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The removal of dyes from wastewater is an important topic in environmental applications. Methylene blue (MB) is one of the most worrisome compounds, as it is widespread and used in many industrial activities. Adsorption represents an effective technique for the removal of this contaminant. Thermo plasma expanded graphite (TPEG) is an industrial material characterized by a fibrous morphology, a very low density and overlapped graphene layers. TPEG has a higher specific surface compared to conventional thermo-expanded graphite and it can establish effective attractive forces with charged pollutants. These properties make TPEG a very promising adsorbent material. In the present work, TPEG was tested in an innovative multilayer column system to treat MB contaminated solutions. Several batch experiments were carried out by varying pH, initial MB concentration and temperature. The optimal adsorption performance was assessed at pH 11, around which the TPEG assumed the maximum negative charge. Based on these results, the adsorption mechanism appeared to be related mainly to electrostatic interactions. At room temperature, the greatest amount of MB adsorbed on TPEG was detected by treating solutions with an initial concentration of 30 mgMB/L. The temperature increase from 20 to 40 °C caused an enhanced adsorption capacity when concentrations higher than 10 mgMB/L were treated. The adsorption trends were accurately described by a pseudo-second order kinetic law and the adsorption isotherms at 20 and 40 °C were found to follow both the features of Freundlich and Langmuir models. The adsorption capacity was estimated to reach threshold values around 95 mgMB/gTPEG and 265 mgMB/gTPEG at 20 and 40°C, respectively. The Gibbs energy change (ΔG°) was calculated to about −7.80 kJ/mol, which proved that the process is spontaneous from a thermodynamic point of view. Finally, it was verified that TPEG can be efficiently reused 5 times after a simple chemical regeneration phase with HCl.
Alessio Siciliano; Giulia Maria Curcio; Carlo Limonti; Salvatore Masi; Michele Greco. Methylene blue adsorption on thermo plasma expanded graphite in a multilayer column system. Journal of Environmental Management 2021, 296, 113365 .
AMA StyleAlessio Siciliano, Giulia Maria Curcio, Carlo Limonti, Salvatore Masi, Michele Greco. Methylene blue adsorption on thermo plasma expanded graphite in a multilayer column system. Journal of Environmental Management. 2021; 296 ():113365.
Chicago/Turabian StyleAlessio Siciliano; Giulia Maria Curcio; Carlo Limonti; Salvatore Masi; Michele Greco. 2021. "Methylene blue adsorption on thermo plasma expanded graphite in a multilayer column system." Journal of Environmental Management 296, no. : 113365.
The discharge of hexavalent chromium in aquatic environments represents an issue of great concern. The chemical reduction of Cr6+ to Cr3+, which is less mobile and harmful, is a suitable approach for chromium removal. In this regard, in comparison to other reactive metals, the use of zero-valent magnesium (ZVM) has several advantages. Nevertheless, this element has been scarcely investigated in the decontamination of water and wastewater. In particular, no studies have been conducted by applying Mg0 particles fixed in column systems for Cr6+ reduction. In the present study, a wide experimental investigation was carried out to analyse the chromium abatement through zero valent magnesium particles in a packed batch column. The effects of pH, initial Cr6+ concentration and temperature were investigated. The experimental results proved that the process performances were mainly affected by pH values. High efficiencies were detected at pH 3, while unsatisfactory abatements were observed at pH 5 and under uncontrolled pH conditions. At pH 3, the process performance worsened with the rise in the initial chromium concentration. In particular, a complete abatement was detected in 180 min by treating solutions with initial Cr6+ concentrations up to 40 mg/L. The effect of temperature was negligible at pH 3 and under uncontrolled pH, while the increase from 20 to 30 and 40 °C produced a significant improvement in the removal yields at pH 5. By means of a kinetic analysis a theoretical law able to accurately describe the experimental removal trends was identified. Furthermore, a mathematical relation between the observed kinetic constants and the magnesium to initial chromium amount ratio was defined. Finally, the reaction pathways were proposed, and the reaction products identified.
Alessio Siciliano; Giulia Maria Curcio; Carlo Limonti. Hexavalent chromium reduction by zero-valent magnesium particles in column systems. Journal of Environmental Management 2021, 293, 112905 .
