Conversion of foliar residues of Sansevieria trifasciata into adsorbents: dye adsorption in continuous and discontinuous systems

The study analyzed the potential of leaf powder prepared from the residual leaves of the species Sansevieria trifasciata, as a potential adsorbent for methylene blue (MB) removal. The equilibrium was reached fast for almost all concentrations after 60 min, obtaining the maximum capacity of 139.98 mg g^-1 for 200 mg L^-1. The increase in temperature disfavored the dye adsorption, with the maximum adsorption capacity of 225.8 mg g^-1, observed for 298 K. The thermodynamic parameters confirmed that the adsorption process is spontaneous and exothermic. A direct sloping curve was established for the fixed bed, with breakthrough time (t_b), column stoichiometric capacities (q_eq), and the mass transfer zone lengths (Z_m) were 1430, 1130, and 525 min; 60.48, 187.01, and 322.65 mg g^-1; and 8.81, 11.28, and 10.71 cm, for 100, 200, and 500 mg L^-1, respectively. Furthermore, in a mixture of several dyes, the adsorbent obtained the removal of 51% of the color.

Transformation of Residual Açai Fruit (Euterpe oleracea) Seeds into Porous Adsorbent for Efficient Removal of 2,4-Dichlorophenoxyacetic Acid Herbicide from Waters

Brazil's production and consumption of açai pulp (Euterpe oleracea) occur on a large scale. Most of the fruit is formed by the pit, which generates countless tons of residual biomass. A new purpose for this biomass, making its consumption highly sustainable, was presented in this study, where activated carbon (AC) was produced with zinc chloride for later use as an adsorbent. AC carbon formed by carbon and with a yield of 28 % was satisfactorily used as an adsorbent in removing the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Removal efficiency was due to the highly porous surface (Vp = 0.467 cm³ g^-1; Dp = 1.126 nm) and good surface área (SBET = 920.56 m² g^-1). The equilibrium data fit the Sips heterogeneous and homogeneous surface model better. It was observed that the increase in temperature favored adsorption, reaching a maximum experimental capacity of 218 mg g^-1 at 328 K. The thermodynamic behavior indicated a spontaneous, favorable, and endothermic behavior. The magnitude of the enthalpy of adsorption was in agreement with the physical adsorption. Regardless of the herbicide concentration, the adsorbent displayed fast kinetics, reaching equilibrium within 120 min. The linear driving force (LDF) model provided a strong statistical match to the kinetic curves. AC with zinc chloride (ZnCl₂), created from leftover açai biomass, is a potential alternative as an adsorbent for treating effluents containing 2,4-D.

Biosorption of Neodymium (Nd) from Aqueous Solutions Using Spirulina platensis sp. Strains

Rare earth elements such as neodymium (Nd) are important elements used mainly in developing new technologies. Although they are found in low concentrations in nature, they can be obtained by extracting solid samples such as phosphogypsum. Among the techniques, adsorption has been used successfully with several adsorbent materials. In this work, two strains of Spirulina platensis (LEB-18 and LEB-52) were employed as biosorbents for efficiently removing the Nd element from the aqueous media. Biosorption tests were carried out in a batch system, and the results of the biosorption kinetics showed that for both materials, the biosorption of Nd was better described by the Avrami model. Moreover, it could be considered that 80 min would be necessary to attain the equilibrium of Nd(III) using both biosorbents. The result of the biosorption isotherms showed that for both strains, the best-fitted model was the Liu model, having a maximum biosorption capacity of 72.5 mg g−1 for LEB-18 and 48.2 mg g−1 for LEB-52 at a temperature of 298 K. Thermodynamics of adsorption showed that for both LEB-18 and LEB-52 the process was favorable (∆G° < 0) and exothermic (∆H° −23.2 for LEB-18 and ∆H° −19.9 for LEB-52). Finally, both strains were suitable to uptake Nd, and the better result of LEB-18 could be attributed to the high amount of P and S groups in this biomass. Based on the results, a mechanism of electrostatic attraction of Nd3+ and phosphate and sulfate groups of both strains of Spirulina platensis was proposed.

