Search

The main objective of this work was to assess the performance of combined processes, adsorption/ photodegradation of the ciprofloxacin antibiotic (CIP). Adsorption was achieved on natural hydroxyapatite (nat-HA) in the batch mode. The effect of pH (3–12), initial ciprofloxacin concentration (C0, 25–200 mg L−1), adsorbent dose (m, 0.25–3 g L−1), and temperature (T, 298–328 K) on the ciprofloxacin adsorption capacity was studied. At 298 K, the maximum uptake of 147.7 mg g−1 was observed with pH close to 8, 1 g L−1nat-HA dose, and 150 mg L−1 initial CIP concentration. Adsorption was effective, with a removal percentage of 82% within 90 minutes of contact time. For ciprofloxacin adsorption onto nat-HA, a pseudo-second-order kinetic model is well-suited. The Langmuir isotherm model successfully fit the experimental data and the process was spontaneous and exothermic. The coupling processes (adsorption/photocatalysis) were examined and found to be highly effective. For the remaining concentrations, the maximum degradation efficiency and mineralization yield were ~100% and 98.5%, respectively, for 1 mg L−1 initial CIP. The combination of the strong adsorption capacity of natural hydroxyapatite and the high photocatalytic activity of TiO2 can be an effective technique for removing fluoroquinolone antibiotics from wastewater.

International audience; Consideration is now being given to the use of metal coagulants to remove turbidity from drinking water and wastewater. Concerns about the long-term impact of non-biodegradable sludge on human health and the potential contamination of aquatic systems are gaining popularity. Recently, alternative biocoagulants have been suggested to address these concerns. In this study, using a 1 M sodium chloride (NaCl) solution, the active coagulating agent was extracted from Pinus halepensis Mill. Seed, and used for the first time to remove Congo red dye, the influence of numerous factors on dye removal was evaluated in order to make comparisons with conventional coagulants. The application of biocoagulant was shown to be very successful, with coagulant dosages ranging from 3 to 12 mL L(-1) achieving up to 80% dye removal and yielding 28 mL L(-1) of sludge. It was also found that biocoagulant is extremely pH sensitive with an optimum operating pH of 3. Ferric chloride, on the other hand, achieved similar removal rate with higher sludge production (46 mL L(-1)) under the same conditions. A Fourier Transform Infrared Spectroscopy and proximate composition analysis were undertaken to determine qualitatively the potential active coagulant ingredient in the seeds and suggested the involvement of proteins in the coagulation-flocculation mechanism. The evaluation criteria of the Support vector machine_Gray wolf optimizer model in terms of statistical coefficients and errors reveals quite interesting results and demonstrates the performance of the model, with statistical coefficients close to 1 (R = 0.9998, R(2) = 0.9995 and R(2) adj = 0.9995) and minimal statistical errors (RMSE = 0.5813, MSE = 0.3379, EPM = 0 0.9808, ESP = 0.9677 and MAE = 0.2382). The study findings demonstrate that Pinus halepensis Mill. Seed extract might be a novel, environmentally friendly, and easily available coagulant for water and wastewater treatment.

Published in Industrial & Engineering Chemistry Research. https://doi.org/10.1021/acs.iecr.2c03799

The Radke-Prausnitz model, a typical three-parameter model belonging to the Langmuir-Freundlich-type equation, is increasingly being used to correlate the equilibrium data of various adsorption processes. However, very few published works provide the correct information on (1) the nonlinear form of this model, (2) the units of its parameters, and (3) its original citation. This work provides a critical analysis of the Radke-Prausnitz model with special emphasis on promoting its proper application in adsorption research. The correct expression and citation of the models used in adsorption studies are provided. The correct units of its parameters aRP, bRP, and β are L/kg, (mol/kg)/(mol/L)β, and unitless when the solution phase concentration Ce is given in mol/L and the adsorbed phase concentration qe is defined in mol/kg. The Radke-Prausnitz model can be reduced to the Henry, Freundlich, Langmuir, or Redlich-Peterson model in some special cases. The Radke - Prausnitz model is valid when the exponent β is in the range of 0≤β≤1. A new adsorption equilibrium constant of this model is introduced. The feasibility of using the new equilibrium constant to calculate the thermodynamic parameters (ΔG°, ΔH°, and ΔS°) of adsorption processes is discussed herein.