AMA StyleAlessio Siciliano, Giulia Maria Curcio, Carlo Limonti. Hexavalent chromium reduction by zero-valent magnesium particles in column systems. Journal of Environmental Management. 2021; 293 ():112905.
Chicago/Turabian StyleAlessio Siciliano; Giulia Maria Curcio; Carlo Limonti. 2021. "Hexavalent chromium reduction by zero-valent magnesium particles in column systems." Journal of Environmental Management 293, no. : 112905.
Anaerobic digestion (AD) represents a suitable option for the management of the waste-activated sludge (WAS) produced in municipal wastewater treatment plants. Nevertheless, due to its complex characteristics, WAS is often barely degradable under conventional anaerobic processes. The use of conductive materials during AD provides a promising route for enhancing WAS digestion, through the effects of direct inter-species electron transfer (DIET). The present paper aims to evaluate the effects of the addition of four different materials—granular activated carbon (GAC), granular iron, and aluminium and steel scrap powders—in semi-continuous lab-scale reactors under very high volatile fatty acids-to-alkalinity ratios. In particular, the use of metallic aluminium in WAS digestion was investigated for the first time and compared to the other materials. The AD of WAS without the addition of conductive materials was impossible, while the use of steel powder and zero-valent iron is shown not to improve the digestion process in a satisfactory way. On the contrary, both GAC and Al allow for effective WAS degradation. At stable conditions, methane yields of about 230 NmLCH4/gVS and 212 NmLCH4/gVS are recorded for GAC- and Al-amended reactors, respectively. These two materials are the most promising in sustaining WAS AD through DIET also in case of unbalanced volatile fatty acids-to-alkalinity ratios.
Paolo Calabrò; Filippo Fazzino; Carlo Limonti; Alessio Siciliano. Enhancement of Anaerobic Digestion of Waste-Activated Sludge by Conductive Materials under High Volatile Fatty Acids-to-Alkalinity Ratios. Water 2021, 13, 391 .
AMA StylePaolo Calabrò, Filippo Fazzino, Carlo Limonti, Alessio Siciliano. Enhancement of Anaerobic Digestion of Waste-Activated Sludge by Conductive Materials under High Volatile Fatty Acids-to-Alkalinity Ratios. Water. 2021; 13 (4):391.
Chicago/Turabian StylePaolo Calabrò; Filippo Fazzino; Carlo Limonti; Alessio Siciliano. 2021. "Enhancement of Anaerobic Digestion of Waste-Activated Sludge by Conductive Materials under High Volatile Fatty Acids-to-Alkalinity Ratios." Water 13, no. 4: 391.
The abatement of nutrient compounds from aqueous waste and wastewater is currently a priority issue. Indeed, the uncontrolled discharge of high levels of nutrients into water bodies causes serious deteriorations of environmental quality. On the other hand, the increasing request of nutrient compounds for agronomic utilizations makes it strictly necessary to identify technologies able to recover the nutrients from wastewater streams so as to avoid the consumption of natural resources. In this regard, the removal and recovery of nitrogen and phosphorus from aqueous waste and wastewater as struvite (MgNH4PO4·6H2O) represents an attractive approach. Indeed, through the struvite precipitation it is possible to effectively remove the ammonium and phosphate content of many types of wastewater and to produce a solid compound, with only a trace of impurities. This precipitate, due to its chemical characteristics, represents a valuable multi-nutrients slow release fertilizer for vegetables and plants growth. For these reasons, the struvite precipitation technology constantly progresses on several aspects of the process. This manuscript provides a comprehensive review on the recent developments in this technology for the removal and recovery of nutrients from aqueous waste and wastewater. The theoretical background, the parameters, and the operating conditions affecting the process evolution are initially presented. After that, the paper focuses on the reagents exploitable to promote the process performance, with particular regard to unconventional low-cost compounds. In addition, the development of reactors configurations, the main technologies implemented on field scale, as well as the recent works on the use of struvite in agronomic practices are presented.
Alessio Siciliano; Carlo Limonti; Giulia Maria Curcio; Raffaele Molinari. Advances in Struvite Precipitation Technologies for Nutrients Removal and Recovery from Aqueous Waste and Wastewater. Sustainability 2020, 12, 7538 .
