and other) encrustation on ureteral catheters inserted under sterile conditions in stone formers, in comparison with catheters of the same type inserted in nonstone formers for the same time but for different clinical reasons. MATERIALS AND METHODS: Forty consecutive self-retained polyurethane pigtail ureteral catheters removed by cystoscopy between November 2000 and February 2002 were studied, 30 from stone formers and 10 from patients without stone histories. The mean dwelling time was 55 days for the stone formers and 79 days for the other patients. The encrustations were collected and analyzed with Fourier-transform infrared spectroscopy, powder X-ray diffraction, or both. The stones from nine of the patients were also subjected to the same spectroscopic analysis. Representative sections of the catheters were investigated by scanning electron microscopy and energy-dispersive X-ray analysis. RESULTS: The most common encrustation in stone formers was calcium oxalate monohydrate. In patients without stones, deposits of organic compounds were found consistently. The mean mass of encrustation of stone formers was larger (71.05 mg) than that of patients without stones (1 mg). CONCLUSIONS: Calcium oxalate is the predominant type of encrustation on ureteral catheters in stone formers. Prevention of heavy encrustation should be directed to therapeutic measures concerning calcium oxalate lithiasis and development of new materials by the medical industry that are less prone to encrustation.

Screening biomaterials with a new in vitro method for potential calcification: porcine aortic valves and bovine pericardium.

Calcification is still a major cause of failure of implantable biomaterials. A fast and reliable in vitro model could contribute to the study of its mechanisms and to testing different anticalcification techniques. In this work, we attempted to investigate the potential calcification of biomaterials using an in vitro model. We purposed to test the ability of this model to screening possible anticalcification efficacy of different biomaterials. Porcine heart valve (PAV) and bovine pericardial (BP) tissues, fixed with glutaraldehyde were immersed into biological mimicking solution, where the pH and the initial concentrations of calcium and phosphoric ions were kept stable by the addition of precipitated ions during calcification. Kinetics of calcification was continuously monitored. The evaluation of biomaterials was carried out by comparing the kinetic rates of formation of calcific deposits. After 24 h, the calcific deposits on PAVs were found to be developed at significant higher rates (ranged from 0.81 x 10(-4)-2.18 x 10(-4)mol/min m2) than on BP (0.19 x 10(-4)-0.52 x 10(-4)mol/min m2) (one-way ANOVA, p < 0.05) depending on the experimental conditions (supersaturation of the solution). Parallel tests for similar biomaterials implanted subcutaneously in animal (rat) model showed after 49 days that significant higher amounts of total minerals deposited on PAV (236.73+/-139.12, 9 animals mg minerals/g dry net tissue) (mean+/-standard deviation) compared with that formed on BP (104.36+/-79.21, #9 mg minerals/g dry net tissue) (ANOVA, p < 0.05). There is evidence that in vitro calcification was correlated well with that of animal model and clinical data.

Epitaxial considerations in urinary stone formation. II. The oxalate-phosphate system.

We examined epitactic relationships between hydroxyapatite (HAP) and the hydrates of calcium oxalate from a crystallographic point of view. We also examined the growth of HAP on the calcium oxalate surfaces at a constant supersaturation, we maintained by the controlled addition of solutions containing the lattice ions of the precipitating phase. Calcium oxalate trihydrate was the only salt that induced HAP overgrowth. The latter phase, however, was found to be a suitable substrate for the growth of calcium oxalate monohydrate.

Model experimental system for investigation of heart valve calcification in vitro.

A model system was developed for the in vitro quantitative investigation of the calcification process occurring in heart valves. The process of heart valve calcification consists of the formation of calcium phosphates at the heart valve-biological fluid interface. Calcium phosphate deposits may consist of more than one calcium phosphate mineral phase, differing with respect to their physical and chemical properties. The kinetics of the formation of hydroxyapatite, the model inorganic compound for the calcified deposits, was precisely monitored in a reactor containing supersaturated calcium phosphate solutions in which the heart valves were immersed after being treated with glutaraldehyde and mounted on special racks. The precipitation process, accompanied with proton release in the solution, was monitored by a pair of glass-saturated calomel electrodes. Upon initiation of the formation of calcium phosphate deposits, the supersaturation in the working solution was reestablished through the addition of titrant solutions made with the appropriate concentration to compensate for the ions precipitated. With this methodology, not only the rates were measured very precisely but also the nucleation capability of the various substrates could be evaluated. Moreover, it was possible to identify the formation of intermediate calcium phosphate phases formed during the calcification process. Valves previously treated with glutaraldehyde were shown to nucleate octacalcium phosphate, which at lower supersaturations converted to the thermodynamically more stable hydroxyapatite. The rates measured were found to depend on the solution supersaturation, while the apparent order of the precipitation process was found to be 1.