International audience; Water contaminated by methylene blue (MB) dye was treated with activated carbon based on locally collected jujube stones. This activated carbon was characterized by physico-chemical methods after preparation and chemical activation. Response surface methodology (RSM) was used to maximize the MB uptake a dependent variable in Box-Behnken Design (BBD) with the initial concentration of methylene blue (400-700 mg/L), adsorbent dosage (0.6-1.6 g/L), contact time (30-540 min), pH (7-11) and temperature (20-50 degrees C) as inde-pendent variables. Then, the database created by BBD was further modeled using Gaussian Process Regression coupled with Bagging (Bootstrap Aggregation_Bag) and Dragonfly optimization algorithm (GPR_DA_Bootstrap). The results of the optimization analysis using the GPR_DA_Bootstrap model are shown to be superior to those of the BBD model. The experimental validation of the optimal conditions of the GPR_DA_Bootstrap model (X1 = 700 mg/L, X2 = 0.6 g/L, X3 = 540 min, X4 = 11, and X5 =50 degrees C) led to an MB uptake (501.01 mg/g) significantly higher than that of BBD (456.00 g/g). In addition, the very low error between the experimental and the predicted values given by the GPR_DA_Bootstrap model (8.64 mg/g) compared to that of the BBD model (22.19 mg/g), should be highlighted. This clearly shows the efficiency and the performance of the GPR_DA_Bootstrap model on the one hand; as well as the effectiveness of activated carbon prepared from jujube stones (PJAC) as a low-cost adsorbent on the other hand.

The study mentioned in the title of this comment paper contains some calculations/results that disagree with some basic chemistry concepts.

Published in Chemical Engineering Science. Free Download (beforeOctober 16, 2022):https://authors.elsevier.com/c/1ff2G26dbwuNE

Published in Separation and Purification Technology. Free download:https://authors.elsevier.com/a/1ghmT4wbrTBXso

Experimental equilibrium data for the adsorption of water contaminants on solid surfaces are generally correlated using suitable isotherm expressions. In most cases, adsorption isotherms are used empirically with the primary aim of finding the best fitting ones. The literature of adsorptive water decontamination is replete with such isotherm comparisons, usually evaluated on the basis of some statistical metrics such as R2 and RMSE. For example, several studies have compared and ranked the isotherm equations of Hill, Sips, Koble–Corrigan, and Liu. These comparative evaluations imply that the four isotherms possess different data fitting abilities, and consequently it is possible to identify the most accurate one. The present study argues that this commonly held notion is incorrect. It demonstrates that the four isotherms provide the same results when fitted to three previously published data sets. This finding suggests that the four isotherms are mathematically equivalent despite apparent differences in their formulations. Indeed, a mathematical analysis unequivocally shows that the Hill, Sips, Koble–Corrigan, and Liu isotherms can be represented by a single generic equation with three arbitrary fitting parameters. As such, the four isotherms must provide exactly the same fit to a given set of isotherm data.

In this discussion, we highlight that the terms sorption and adsorption are often confused and misused in many articles. Even if one thought their formal definition is well known, this does not appear to be the case.We recommend encouragement to adopt the word adsorption only when fully supported by appropriate data and using the sorption terminology when it is morespeculative, typically in complex solid/fluid natural systems.