AMA StyleAlessio Siciliano, Carlo Limonti, Giulia Maria Curcio, Raffaele Molinari. Advances in Struvite Precipitation Technologies for Nutrients Removal and Recovery from Aqueous Waste and Wastewater. Sustainability. 2020; 12 (18):7538.
Chicago/Turabian StyleAlessio Siciliano; Carlo Limonti; Giulia Maria Curcio; Raffaele Molinari. 2020. "Advances in Struvite Precipitation Technologies for Nutrients Removal and Recovery from Aqueous Waste and Wastewater." Sustainability 12, no. 18: 7538.
The removal of nitrate from aqueous environments through zero-valent metallic elements is an attractive technique that has gained increasing interest in recent years. In comparison to other metallic elements, zero-valent magnesium (ZVM) has numerous beneficial aspects. Nevertheless, the use of Mg0 particles for nitrate reduction in column systems has not been investigated yet. To overcome the lack of research, in the present study, a wide experimental activity was carried out to develop a chemical denitrification process through ZVM in batch column equipment. Several tests were executed to evaluate the effects of recirculation hydraulic velocity, pH, Mg0 amount, N-NO3− initial concentration and temperature on the process performance. The results show that the process efficiency is positively influenced by the recirculation velocity increase. In particular, the optimal condition was detected with a value of 1 m/min. The process pH was identified as the main operating parameter. At pH 3, abatements higher than 86.6% were reached for every initial nitrate concentration tested. In these conditions, nitrogen gas was detected as the main reaction product. The pH increase up to values of 5 and 7 caused a drastic denitrification decline with observed efficiencies below 26%. At pH 3, the ratio (RMN) between Mg0 and initial nitrate amount also plays a key role in the treatment performance. A characteristic value of about RMN = 0.333 gMg0/mgN-NO3− was found with which it is possible to reach the maximum reaction rate. Unexpectedly, the process was negatively affected by the increase in temperature from 20 to 40 °C. At 20 °C, the material showed satisfactory denitrification efficiencies in subsequent reuse cycles. With the optimal RMN ratio, removals up to 90% were detected by reusing the reactive material three times. By means of a kinetic analysis, a mathematical law able to describe the nitrate abatement curves was defined. Moreover, the relation between the observed kinetic constant and the operating parameters was recognized. Finally, the reaction pathways were proposed and the corrosion reaction products formed during the treatment were identified.
Alessio Siciliano; Giulia Maria Curcio; Carlo Limonti. Chemical Denitrification with Mg0 Particles in Column Systems. Sustainability 2020, 12, 2984 .
AMA StyleAlessio Siciliano, Giulia Maria Curcio, Carlo Limonti. Chemical Denitrification with Mg0 Particles in Column Systems. Sustainability. 2020; 12 (7):2984.
Chicago/Turabian StyleAlessio Siciliano; Giulia Maria Curcio; Carlo Limonti. 2020. "Chemical Denitrification with Mg0 Particles in Column Systems." Sustainability 12, no. 7: 2984.
The composting process of organic fraction of municipal solid waste, besides to the residual compost, generates a wastewater that is characterized by a high organic load. The application of anaerobic processes represents an advantageous solution for the treatment and valorization of this type of wastewater. Nevertheless, few works have been focused on the anaerobic digestion of compost leachate. To overcome this dearth, in the present paper an extensive experimental investigation was carried out to develop and analyse the anaerobic treatment of young leachate in completely stirred tank reactors (CSTR). Initially, it was defined a suitable leachate pretreatment to correct its acidic characteristics that is potentially able to inhibit methanogenic biomass activity. The pretreated leachate was fed to the digester over the start-up phase that was completed in about 40 days. During the operational period, the organic load rate (OLR) changed between 4.25 kgCOD/m3d and 38.5 kgCOD/m3d. The chemical oxygen demand (COD) abatement was higher than 90% for OLR values up to 14.5 kgCOD/m3d and around to 80% for applied loads equal to 24.5 kgCOD/m3d. At this OLR, it was reached the maximum daily biogas production of about 9.3 Lbiogas/(Lreactord). The CH4 fraction was between 70%–78% and the methane production yield in the range 0.34–0.38 LCH4/gCODremoved. The deterioration of biogas production started for OLR values that were over the threshold of 24.5 kgCOD/m3d when a volatile fatty acids (VFA) accumulation occurred and the pH dropped below 6.5. The maximum ratio between VFA and alkalinity (ALK) tolerable in the CSTR was identified to be 0.5 gCH3COOH/gCaCO3. Through an economic analysis, it was proven that the digestion of compost leachate could ensure significant economic profits. Furthermore, the produced digestate had characteristics that were compatible for agricultural applications.
