Remígio M. Machado

Copper extraction from ammoniacal medium in a pulsed sieve-plate column with LIX 84-I

This article reports on a study of copper removal from ammoniacal aqueous solution (1.0 kg m(-3) Cu, pH 9.5) by liquid-liquid extraction using a pulsed sieve-plate column. The extractant tested was the hydroxyoxime LIX 84-I (2-hydroxy-5-nonylacetophenone oxime) in the aliphatic diluent Shellsol D-70. The results of the pilot plant experiments demonstrated the feasibility of operating the extraction process in this type of column, with efficiencies of copper removal in the range of 90.5-99.5%. Several effects on the column performance were examined, namely the aqueous and organic flow rates and the pulse velocity. The axial dispersion model was applied to simulate the concentration profiles, which reasonably predicted the experimental data. The overall mass transfer coefficient was evaluated from the experimental data and was found to be between 9×10(-6) and 1.2×10(-5) m s(-1). These data were compared with the ones obtained from the resistances in series model, which indicated that the resistance due to chemical reaction was 84-91% of the overall resistance to mass transfer. The extraction using a hollow fiber contactor was also carried out to compare the membrane process performance with the one of conventional process.

Integrated Process for Biosorption of Copper from Liquid Effluents Using Grape Stalks

A multistage process was used for biosorption of heavy metals from liquid effluents using grape stalks as the biosorbent. The biosorption was carried out with a free biomass suspension in a two-stage, counter-current, stirred batch system. The biomass was separated from the treated effluent using flocculation, sedimentation, and filtering. The filter cake was used, as a small packed column loaded with heavy metals where the elution was performed. The efficiency of the overall system was studied using three synthetic effluents. The first two effluents labeled in this work as F1 and F2 had 10 and 50 ppm of copper, respectively. The third effluent had a complex metal mixture containing 10 ppm of copper, 50 ppm of zinc, 5 ppm of nickel, 100 ppm of calcium, and 100 ppm of sodium. The biosorption system was able to remove 99% of the copper from the F1 effluent (0.08 ppm of copper in the final effluent), using a biomass concentration of 2 g/L. For the F2 effluent, a biomass concentration of 4 g/L was required to obtain a final copper concentration 0.18 ppm. Copper was also removed from the F3 effluent with an efficiency of 98% (final metal concentration of 0.15 ppm). However, it required a biomass concentration of 6 g/L in the two biosorption stages and the other target metals under study, Zn and Ni, had modest removals of 46% and 35%, respectively. The results from the elution experiments demonstrate that the key variables to obtain high metal concentration in the eluate are the metal concentration bounded to the biomass, the superficial velocity of the eluant, and the filter cake depth. Using the F2 effluent to load the biomass up to 12.5 mg/g of copper and performing the elution with a superficial velocity of 0.9 cm/min in a filter cake with depth of 10 cm, a copper concentration in the eluate of 1.8 g/L was achieved, which correspond to a concentration factor of 38-fold.

A study on a combined process for the treatment of phenolic resin plant effluents

The removal of phenol and formaldehyde from phenolic resin plant effluents has been studied by using a combined process. In the first step, phenol was removed from effluent by solvent extraction. Special attention was paid to the effluent with a low content of phenol, which was treated by non-dispersive solvent extraction in hollow fibres. It was found that a single module of Liqui-Cel 2.5in. x 8in. membrane contactor allowed processing approximately 24 L/h of effluent with 0.4-0.7 g/L phenol and attaining values as low as 0.5 mg/L in the raffinate. Formaldehyde, which was left in phenolic resin plant effluent after the removal of phenol, has been treated with hydrogen peroxide in alkaline medium and also in acidic medium (Fenton process). In alkaline medium, formaldehyde was oxidized with hydrogen peroxide to formate ion, which was recovered by solvent extraction. The oxidation of formaldehyde with Fenton process was also studied under several operating conditions. It was found that a large amount of hydrogen peroxide (i.e. mole ratio H(2)O(2):HCHO>6) was necessary to mineralize more than 90% HCHO in 1-2h, at atmospheric pressure and 25 degrees C. The combination of pressure and high temperature strongly increased the kinetics of the process and allowed achieving a very high overall efficiency of the treatment under moderate H(2)O(2) dosage.

Recovery of hydrochloric acid from galvanizing industrial effluents

ABSTRACT The recovery of hydrochloric acid and its separation from iron, zinc and minor elements, in the galvanizing pickling baths, were studied by solvent extraction (SX) and distillation and by distillation and crystallization. Several extractants were tested, the tri-isooctyl amine, Alamine 308, the primary aliphatic amine Primene JM-T and the mixture of four trialkylphosphine oxides, Cyanex 923. Only Cyanex 923 enabled distillation. The results indicated the feasibility of the processes to treat a real effluent using Cyanex 923 and to obtain high HCl concentrations in the distillate (256–330 g/L).

Selective Separation and Recovery of Zinc and Lead from Galvanizing Industrial Effluents by Anion Exchange

The recovery of zinc and its separation from iron, hydrochloric acid, and minor elements in the galvanizing pickling baths were studied by anion exchange. The breakthrough curves demonstrated that the resins, Lewatit MonoPlus MP 500 and AMBERLYST A21, exhibit a greater capacity for zinc than for cadmium, copper, and lead. The results indicated the feasibility of operating the ion exchange process to treat a real effluent. During the loading, lead started eluting until its complete removal from the resin. Like this, a two-step removal solution is proposed, using two columns with Lewatit MonoPlus MP 500, for separating zinc and lead.

BIOSORPTION OF COPPER, ZINC AND NICKEL BY GRAPE- STALKS AND CORK BIOMASSES

The removal of copper, zinc and nickel from aqueous solutions by biosorption using grapestalks and cork biomasses is reported. The adsorption isotherms were determined and the uptake capacity for copper with grape stalks and cork was, respectively, 19.9 mg/g and 16.5 mg/g, while for zinc was 18.3mg/g with grape stalks and 13.4 mg/g with cork and for nickel was 11.1 mg/g with cork. The kinetics of copper biosorption in both biomasses was studied and a second order model was fitted to the experimental data. Copper biosorption is a fast process and within the first 5 minutes 80% of the maximum capacity was attained. The calculated activation energy for the biosorption reaction of copper was 28±3 KJ/mol for grape stalks and 6±2 KJ/mol for cork biomass. These low values indicate that the metal diffusion inside the particles is the rate controlling step of the reaction.

Dewatering of brewer’s spent grain using an integrated membrane filter press with vacuum drying capabilities

ABSTRACT Brewer’s spent grain (BSG) is a by-product of the brewing process, rich in fiber, protein and carbohydrates. Its potential application is limited because of high moisture content (80%). This work presents a process for dewatering BSG using two different sets of membrane filter plates in a filter press with vacuum drying: recessive plates with polypropylene membranes and the innovative Rollfit® plates. A final moisture content of 12-15% was obtained in 15 mm-thick filter cakes, using both types of plates. The dewatering cycle included filtration, membrane-squeezing, and vacuum thermal drying using hot water (~90ºC) as heat source.