Adsorption kinetics and equilibrium of Ni2+, Cu2+, Co2+, and Ag+ on geopolymers derived from ashes: application to treat effluents from the E-Coat printing process

Geopolymers were obtained from ashes through an alternative geopolymerization process and applied to remove Ni²⁺, Cu²⁺, Co²⁺, and Ag⁺ from synthetic aqueous media and real effluents. The study in synthetic solutions revealed that pseudo-second-order and general order models were the best to fit the kinetic curves. To represent the equilibrium curves, Langmuir and Freundlich were the most adequate. The geopolymer derived from bottom ash (GHA) was superior to adsorb Cu⁺², Co⁺², and Ag⁺¹ than the geopolymer derived from fly ash (GFA). GHA reached adsorption capacities of 279.5, 288.2, and 462.8 mg g^-1 for Co⁺², Cu⁺², and Ag⁺¹, respectively. Otherwise, GFA was the best for Ni⁺² removal, with an efficiency of 95% in low concentrations. In treating real effluents of the E-coat printing process, both GHA and GFA were efficient, with the removal of higher than 85% for all the metals. In brief, it can be stated that GFA and GHA prepared are promising materials to remove metals from aqueous media (synthetic and real), presenting fast adsorption kinetics, high adsorption capacity, and high metal removal percentage.

Effective removal of non-steroidal anti-inflammatory drug from wastewater by adsorption process using acid-treated Fagopyrum esculentum husk

In this work, buckwheat husks (Fagopyrum esculentum) were modified by acid treatment and posteriorly employed to remove the ketoprofen in batch adsorption. The characterization results indicated that a more irregular surface with new empty spaces was generated after acid treatment. The adsorptive process was favored at acidic pH = 3. The dosage of 0.85 g L^-1 was fixed for the kinetic and isothermal tests, obtaining good removal and capacity indications. The kinetic studies were better represented by pseudo-second-order, obtaining an experimental capacity of 74.3 mg g^-1 for 200 mg L^-1 of ketoprofen. An increase in temperature negatively affected the adsorption isotherm curves, resulting in a maximum capacity of 194.1 mg g^-1. Thermodynamic results confirmed the exothermic nature of the process with physical forces acting. The adsorbent presented high efficiency in treating a synthetic effluent containing different drugs and salts, 71.2%. Therefore, adsorbent development from buckwheat husks treated with a strong acid is an excellent alternative, given the good removal results and the low cost for its preparation.

Synthesis of geopolymers from fly and bottom ashes of a thermoelectrical power plant for metallic ions adsorption

A series of geopolymers were synthesized from fly and bottom ashes of a thermoelectrical power plant located in the Brazilian southern, aiming to add value for these wastes. The geopolymers were prepared in conventional and ultrasound-assisted ways and used to uptake Ag⁺, Co²⁺, Cu²⁺, and Ni²⁺ from aqueous solutions. All materials were characterized by infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and N₂ adsorption isotherms (BET and BJH methods). The results revealed that the geopolymers obtained from the conventional method presented slightly higher values of surface area and total pore volume. However, in some cases, the adsorption potential was better for the ultrasound synthesized materials. The geopolymers prepared from both methods presented good adsorption performance concerning Ag⁺ and Cu²⁺, Co²⁺ and Ni²⁺. The removal percentages were higher than 90%. In addition, the adsorption capacities were within the literature range. These findings show that the ultrasound technique is not essential to improve the geopolymers production process compared to the conventional process, which generated material with better performance for heavy metals adsorption. Besides, it was possible to aggregate value for fly and bottom ashes, generating promising adsorbent materials.

