Search

The thermal behavior of some types of raw and lead-polluted biomasses typical in south Spain was studied by non-isothermal thermogravimetry. Experiments were carried out in nitrogen atmosphere at three heating rates (5, 10 and 20°C/min). The results of thermogravimetric tests carried out proved that the presence of lead did not change the main degradation pathways of selected biomass (almond shell (AS) and olive pomace (OP)). However, from a point of view of mass loss, lead-polluted samples showed higher decomposition temperatures and decomposition at higher rate. The determination of activation energies was performed by isoconversional methods of Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Friedman (FR). In general, lead-polluted samples showed lower activation energies than raw ones. Then, Coast-Redfern method was applied to determine kinetic function. The kinetic function that seems to determine the mechanism of thermal degradation of main components of all samples was nth order reaction. Finally, a model based on three parallel reactions (for three pseudocomponents) that fit to nth order reactions was evaluated. This model was appropriate to predict the pyrolysis behavior of the raw and lead-polluted samples in all pyrolysis conditions studied., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The olive tree pruning is a specific agroindustrial waste that can be successfully used as adsorbent, to remove Pb(II) from contaminated wastewater. Its final incineration has been studied in a thermobalance and in a laboratory flow reactor. The study aims at evaluating the fate of Pb during combustion, at two different scales of investigation. The flow reactor can treat samples approximately 10(2) larger than the conventional TGA. A detailed characterization of the raw and Pb(II)-loaded waste, before and after combustion is presented, including analysis of gas and solids products. The Pb(II)-loaded olive tree pruning has been prepared by a previous biosorption step in a lead solution, reaching a concentration of lead of 2.3 wt%. Several characterizations of the ashes and the mass balances proved that after the combustion, all the lead presents in the waste remained in ashes. Combustion in a flow reactor produced results consistent with those obtained in the thermobalance. It is thus confirmed that the combustion of Pb(II)-loaded olive tree pruning is a viable option to use it after the biosorption process. The Pb contained in the solid remained in the ashes, preventing possible environmental hazards., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Batch isotherm studies were carried out on a laboratory scale: (i) to investigate the effectiveness to remove lead of two wastes (olive stone (OS) and olive tree pruning (OTP)), untreated and chemically treated; and (ii) to examine the applicability of various adsorption isotherms to fit the experimental data. Results from tests were analyzed using seven equilibrium isotherm correlations (Langmuir, Freundlich, Dubinin-Radushkevich, Temkin, Redlich-Peterson, Sips, and Toth equations). The sum of the squares of the errors was determined for each isotherm and the Langmuir equation provided the best fit. Chemical treatments increased the biosorption properties of these materials. The maximum biosorption capacities were: 6.33, 49.13, 14.83, and 38.93 mg g(-1) for untreated OS, HNO3-OS, H2SO4-OS, and NaOH-OS, respectively, and 26.72, 86.40, 72.78, and 123.80 mg g(-1) for untreated OTP, HNO3-OTP, H2SO4-OTP, and NaOH-OTP, respectively. Finally, the loss of mass for each waste (13.9, 14.3, and 36.8% for HNO3-OS, H2SO4-OS, and NaOH-OS and 35.1, 27.5, and 46.7% for HNO3-OTP, H2SO4-OTP, and NaOH-OTP, respectively) was taken into account and an effectiveness coefficient was determined for each adsorbent material.

Abstract: Biosorption of Pb(II) by olive tree pruning (OTP) treated with three chemical agents (HNO3, H2SO4 and NaOH) using a batch system was studied. The effect of pH over a range from 3.0 to 5.0, the initial lead concentration over a range from 50 to 250 g m−3 and the treatment concentration over a range from 100 to 2000 mol m−3 on the metal removal was investigated. All treatments improved the percentage of lead removal by native OTP. Improvements obtained with treatments of treated OTP respect to untreated OTP at pH 5, an initial lead concentration of 250 g m−3 and treatment at 1000 mol m−3 were 64.72, 55.05 and 64.82% to HNO3, H2SO4 and NaOH respectively. The metal uptake also increased by increasing the pH and the initial lead concentration. A 33 factorial experimental design was employed to study the effect of three factors (pH, initial lead concentration and treatment concentration) for olive tree pruning treated with three treatment (HNO3, H2SO4 and NaOH) and at three levels (low, intermediate and high). A second-order polynomial regression model was used to fit experimental data obtained, and results showed a good agreement with experimental data for the three cases studied. Results obtained for the three treatments were compared and the best response was obtained with OTP treated with NaOH. Optimization process predicted the optimum conditions for the maximum biosorption capacity of Pb(II) for each treatment: 25.54, 23.87 and 26.63 g kg−1 for treatments with HNO3, H2SO4 and NaOH respectively. The equilibrium data for biosorption of lead onto olive tree pruning were represented by the Langmuir and Freundlich isotherms, giving the best fit the Langmuir model. [Copyright &y& Elsevier]