Physicochemical and microscopical study of calcific deposits from natural and bioprosthetic heart valves. Comparison and implications for mineralization mechanism.

Natural and bioprosthetic heart valves suffer from calcification, despite their differences in etiology and tissue material. The mechanism of developing calcific deposits in valve tissue is still not elucidated. The calcific deposits developed on human natural and bioprosthetic heart valves have been investigated and compared by physicochemical studies and microscopy investigations and the results were correlated with possible mechanisms of mineral crystal growth. Deposits from 16 surgically excised calcified valves (seven natural aortic and nine bioprosthetic porcine aortic valves) were examined by chemical analysis, FTIR, XRD, and SEM-EDS. The Ca/P molar ratio of the deposits from bioprosthetic valves (1.52+/-0.06) was significantly lower compared to that of the natural valves (1.83+/-0.03) (p=0.05, 1-way ANOVA). SEM-EDS examination of the two types of valve deposits revealed the coexistence of large (>20 microm) and medium (5-20 microm) plate-like crystals as well as microcrystalline (<5 microm) calcium phosphate mineral formations. The results confirmed the hypothesis that the mineral salt of calcified valves is a mixture of calcium phosphate phases such as dicalcium phosphate dihydrate (DCPD), octacalcium phosphate (OCP) and hydroxyapatite (HAP). DCPD and OCP are suggested to be precursor phases transformed to HAP by hydrolysis. The lower value of the Ca/P molar ratio found in the bioprostheses, in comparison with that corresponding in natural valves, was ascribed to the higher content in these deposits in precursor phases DCPD and OCP which were subsequently transformed into HAP. On the basis of chemical composition of the deposits and their morphology it is suggested that crystal growth proceeds in both types of valves by the same mechanism (hydrolysis of precursor phases to HAP) in spite of their differences in etiology, material, and possible initiation pathways.

Epitaxial considerations in urinary stone formation. I. The urate-oxalate-phosphate system.

We examined the epitaxial relationships and the growth kinetics of hydroxyapatite and calcium oxalate monohydrate on uric acid and sodium urate at sustained supersaturations of hydroxyapatite and calcium oxalate monohydrate, respectively. These phases can grow even at very low supersaturations on both uric acid and sodium urate seed crystals. Our findings agree with theoretical predictions for epitaxial growth. The crystallization kinetics of both hydroxyapatite and calcium oxalate monohydrate are identical with those for the growth of seed crystals of these phases in pure supersaturated solutions.

A model system for the investigation of urinary stone formation.

OBJECTIVE: To develop an in vitro model system for the investigation of calcium oxalate urinary stones under conditions of spontaneous precipitation. MATERIALS AND METHODS: Using a calcium-ion selective electrode and automatic titrator, a test solution was kept supersaturated with calcium oxalate and the rate of crystallization measured. RESULTS: During the spontaneous precipitation at constant supersaturation at 37 degrees C, the induction times required for the precipitation of calcium oxalate monohydrate were inversely proportional to the supersaturation of the solution. No transient phases were identified and the interfacial energy determined from kinetic analysis was 28.4 mJ/m2. The rates of precipitation showed a first-order dependence on the degree of supersaturation and were in good agreement with those reported for the in vivo formation of calcium oxalate monohydrate stones. CONCLUSION: This experimental model system allows precise measurements of the kinetics of calcium oxalate monohydrate. From the dependence of the rates of precipitation on supersaturation, a mechanism controlled by surface diffusion is suggested.

Encrustation of a metal alloy urinary stent: a mechanistic investigation.

MATERIALS AND METHODS: A section of a metal stent consisting mainly of tantalum coated partially by strongly adhering calcium oxalate monohydrate (COM) crystals was immersed in supersaturated solutions prepared from calcium chloride and sodium oxalate at 37 degrees C and ionic strength 0.15 M in NaCl. Abstract OBJECTIVES: To investigate the kinetics of encrustation of a metall alloy urinary stent system in vitro by calcium oxalate and characterize the crystals forming from solutions supersaturated with respect to all calcium oxalate hydrates. RESULTS: The COM-coated stent mineralized upon immersion in the supersaturated solutions. The process was monitored with a calcium ion-selective electrode and the rates were measured at conditions of sustained solution supersaturation. COM crystals formed on the stent and the rate of COM crystal growth yielded a second-order dependence on the solution supersaturation. CONCLUSIONS: The deposition of COM crystals on the metal stents coated partially with COM crystals by adhesive forces was found to be most important for the acceleration of the encrustation process. The dependence of the rates on the solution supersaturation suggested absence of secondary nucleation and a surface-controlled process for the encrustation process.