Application of seed residues from Anadenanthera macrocarpa and Cedrela fissilis as alternative adsorbents for remarkable removal of methylene blue dye in aqueous solutions

Two novel ecological and low-cost adsorbents were prepared from seed residues of the tree species Anadenanthera macrocarpa and Cedrela fissilis for the removal of methylene blue dye in water. The materials were comminuted and characterized by different techniques. The particles of samples have a rough surface with cavities. The optimum dosage and pH for both materials were 1 g L^-1 and pH 8. The pseudo-second-order model was the most suitable for describing the adsorption kinetics for both systems. The Anadenanthera macrocarpa presented a maximum experimental capacity of 228 mg g^-1, while the Cedrela fissilis, a similar capacity of 230 mg g^-1 at 328 K. The Tóth model was proper for describing the equilibrium curves for both systems. The thermodynamic indicators show that the adsorption process is spontaneous and endothermic for both materials. The application of materials for the simulated effluent treatment showed 74 and 78% of color removal using Anadenanthera macrocarpa and Cedrela fissilis samples, respectively. Overall, seed residues of Anadenanthera macrocarpa and Cedrela fissilis could be potentially applied for adsorptive removal of colored contaminants in wastewater.

Utilization of Pacara Earpod tree (Enterolobium contortisilquum) and Ironwood (Caesalpinia leiostachya) seeds as low-cost biosorbents for removal of basic fuchsin

Wastes from the Pacara Earpod tree (Enterolobium contortisilquum) and Ironwood (Caesalpinia leiostachya) seeds were studied as biosorbents for the removal of basic fuchsin from waters. Both biosorbents were prepared and characterized by different analytical methods. The characterization data showed that both materials were mainly composed of lignin, cellulose, and hemicellulose. Both biosorbents exhibited roughened surfaces and surface functional groups such as C-H, C=O, C=C, C-O, C-N, and OH bonds. Furthermore, the XRD pattern shows an amorphous phase with a wide peak from 10 to 30° due to the lignin. In terms of dosage and pH, the use of 1 g L^-1 and 9.0, respectively, is recommended. The initial concentrations for the biosorption kinetics ranged from 50 to 500 mg L^-1, where the Pacara ear and the Ironwood reached an adsorption capacity of 145.62 and 100.743 mg g^-1 for the 500 mg L^-1. The pseudo-second-order was found to be the proper model for describing biosorption of basic fuchsin onto Pacara Earpod tree and Ironwood, respectively. For the isotherm experiments, the maximum experimental biosorption capacity was found to be 166.858 and 110.317 mg g^-1 for the Pacara Earpod and Ironwood for the initial concentration of 500 mg L^-1 at 328 K. The Langmuir and the Tóth models were the best for representing the equilibrium curves for the basic fuchsin on the Pacara Earpod and the Ironwood, respectively. Maximum adsorption capacities of 177.084 mg g^-1 and 136.526 mg g^-1 were achieved for the Pacara Earpod tree and Ironwood, respectively. The biosorption process was spontaneous, endothermic, and favorable for both biosorbents. The biosorbents were also applied for coloration removal of simulated textile effluents, reaching 66% and 54% for the Pacara Earpod and Ironwood, respectively. For the final application, the materials were used in fixed-bed biosorption, with an initial concentration of 200 mg L^-1, reaching breakthrough times of 710 and 415 min, leading to biosorption capacities of the column of 124.5 and 76.5 mg g^-1, for the Pacara Earpod and Ironwood, respectively.

Evaluation of Ocotea puberula bark powder (OPBP) as an effective adsorbent to uptake crystal violet from colored effluents: alternative kinetic approaches

The Ocotea puberula bark powder (OPBP) was evaluated as an effective adsorbent for the removal of crystal violet (CV) from colored effluents. OPBP was characterized and presented a surface with large cavities, organized as a honeycomb. The main functional groups of OPBP were O-H, N-H, C=O, and C-O-C. The adsorption of CV on OPBP was favorable at pH 9 with a dosage of 0.75 g L^-1. The Avrami model was the most suitable to represent the adsorption kinetic profile, being the estimated equilibrium concentration value of 3.37 mg L^-1 for an initial concentration of 50 mg L^-1 (CV removal of 93.3%). The equilibrium was reached within 90 min. The data were better described by the Langmuir isotherm, reaching a maximum adsorption capacity of 444.34 mg g^-1 at 328 K. The Gibbs free energy ranged from - 26.3554 to - 27.8055 kJ mol^-1, and the enthalpy variation was - 11.1519 kJ mol^-1. The external mass transfer was the rate-limiting step, with Biot numbers ranging from 0.0011 to 0.25. Lastly, OPBP application for the treatment of two different simulated effluents was effective, achieving a removal percentage of 90%.