Abstract: In this study, the effect of Pb(II) in biosorption of Cu(II) by almond shell from a binary metal mixture was studied and compared with the single metal ion situation in a batch stirred system and in a continuous system. It was observed that copper biosorption yields and copper equilibrium uptakes were slightly reduced by the presence of lead. This antagonistic action can be related with competition phenomena between metal cations in solution for active sites presented on almond shell. The affinity of Pb(II) for almond shell was higher than that of Cu(II). In binary systems in a batch stirred system, extended Langmuir model and extended Sips model were used to fitting experimental data. Biosorption equilibrium data fitted very well to both models in the concentration range studied. But, although differences between the fitting of these two models were insignificant, it was obtained that extended Sips model reproduced better the experimental results than the Langmuir one. The maximum biosorption capacities obtained for Cu(II) and Pb(II) were approximately 9.0mg/g and 13.7mg/g, respectively, Finally, breakthrough curves for continuous removal of Cu(II) from single and binary metal solutions were reported. Column competitive biosorption data were evaluated in terms of the biosorption (equilibrium) capacity of the column, the amount of metal loading on almond shell surface, the total biosorption yield, breakthrough and exhausted time. [Copyright &y& Elsevier]

Solid waste from olive oil production, the two-phase olive mill solid (OMS), was investigated for the removal of Pb(II) from aqueous solutions. This work focuses mainly on the kinetics of biosorption. The sorption kinetics was experimentally measured using stirred-batch systems under different initial concentrations and at varying solution temperatures. The pseudo-nth order kinetic model, pseudofirst-order kinetic model, pseudosecond-order kinetic model, and the Elovich equation were used to represent the kinetic data. The pseudosecond-order equation fitted the dynamic data very well under all the operating conditions. A contact time of approximately 60 min was required to reach the equilibrium. The results obtained for the effect of initial concentration on lead uptake by OMS showed that the equilibrium sorption capacity and the initial sorption rate increase as the initial metal concentration increases, while the kinetic constant of the process decreases. The effect of temperature on kinetic parameter values is less significant than the effect of lead concentration although a decrease on kinetic constant and initial sorption rate is produced as temperature rises, mainly at lower lead concentrations. Finally, the apparent activation energy of sorption was determined as −18.62 kJ·mol–1for an initial lead concentration of 10 mg·L–1. The negative value of activation energy showed that the Pb(II) adsorption process by OMS may involve a nonactivated chemical adsorption or a physical adsorption. [ABSTRACT FROM AUTHOR]

Abstract: This study examined the lead biosorption capacities of two solid wastes from olive-oil production, two-phase olive mill solid (OMS) and olive stone (OS), using batch experiments at different temperatures. The aim was to determine the isotherms of these wastes and thus their applicability as alternative biosorbents for lead removal. In addition, the solids were characterised by Fourier Transform Infrared (FTIR) spectroscopy. The OS sorption isotherms were characterised as type I. However, a step characteristic of type IV isotherms was observed in the OMS lead ion sorption isotherms. Well-known non-linear isotherm models, such as Langmuir, Freundlich and Sips, were tested for fit to the OS experimental data, whereas a two-step Langmuir-type model and an adaptation of the Dubinin–Astakov model that can mathematically describe multistep-shaped isotherms were used for the OMS data. The maximum lead uptake was 6.57mg/g for OS and 23.69mg/g for OMS at 25°C. The FTIR spectra before and after lead biosorption, confirmed that carboxyl groups were the main sorption sites for lead removal on the surface of both biosorbents. [Copyright &y& Elsevier]

