Franco Medici

Inertization of toxic metals in cement matrices: Effects on hydration, setting and hardening

Abstract The effect of the addition of four toxic metals added as chloride solutions and suspensions to a cementitious matrix, consisting of white cement paste and mortar, was studied. To such purpose variations in the physical-mechanical properties of the cement mixes, the development of the heat over time and the evolution of the phases formed during hydration were observed.

Thermal treatment for recovery of manganese and zinc from zinc-carbon and alkaline spent batteries

The aim of this paper is the recovery of manganese and zinc from a mixture of zinc-carbon and alkaline spent batteries, containing 40.9% of Mn and 30.1% of Zn, after preliminary physical treatment followed by removal of mercury. Separation of the metals has been carried out on the basis of their different boiling points, being 357°C and 906°C the boiling point of mercury and zinc and 1564°C the melting point of Mn(2)O(3). Characterization by chemical analysis, TGA/DTA and X-ray powder diffraction of the mixture has been carried out after comminution sieving and shaking table treatment to remove the anodic collectors and most of chlorides contained in the mixture. The mixture has been roasted at various temperatures and resident times in a flow of air to set the best conditions to remove mercury that were 400°C and 10 min. After that, the flow of air has been turned into a nitrogen one (inert atmosphere) and the temperatures raised, thus permitting the zinc oxide to be reduced to metallic zinc by the carbon present in the original mixture and recovered after volatilization as a high grade concentrate, while manganese was left in the residue. The recovery and the grade of the two metals, at 1000°C and 30 min residence time, were 84% and 100% for zinc and 85% and 63% for manganese, respectively. The recovery of zinc increased to 99% with a grade of 97% at 1200°C and 30 min residence time, while the recovery and grade of manganese were 86% and 87%, respectively, at that temperature. Moreover, the chlorinated compounds that could form by the combustion of the plastics contained in the spent batteries, are destroyed at the temperature required by the process.

Fluoride Removal from Water by Adsorption on a High Alumina Content Bauxite

Drinking water contamination by fluoride is recognized as a major public health problem in many parts of the world. In fact, although fluoride is an essential trace element for animals and humans, excessive fluoride intake may cause adverse health effects. In this study we investigated the potential of a natural, high alumina content, bauxite for the removal of fluoride from contaminated water. Both batch and continuous experiments were performed. In continuous-flow column experiments, the effects of inlet fluoride concentration (5–50 mg L

Behaviour of polyaminophenolic additives in the granulation of lime and fly-ash

Abstract Room temperature granulation of fly-ash generated from incineration of municipal solid wastes (MSW) was achieved by mixing the ash with lime, water and three polyaminophenolic additives in a rotating drum. The presence of the additives favours the carbonation of lime, thus accelerating and enhancing the development of short-term compressive strength of the granules; this ensures there is no need to cure the pastes in CO 2 -enriched or heated atmospheres. After curing in air for 30, 45, 60 and 90 days, the granules were evaluated by unconfined compressive strength tests. The strengths achieved shortly after granulation allow safe transportation and storage of the granules and are similar to the strengths of the light granulates used for building purposes.

Use of cell wall degrading enzymes for the production of high-quality functional products from tomato processing waste

The feasibility of using tomato pomace, the solid waste resulting from the industrial processing of tomatoes, to produce a tomato oleoresin and a lycopene-enriched seed oil was investigated. The oil was obtained by cold-pressing the seeds, while the oleoresin was produced by pretreating the peel fraction of the waste with cell wall degrading enzymes. The latter consisted of polygalacturonase, pectin methylesterase, cellulase and hemicellulase. The enzymatic treatment followed by hexane extraction and solvent evaporation allowed the production of an oleoresin with a lycopene content of about 7% by weight. The oleoresin was incorporated in different proportions into tomato seed oil so as to obtain a functional oil with a lycopene content ranging from 30 to 600 ppm. The lycopene-enriched oil was characterized by official analytical methods and its potential use in the nutraceutical and cosmetic sectors was discussed.