Alessio Siciliano; Carlo Limonti; Giulia Maria Curcio; Vincenza Calabrò. Biogas Generation through Anaerobic Digestion of Compost Leachate in Semi-Continuous Completely Stirred Tank Reactors. Processes 2019, 7, 635 .
AMA StyleAlessio Siciliano, Carlo Limonti, Giulia Maria Curcio, Vincenza Calabrò. Biogas Generation through Anaerobic Digestion of Compost Leachate in Semi-Continuous Completely Stirred Tank Reactors. Processes. 2019; 7 (9):635.
Chicago/Turabian StyleAlessio Siciliano; Carlo Limonti; Giulia Maria Curcio; Vincenza Calabrò. 2019. "Biogas Generation through Anaerobic Digestion of Compost Leachate in Semi-Continuous Completely Stirred Tank Reactors." Processes 7, no. 9: 635.
The pollution of water by nitrates represents an important environmental and health issue. The development of sustainable technologies that are able to efficiently remove this contaminant is a key challenge in the field of wastewater treatment. Chemical denitrification by means of zero-valent metallic elements is an interesting method to reduce the oxidized forms of nitrogen. Compared to other metallic reactants, zero-valent magnesium (ZVM) has many profitable aspects, but its use for nitrate removal has scarcely been investigated. In the present work, several batch tests were conducted to examine the concurrent effects of pH, initial nitrate concentration and Mg0 quantity on process performance. The experimental results proved that at pH 3, for a given initial nitrate concentration, the dose of ZVM largely influences process efficiency. In particular, with a ratio between Mg0 and initial N-NO3− amount (Mg/NNi) of 0.33 g/mg, it is possible to obtain complete denitrification within 30 min. Beyond this ratio, no further improvement of treatment was observed. The experiments allowed us to identify the nitrogen forms produced during the treatment. Nitrogen gas was generally the main reaction product, but the trends of the different compounds (NO3−, NO2−, NH4+ and N2) notably changed in response to the modification of operating parameters. Moreover, the results demonstrated that, in a highly acidic environment, when treating solutions with a low nitrate concentration, process performances are unsatisfactory even when using a high Mg/NNi ratio. By increasing the process pH to 5 and 7, a significant denitrification decline occurred. Furthermore, at these pH levels, the enhancement of nitrate concentration caused a progressive process deterioration. Through detailed analysis of experimental results, reactions kinetics and new mathematical equations, able to describe the trends of different nitrogen forms, have been defined. Moreover, reactions pathways have been proposed. Finally, the characterization of exhausted material allowed us to identify the corrosion products formed during the treatment.
Alessio Siciliano; Giulia Maria Curcio; Carlo Limonti. Experimental Analysis and Modeling of Nitrate Removal through Zero-Valent Magnesium Particles. Water 2019, 11, 1276 .
AMA StyleAlessio Siciliano, Giulia Maria Curcio, Carlo Limonti. Experimental Analysis and Modeling of Nitrate Removal through Zero-Valent Magnesium Particles. Water. 2019; 11 (6):1276.
Chicago/Turabian StyleAlessio Siciliano; Giulia Maria Curcio; Carlo Limonti. 2019. "Experimental Analysis and Modeling of Nitrate Removal through Zero-Valent Magnesium Particles." Water 11, no. 6: 1276.