The influence of the presence of Cr (III) on the biosorption of Pb (II) by three olive wastes (olive stone, the two-phase olive mill solid, and olive tree pruning) was investigated in a batch system in terms of equilibrium isotherm and adsorption yield. The results show that the three olive wastes have greater affinity for lead than for chromium and the best results are achieved at pH=5. The presence of chromium in the solution reduces the percentage of lead removal suggesting that there is a competition between the two metals for the binding sites, and that the biosorbent retains both species presenting more affinity for lead. Simultaneous biosorption phenomena of Pb (II) and Cr (III) on the three solid wastes were expressed by multicomponent isotherms. The extended Freundlich-type and Sips-type models were found to exhibit good fit to the experimental data for olive stone and olive tree pruning, respectively. [ABSTRACT FROM AUTHOR]

The article discusses research that examined the use of olive stone as an inexpensive biosorbent that will remove cadmium, chromium, and lead from aqueous solutions in a batch system as a function of pH, contact time, and temperature. Biosorption kinetics using the pseudo-second-order kinetic model was used to test experimental data, providing information on the biosorption processes of the three metal ions. The activation energy was determined and revealed that biosorption was taking place mainly through physical interactions. The Sips isotherm model was used to calculate the thermodynamic parameters.

In this work, the pyrolysis of post-consumer mixed plastic waste (polypropylene (PP), polystyrene (PS) and polyethylene film (PE)) is carried out. The solid product of the pyrolysis is characterized and tested for its use as adsorbent of lead present in aqueous media. The pyrolysis temperature has a great influence on the solid product yield, decreasing when the temperature increases. The highest yield to solid product obtained is from the pyrolysis of film at lower temperature (450 °C), reaching almost 14%. The results of product solid characterization reveal that the carbon, hydrogen and nitrogen content decreases with increasing pyrolysis temperature. Furthermore, both the ash and the volatile content are related to the pyrolysis temperature. The ash content is higher when the pyrolysis temperature is higher, while when the temperature increases, a solid product with lower volatile content is obtained. In respect to specific surface area, a higher pyrolysis temperature improves the properties of the solid product as an adsorbent. The adsorption capacity increases as the pyrolysis temperature increases, with the highest value of 7.91 mg/g for the solid obtained in the pyrolysis at 550 °C. In addition, adsorption capacity increases as the initial concentration of lead rises, reaching a maximum value close to 26 mg/g for an initial concentration of 40 mg/L. The Sips model is the one that best reproduces the experimental results of the adsorption process equilibrium study. [ABSTRACT FROM AUTHOR]

• Isolation of chemical constituents of almond shell was completed. • Study of thermal decomposition different fractions of almond shell was performed. • A kinetic model for describing thermal decomposition of almond shell was proposed. • The experimental and calculated data were in good agreement. • The effect of various heavy metal loaded by biosorption was analyzed. This research aims to provide a better knowledge of the thermal decomposition of almond shell and this material loaded with heavy metals in a previous stage of biosorption (cadmium, copper, chromium, nickel and lead). Firstly, isolation of constituents of the almond shell was carried out. According to chemical analysis almond shell was constituted of an 8.2% of moisture; 1.6% of hot water soluble compounds; 0.34% of ethanol soluble compounds; 50.8% of extract-free lignin; and 49.2% of extract-free holocellulose. Then, experiments were performed by thermogravimetric analysis (TGA) and differential thermogravimetry (DTG) under inert and air atmosphere at a heating rate of 15 K/min for each isolated fraction. After that, adequate reactions schemes were proposed to find kinetic parameters. Independent reactions were formulated for each constituent and kinetic parameters were obtained for each isolated material in a sequential procedure. Finally, the validation of the proposed schemes was verified by the goodness of fitting between experimental and simulated TG and DTG curves. It was observed that cadmium, copper, chromium, nickel and lead present in metal-loaded almond shell did not modify significantly the values of kinetic parameters which describe the thermal decomposition processes. [ABSTRACT FROM AUTHOR]