Spent Tea Leaves as a Potential Low-cost Adsorbent for the Removal of Azo Dyes from Wastewater

Spent tea leaves (STL), a solid waste that is available in large amounts worldwide, was investigated as a potential low-cost adsorbent for the removal of two azo dyes, Reactive Green 19 (RG19) and Reactive Violet 5 (RV5), from contaminated waters. Preliminary experiments conducted on untreated STL showed that this material exhibited very low removal efficiencies (<10 %). By contrast, thermal activation of STL (200 to 400 °C for up to 2 h) resulted in a significant increase in dye adsorption. After thermal exposure of STL to 300 °C for 1 hour, removal efficiencies of 98.8 % and 72.8 % were observed, respectively, for RG19 and RV5. Characterization of the adsorbent by TG/DTA and FTIR measurements showed that structural and chemical changes occurred in the lignocellulosic material which were probably responsible for the enhancement in adsorption capacity. These results strongly support the use of activated STL as a low-cost alternative to conventional adsorbents.

Assessment of the leaching of metallic elements in the technology of solidification in aqueous solution

Results are presented of experiments performed to optimize the solidification/stabilization system for metallic elements in aqueous solution. This system involves mixing cement and a solution of metallic elements in a conventional mixer: the paste thus obtained is transferred drop by drop into a recipient filled with an aqueous solution of NaOH at 20% by weight, in which it solidifies immediately. The separate use of chloride solutions of Li+, Cr3+, Pb2+ and Zn2+ makes it possible to obtain granules displaying various levels of compressive strength. Three different inertization matrices were used in the experiments, the first consisting solely of Portland cement, the second of Portland cement and a superplasticizer additive, and the third of Portland cement partially replaced with silica-fume and superplasticizer. The results of the tests performed showed a very low level of leaching into the alkaline solidification solution for Cr3+, the quantity leached being under 2% as against higher levels for the other metallic elements. For all the considered elements, the best results were obtained by using silica-fume in the inertization matrix.

Poly-Amino-Phenolic Additives Accelerating the Carbonation of Hydrated Lime in Mortar

Preliminary tests were carried out to evaluate the influence of poly-amino-phenolic (PAP) oligomers on the absorption of CO2 from air into aqueous saturated solution of Ca(OH)2. Further experiments were then conducted by employing the best additive (PAP2), to facilitate the carbonation of hydrated lime mortars and to identify the most favorable additive content. Mechanical tests and results obtained by infrared spectra suggests that this additive behaves better in accepting, transferring, and giving up CO2 to the lime.

Recovery of copper from contaminated soil by flushing

In this work the development of a process for the recovery of copper from contaminated industrial soils is presented. Experimental tests on a standard soil contaminated with a solution of copper chloride were carried out. The metal was extracted from the contaminated soil by flushing with a 0.1 M aqueous solution of an ethylenediaminetetraacetic acid (EDTA) sodium salt. A maximum copper extraction efficiency of about 60% was observed. Copper was then separated from the extracted solution by precipitation with sodium hydroxide after addition of ferric sulfate.

Lead Removal from Water by Adsorption on Spent Coffee Grounds

Industrial water and drinking water contamination by lead is recognized as a public health problem in several countries of the world, including Italy. Lead is on the second position on the Agency for Toxic Substances and Disease Registry (ATSDR) list for dangerous elements. The Environmental Protection Agency (EPA) has also recognized lead as a probable human carcinogen. In this study the potential of spent coffee grounds (SCG) for the removal of lead from contaminated water was investigated. Batch experiments were performed at 25 °C on untreated SCG. The results obtained showed that the adsorption equilibrium of lead on SCG is well described by the Langmuir equation, with a maximum adsorption capacity of 2.46 mg g. Overall, this study strongly supports the use of SCG for the removal of lead, and probably of other metal species, from industrial and drinking waters.