Treatment of water containing methylene by biosorption using Brazilian berry seeds (Eugenia uniflora)

Brazilian berry seeds (Eugenia uniflora) were used as an eco-friendly and low-cost biosorbent for the treatment of textile effluents containing methylene blue. Characterization techniques indicated that Brazilian berry seeds are constituted of irregular particles, mainly composed of lignin and holocellulose groups, distributed in an amorphous structure. Methylene blue biosorption was favorable at pH of 8, using a biosorbent dosage of 0.8 g L^-1. The equilibrium was reached in the first 20 min for lower M methylene blue concentrations and 120 min for higher methylene blue concentrations. Furthermore, the general and pseudo-second-order models were suitable for describing the kinetic data. Langmuir was the most adequate model for describing the isotherm curves, predicting a biosorption capacity of 189.6 mg g^-1 at 328 K. Biosorption was spontaneous (- 9.54 ≤ ΔG⁰ ≤ -8.06 kJ mol^-1) and endothermic, with standard enthalpy change of 6.11 kJ mol^-1. Brazilian berry seeds were successfully used to remove the color of two different simulated textile effluents, achieving 92.2% and 73.5% of removal. Last, the fixed-bed experiment showed that a column packed with Brazilian berry seeds can operate during 840 min, attaining biosorption capacity of 88.7 mg g^-1. The data here presented indicates that textile effluents containing methylene blue can be easily and successfully treated by an eco-friendly and low-cost biosorbent like Brazilian berry seeds.

Araticum (Annona crassiflora) seed powder (ASP) for the treatment of colored effluents by biosorption

Dyes are widely used in many industrial sectors, many contain harmful substances to human health, and their release into the environment entails several environmental problems, generating a major worldwide concern as water resources are increasingly limited. The development of cheap and efficient biosorbents that remove these pollutants is of utmost importance. In this study, powdered seeds of the araticum fruit (Annona crassiflora) were used in the biosorption of crystal violet (CV) dye from aqueous solutions and simulated textile effluents. Through the characterization techniques, it can be observed that the material presented an amorphous structure, containing an irregular surface composed mainly by groups containing carbon, hydrogen, and oxygen. CV biosorption was favored at the natural pH of the solution (7.5) for a dosage of 0.7 g L^-1 of araticum seed powder. The pseudo-second-order model was the most suitable to represent the biosorption kinetics in the removal of the CV. Biosorption capacity reached equilibrium in the first minutes at the lowest concentrations, and, at the highest, after 120 min. The equilibrium data were well represented by the Langmuir model, with a maximum biosorption capacity of 300.96 mg g^-1 at 328 K. Biosorption had a spontaneous and endothermic nature. In the treatment of a simulated effluent, the biosorbent removed 87.8% of the color, proving to be efficient. Therefore, the araticum seeds powder (ASP) can be used as a low-cost material for the treatment of colored effluents containing the crystal violet (CV) dye.

[Single balloon versus Inoue balloon in percutaneous mitral balloon valvuloplasty. Short-term results and complications]

PURPOSE

To assess short-term results and complications of percutaneous mitral balloon valvuloplasty (PMBV) performed with Inoue balloon (IB) and single low profile balloon (SB).

METHODS

We performed 390 PMBV procedures, 29 with IB and 337 with SB. There were no differences in age, sex, echocardiographic score distribution and echocardiographic mitral valve area (MVA).