In the present work, biosorption of copper(II) in the presence of lead(II) ions by native pine cone shell (PCS) was investigated in batch and packed bed reactors. Particularly, it provides new information regarding binary biosorption of metals in continuous flow. The behavior of competitive Cu(II) and Pb(II) biosorption in batch was successfully described by the multicomponent Sips model, obtaining maximum capacities for Cu(II) and Pb(II) of 6.52 mg/g and 17.41 mg/g, respectively. The single-metal biosorption uptake capacities of the biomass for copper and lead were slightly inhibited by the presence of lead and copper, respectively. Pine cone shell removed the target metal ions in the affinity order of Pb(II) > Cu(II) quantified in mass basis. Factors such as covalent index of the metal ions may contribute to this result. In tests carried out in a packed-bed column, the biosorption capacity for Pb(II) (17.85 mg/g) was also higher than copper one (9.38 mg/g), confirming the higher selectivity of the pine cone shell for lead over copper ions in continuous system too. Finally, desorption studies indicated that Cu,Pb-loaded PCS could be easily eluted by 0.3 M HCl. [ABSTRACT FROM AUTHOR]

This work studies the complete use of untreated and chemically treated olive stone: first, it is applied as biosorbent of lead and later, reused as fuel in a pyrolysis process. The waste was chemically treated with three chemical agents to increase its biosorption capacity. Results from characterization show that the treatment of the OS has sound effects (higher surface area, lower carbon content, lower ashes content, higher calorific value, etc.). These results have important implications on the potential for a productive reuse of these waste materials, since their properties (as biosorbent and as fuel) improve significantly. For the complete use of the waste, the best chemically treated olive stone was chosen to analyze the biosorption–desorption cycles to remove lead from wastewater, obtaining a life factor of nine cycles. After the last cycle, its behavior on pyrolysis process was studied by dynamic thermogravimetry and derivate thermogravimetry. Results show that the thermal decomposition in an inert atmosphere can be modeled by separate decomposition of each of the three fractions which constitute the material. [ABSTRACT FROM AUTHOR]

Highlights: [•] Olive tree pruning was used as precursor for the development of new biosorbents for lead ions removal. [•] A description of kinetics of lead biosorption onto these new biosorbents was presented. [•] Kinetic data were successfully described with pseudo-nth order and double exponential models. [•] Lead biosorption properties of olive tree pruning were improved with treatments. [Copyright &y& Elsevier]

Abstract: Olive stone (OS), two-phase olive mill solid (OMS) and also olive tree pruning waste (OTP), three wastes of the olive-oil production, were tested as low-cost adsorbents for Pb (II) removal from aqueous solutions. In order to reduce the total number of experiments to achieve the best conditions of the batch biosorption procedure, two 32 factorial designs of experiments were carried out for each biosorbent. The factors considered were biosorbent dosage, pH, initial lead concentration and temperature. Three levels for each factor were used; biosorbent dosage (2g/L; 10g/L and 22g/L), pH (4; 5 and 6), initial lead concentration (10mg/L; 40mg/L and 70mg/L) and temperature (25°C; 40°C and 60°C). Two responses, the lead removal percentage and biosorption capacity after 120min of contact time, were then analyzed statistically using the Statgraphics Plus 5.1 software. A second-order quadratic model suggested the optimum conditions. Three dimensional plots demonstrated relationships between the lead ion uptake with the paired factors, describing the behaviour of biosorption system in a batch process. [Copyright &y& Elsevier]

Abstract: A new biosorbent for removing lead(II) ions from aqueous solutions has been investigated. This new adsorbent is olive tree pruning waste, an agricultural by-product in the Mediterranean region. Removal of lead(II) was studied at pH 5 in a batch system. The pseudo-first-order, pseudo-second-order and Weber and Morris kinetic models were applied to test the kinetic experimental data. The pseudo-second-order kinetic model provided the best correlation of the experimental data, indicating that sorption may be the rate limiting step for lead(II) biosorption by olive tree pruning waste. Equilibrium experimental results were fitted to Langmuir, Freundlich and Sips model isotherms to obtain the characteristic parameters of each model. The Langmuir and Sips isotherms best represented the measured biosorption data. According to an evaluation using the Sips equation, the maximum lead(II) biosorption capacities of olive tree pruning wastes were 26.24, 33.39 and 32.15mg/g at 25, 40 and 60°C. Using thermodynamic equilibrium coefficients obtained at different temperatures, various thermodynamic parameters, such as ΔG°, ΔH° and ΔS°, were calculated. The thermodynamics of the investigated lead ion–olive tree pruning system indicate a spontaneous and exothermic process. [Copyright &y& Elsevier]