The present study aimed to develop an integrated treatment of agro-industrial waste for biofuel (biogas and syngas) production and for phosphorus recovery. In the first step, an anaerobic digestion (AD) process was carried out on two different mixtures of raw agro-industrial residues. Specifically, a mixture of asparagus and tomato wastes (mixture-1) and a mixture of potatoes and kiwifruit residues (mixture-2) were investigated. The results proved that the properties of mixtures notably affect the evolution of the digestion process. Indeed, despite the lower organic load, the maximum biogas yield, of about 0.44 L/gCODremoved, was obtained for mixture-1. For mixture-2, the digestion process was hindered by the accumulation of acidity due to the lack of alkalinity in respect to the amount of volatile fatty acids. In the second step, the digestates from AD were utilized for syngas production using supercritical water gasification (SCWG) at 450 °C and 250 bar. Both the digestates were rapidly converted into syngas, which was mainly composed of H2, CO2, CH4, and CO. The maximum values of global gasification efficiency, equal to 56.5 g/kgCOD, and gas yield, equal to 1.8 mol/kgTS, were detected for mixture-2. The last step of the integrated treatment aimed to recover the phosphorus content, in the form of MgKPO4ˑ6H2O, from the residual liquid fraction of SCWG. The experimental results proved that at pH = 10 and Mg/P = 1 it is possible to obtain almost complete phosphorus removal. Moreover, by using the scanning electronic microscopy, it was demonstrated that the produced precipitate was effectively composed of magnesium potassium phosphate crystals.
Alessio Siciliano; Carlo Limonti; Sanjeet Mehariya; Antonio Molino; Vincenza Calabrò. Biofuel Production and Phosphorus Recovery through an Integrated Treatment of Agro-Industrial Waste. Sustainability 2018, 11, 52 .
AMA StyleAlessio Siciliano, Carlo Limonti, Sanjeet Mehariya, Antonio Molino, Vincenza Calabrò. Biofuel Production and Phosphorus Recovery through an Integrated Treatment of Agro-Industrial Waste. Sustainability. 2018; 11 (1):52.
Chicago/Turabian StyleAlessio Siciliano; Carlo Limonti; Sanjeet Mehariya; Antonio Molino; Vincenza Calabrò. 2018. "Biofuel Production and Phosphorus Recovery through an Integrated Treatment of Agro-Industrial Waste." Sustainability 11, no. 1: 52.
Lead is one of the most toxic heavy metals that can create a severe risk to water ecosystem health. Zero-valent iron is an effective material for Pb2+ removal treatments. In particular, nanoscopic zero-valent iron (nZVI) particles are characterized by high reaction rates; nevertheless, their utilization in water and groundwater remediation techniques requires further investigations. Indeed, it is necessary to define effective methods able to avoid the drawbacks due to the aggregation tendency of nanoparticles and their potential uncontrolled transport in groundwater. In this work, nZVI was supported on magnesium oxide grains (MgO_nZVI) to synthesize an alternative material for lead removal from aqueous solutions. Many experiments were conducted under several operating conditions in order to analyze the effectiveness of the produced material in Pb2+ abatement. The performance of MgO_nZVI was also compared with those detected using commercial microscopic Fe0 (mZVI) as a reactive material. The experimental findings showed a much greater reactivity of the supported nanoscopic iron particles. By means of a kinetic analysis of batch tests results, it was verified that, both for MgO_nZVI and mZVI, the lead abatement follows a pseudo-second-order kinetic law. The reaction rates were affected by the initial pH of the treatment solution and by the ratio between the Fe0 amount and initial lead concentration. The efficiency of MgO_nZVI in a continuous test was steadily around 97.5% for about 1000 exchanged pore volumes (PV) of reactive material, while by using mZVI, the lead removal was approximately 88% for about 600 PV. X-ray diffraction (XRD) and energy-dispersive spectroscopy EDS analyses suggested the formation of typical iron corrosion products and the presence of metallic lead Pb0 and Pb2+ compounds on exhausted materials.
Alessio Siciliano; Carlo Limonti. Nanoscopic Zero-Valent Iron Supported on MgO for Lead Removal from Waters. Water 2018, 10, 404 .
AMA StyleAlessio Siciliano, Carlo Limonti. Nanoscopic Zero-Valent Iron Supported on MgO for Lead Removal from Waters. Water. 2018; 10 (4):404.