RESULTS

We performed 29 complete procedures with IB and 330 of 337 in SB group. Comparing IB and pre and pos-PMBV data we obtained: mean pulmonary artery pressure (MPAP) 36 +/- 15 and 39 +/- 14 mmHg, p = 0.2033, mean mitral gradient 17 +/- 6 and 20 +/- 77 mmHg, p = 0.0396 and MVA 0.9 +/- 0.2 and 0.9 +/- 0.2 cm2, p = 0.8043 and pos-PMBV:MPAP 25 +/- 8 and 28 +/- 10 mmHg, p = 0.2881, gradient 5 +/- 3 and 5 +/- 4 mmHg, p = 0.2778 and MVA 2.2 +/- 0.2 and 2.0 +/- 0.4 cm2, p = 0.0362. Mitral valve (MV) was competent in 26 patients in IB and in 280 in SB group and we had +/4 mitral regurgitation in 3 patients in IB and in 57 in SB group (p = 0.3591) pre-PMBV respectively and pos-PMBV there was also no difference in MV competence (p = 0.7439).

CONCLUSION

Both techniques were effective. Hemodynamic data were also similar although MVA was greater in IB group after PMBV.

[Percutaneous mitral valvuloplasty with the single balloon technique. Short-term results, complications and in-hospital follow-up]

PURPOSE

To study the short-term results, complication and in-hospital follow-up of 268 percutaneous mitral balloon valvuloplasty (PMBV) procedures performed with the low-profile monofoil balloon (LPMB) technique from 1990 to 1995.

METHODS

A single 30mm balloon diameter was used in 247 (92.9%) procedures, a single 25mm balloon diameter in 9 (3.3%), a single 25mm balloon followed by a single 30mm balloon diameter in 7 (2.6%) and in 5 procedures a balloon was not used. The mean age group was 36 +/- 12 years. Two hundred nineteen (81.7%) procedures were performed in women (mean age 36 +/- 12 years) and 49 (18.3%) in men (mean age, 35 +/- 14 years) (p = 0.78). Patients were in functional class II (NYHA) in 39 (14.5%), class III in 198 (73.9%) and class IV in 31 (11.6%). Patients were in sinus rhythm in 228 (85.1%) procedures and in atrial fibrillation in 40 (14.9%). The echocardiographic score ranged from 4 to 14 (mean 7.2 +/- 1.5).

RESULTS

There were 256 complete procedures, 249 of which were successful (mitral valve area (MVA) > or = 1.5cm2 after PMBV). Echocardiographic calculated MVA before PMBV was 0.9 +/- 0.2cm2. Hemodynamic calculated MVA before PMBV was 0.9 +/- 0.2cm2 and after was 2.0 +/- 0.4cm2 (p < 0.000001). Mean pulmonary artery pressure decreased from 40 +/- 15mmHg to 28 +/- 10mmHg (p < 0.000001) and mitral mean gradient from 20 +/- 7mmHg to 5 +/- 4mmHg (p < 0.000001). In the 256 complete procedures mitral valve (MV) was competent in 214 and there was 1+ mitral regurgitation (MR) in 42. After PMBV, MV was competent in 166 and there was 1+ MR in 68, 2+ in 16, 3+ in 5 and 4+ MR in 1. There were complications in 14 (5.2%) procedures, severe MR in 6 (3 or 4+), stroke in 2 and cardiac tamponade in 6. Two patients died during emergency cardiac surgery after left ventricular perforation and 1 after stroke.

CONCLUSION

PMBV with the LPMB was an effective procedure with a high success rate and a low rate of complications as the more usual double-balloon and Inoue balloon techniques.

[Percutaneous balloon mitral valvoplasty. Immediate results, complications and hospital outcome]

PURPOSE

To study the short-term results, complications and in-hospital follow-up of 223 percutaneous mitral balloon valvuloplasty (PMBV) procedures (proc)in 219 patients.

METHODS

It was used a single 20mm balloon diameter in 4 proc, double balloon in 7, Inoue balloon in 4 and low profile balloon in 196. The mean-age group was 37.19 years. One hundred eighty three (82.1%) procedures were performed in women (mean age, 36.99 years) and 40 (17.9%) in men (mean age, 38.10 years) (p = 0.63). Patients were in functional class II, (NYHA) in 25 (11.2%) procedures, class III in 165 (74.0%) and class IV in 33 (14.8%). Patients were in sinus rhythm in 182 procedures (81.6%) and in atrial fibrillation in 41 (18.4%). The echocardiographic score range from 4 to 14 (7.4% +/- 1.7). Among 4 and 11 were 98.2% of patients.

RESULTS

We had 203 complete proc and success, mitral valve area (MVA) > or = 1.5cm2 after PMBV in 194 proc. Echocardiographic MVA before PMBV was 0.9 +/- 0.2cm2 and after 1.8 +/- 0.3cm2 (p < 0.01). Hemodynamic measures MVA before PMBV was 0.9 +/- 0.2cm2 and after was 1.9 +/- 0.3cm2 (p < 0.01). Mean pulmonary artery pressure decreased from 39 +/- 14mmHg to 27 +/- 11mmHg (p < 0.01) and mitral mean gradient from 20 +/- 9mmHg to 6 +/- 5mmHg (p < 0.01). In the 203 proc, mitral valve (MV) was competent in 176 and there were 1+ mitral regurgitation (MR) in 27. After PMBV, MV was competent in 126, and there were 1+ MR in 60, 2+ in 10.3+ in 6 and 4+ MR in 1. There was complication in 15 proc, severe MR in 7 (3 or 4+), stroke in 3 and cardiac tamponade in 5. Two patients died during emergency cardiac surgery after left ventricular perforation and one by stroke.

CONCLUSION

PMBV was an effective procedure with a high grade of success and low rate of complication.

[Percutaneous transluminal renal angioplasty in the treatment of renovascular hypertension]

PURPOSE

To analyze the effect of percutaneous transluminal renal angioplasty (PTRA) in renovascular hypertension.

METHODS

Twenty-three patients with renal artery stenosis and arterial hypertension underwent PTRA. There were 11 male and 12 female, 19 to 78 years old (45.8 +/- 17.41). In 20 lesions the diagnosis was atherosclerosis, in 7 fibromuscular dysplasia and in 1 Takayasu arteritis. Three patients underwent bilateral dilatation and 2 patients repeated the procedure due to restenosis. Two patients presented with acute renal failure and severe bilateral renal artery stenosis.

RESULTS

There were 21 technical success in 25 procedures. After 20 satisfactory dilatations, clinical success followed in 17 (100% of cases of fibromuscular dysplasia cases and 77% of atherosclerosis. The fall in diastolic arterial pressure after PTRA was statistical significant (p < 0.001). In two cases acute renal failure the renal function became normal after angioplasty. There were 2 complications and no death attributed to PTRA.

CONCLUSION

The method was effective and safe in the management of renovascular hypertension during the short-term follow-up. It was possible in two cases of acute renal failure to normalize renal function.

[Supravalvular aortic stenosis in two black patients]

Two male black patients, 18 and 12-year-old, with mental retardation and typical elfin face, presented with severe supravalvular aortic stenosis, thus characterizing Williams's or aortic supravalvular stenosis syndrome. Both were submitted to surgical treatment of the stenosis, and are asymptomatic after a one and four years follow-up. For the first time this syndrome, in its classical form, is described in black patients.

[Angioplasty of distal aorta and iliac, femoral, popliteal, renal and subclavian arteries. Early and late results]

PURPOSE

To study the late results of peripheral angioplasty.

PATIENTS AND METHODS

In the period of 8 years from August, 1981 until August, 1989, 27 patients were submitted to 33 procedures of peripheral angioplasty.

RESULTS

There was success in 29 procedures, an insufficient dilatation in 1 and and failure in 3 (2 new attempts were effective). Success rate was 88% of the procedures; clinical and angiographic success was reached in 25 (93%) of the 27 patients. Thirty four obstructions were successful dilated: 12 in renal artery, 12 in common iliac artery, 4 in external iliac artery, 3 in superficial femoral artery, 1 in distal aorta. In the evolution we had a restenosis of a renal artery that was redilated, a precocious occlusion of a common iliac artery (9% of common iliac artery dilatations and 6% of the total of the iliac dilatations) and a popliteal occlusion. Of the 34 dilatations we had a patency of 91% until 2 months.

CONCLUSION

Angioplasty showed to be an effective method with good results in the long term follow-up.