Chicago/Turabian StyleAlessio Siciliano; Carlo Limonti. 2018. "Nanoscopic Zero-Valent Iron Supported on MgO for Lead Removal from Waters." Water 10, no. 4: 404.
The treatment of landfill leachate, due to its great polluting load, is a very difficult task. In particular, the abatement of high ammonium concentrations represents one of the main issues. Among the available techniques, struvite precipitation is an effective method for the removal and recovery of NH4+ load. However, due to the lack of phosphorus and magnesium amounts, the struvite formation results in an expensive process in the leachate treatment. To overcome this issue, in the present work, we developed a simple and suitable method for ammonium removal by the multiple recycling of struvite decomposition residues. In this regard, a procedure for acid dissolution of struvite, produced by using industrial grade reagents, was initially defined. The effect of pH, temperature, and acid type was investigated. The experimental results proved the effectiveness of both hydrochloric and acetic acid, which allow a high and selective release of ammonium at T = 50 °C and pH = 5.5. The multiple reuse of decomposition products, combined with the supplementation of a small quantity of phosphorus and magnesium at molar ratios of n(N):n(Mg):n(P) = 1:0.05:0.05, guarantees stable NH4+ abatement of about 82%. The proposed process allows a cost saving of around to 74% and can be easily applied in industrial treatment plants.
Alessio Siciliano; Maria Assuntina Stillitano; Carlo Limonti; Francesco Marchio. Ammonium Removal from Landfill Leachate by Means of Multiple Recycling of Struvite Residues Obtained through Acid Decomposition. Applied Sciences 2016, 6, 375 .
AMA StyleAlessio Siciliano, Maria Assuntina Stillitano, Carlo Limonti, Francesco Marchio. Ammonium Removal from Landfill Leachate by Means of Multiple Recycling of Struvite Residues Obtained through Acid Decomposition. Applied Sciences. 2016; 6 (11):375.
Chicago/Turabian StyleAlessio Siciliano; Maria Assuntina Stillitano; Carlo Limonti; Francesco Marchio. 2016. "Ammonium Removal from Landfill Leachate by Means of Multiple Recycling of Struvite Residues Obtained through Acid Decomposition." Applied Sciences 6, no. 11: 375.
In the Mediterranean region, the disposal of residues of olive oil industries represents an important environmental issue. In recent years, many techniques were proposed to improve the characteristics of these wastes with the aim to use them for methane generation in anaerobic digestion processes. Nevertheless, these techniques, in many cases, result costly as well as difficult to perform. In the present work, a simple and useful process that exploits H2O2 in conjunction with lime is developed to enhance the anaerobic biodegradability of wet olive mill wastes (WMOW). Several tests were performed to investigate the influence of lime amount and H2O2 addition modality. The treatment efficiency was positively affected by the increase of lime dosage and by the sequential addition of hydrogen peroxide. The developed process allows reaching phenols abatements up to 80% and volatile fatty acids productions up to 90% by using H2O2 and Ca(OH)2 amounts of 0.05 gH2O2/gCOD and 35 g/L, respectively. The results of many batch anaerobic digestion tests, carried out by means of laboratory equipment, proved that the biogas production from fresh wet olive mill wastes is hardly achievable. On the contrary, organic matter abatements, around to 78%, and great methane yields, up to 0.34–0.35 LCH4/gCODremoved, were obtained on pretreated wastes.
Alessio Siciliano; Maria Assuntina Stillitano; Carlo Limonti. Energetic Valorization of Wet Olive Mill Wastes through a Suitable Integrated Treatment: H2O2 with Lime and Anaerobic Digestion. Sustainability 2016, 8, 1150 .
AMA StyleAlessio Siciliano, Maria Assuntina Stillitano, Carlo Limonti. Energetic Valorization of Wet Olive Mill Wastes through a Suitable Integrated Treatment: H2O2 with Lime and Anaerobic Digestion. Sustainability. 2016; 8 (11):1150.
Chicago/Turabian StyleAlessio Siciliano; Maria Assuntina Stillitano; Carlo Limonti. 2016. "Energetic Valorization of Wet Olive Mill Wastes through a Suitable Integrated Treatment: H2O2 with Lime and Anaerobic Digestion." Sustainability 8, no. 11: 1150.