Two flaws in concepts were identified and discussed in the paper ("Removal of Pb(II) from contaminated waters using cellulose sulfate/chitosan aerogel: Equilibrium, kinetics, and thermodynamic studies". J. Environ. Manag. 286, 112167; https://doi.org/10.1016/j.jenvman.2021.112167). In the literature, the Radke-Prausnitz model is expressed in different forms, but some of them are incorrect. The first flaw is related to the nonlinear form of the Radke-Prausnitz model. The nonlinear form of this three parameters model is expressed correctly as [Formula: see text] . The units of two parameters are A

The present work examines the influence of the leaching conditions on the release of various chemical elements from a cementitious material obtained by solidification of an industrial waste rejection of Algeria. Toxicity Characteristic Leaching Procedure (TCLP), X-ray diffraction (XRD) and Scanning electron microscopy coupled with energy dispersive X-ray microanalysis SEM-EDX analyses were employed to characterize the waste and the stabilized/solidified materials. Than several formulations were prepared with different percent of waste ranging from 0 % to 30 %. To evaluate the influence of leaching conditions on the release of chemical ions (Zn2+, Pb2+, Cl-, Mg2+, Ca2+, Na+, K+ and SO42−) contained in the stabilized and solidified materials, the Acid Neutralization Capacity (ANC), the Pore Water (PW) and Monolith Leaching Tests (MLT) have been carried out. The leaching tests (ANC, PW and MLT) have shown a low metal leachability. However, the lowest released amount was observed for the MLT.

The study mentioned in the title of this comment paper contains some calculations/results that disagree with some basic chemistry concepts. These misleading calculations include (i) both kinetic and isotherm modelling through linear equations, and (ii) calculating the thermodynamic parameters for the adsorption processes. Thus, we run through the correct way to make these calculations. In our opinion, it is very confusing to continue to disseminate erroneous methods as applied in the original paper.

The objective of this work is to use stabilization/solidification (S/S) on the landfill leachates that often are heavily polluted by heavy metals and require proper treatment before discharge into the environment. The process consists of a S/S using a hydraulic binder in order to limit the solubility and mobility of the pollutants. While cement is the most used binder based on S/S values, in this study we substituted it by cement kiln dust (CKD) in two replacement ratios 25.50 and 100 %. The resulting effect on mechanical resistance and on retention of pollutants was evaluated. A metal (lead, iron and zinc) contaminated leachate from the landfill site of Sidi-Bouderham in Algeria was mixed with an amount of cement and cement kiln dust in different proportions in order to optimize our formulations. The smooth paste was obtained and a standardized test of the test specimens was analyzed for mechanical resistance after 7 and 28 d of setting. Our results show that F1P (100 % Cement) and F2P (75 % Cement + 25 % CKD) point on satisfactory mechanical strength and metal retention capacity. Our approach suggests a promising approach for remediation of polluted sites.

The use of synthetic hydroxyapatites (HAps) in biomedical and environmental applications is well warranted given that they have been shown to behave as an excellent bio-compatible material in human teeth and bones. In this paper, a series of HAps doped and co-doped with two metal cations (zinc and magnesium) has been successfully synthesized by means of the precipitation method using CaCl

A local bentonite clay from Maghnia (Algeria) was activated with chemical method characterized and tested for its ability to adsorb Zinc (II) from refinery wastewater. Batch experiments were conducted to study the effects of the main parameters such as contact time, initial metal concentration and agitation speed on the adsorption of Zn (II) by local bentonite clay. Experiences have led to the following results: an adsorption rate of the order of 98 % with operating conditions of pH = 4.5, agitation speed of 400 rpm and temperature of 25 ºC. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to analyze the kinetic data obtained at different concentrations. The pseudo-second-order kinetic model agrees very well with the experimental results. In order to determine the best-fit isotherm, in the studied concentration range of Zn(II) at 25 ºC, the experimental equilibrium data were analyzed using tow adsorption isotherm models: Langmuir and Freundlich models, these two models give a good fit.

To the Editor:Recently, the above-named paper (hereafter named as ‘the original paper’) was published in this journal by Tan and Sen.[1] But even though the objective of the paper pretends to be am...

Adsorption thermodynamics is an integral part of the study of adsorption and plays a vital role in estimating adsorption mechanism (i.e., physisorption and chemisorption). For the liquid-phase adsorption, the equilibrium constant of some adsorption isotherm models (Langmuir, modified Langmuir, Langmuir–Freundlich, modified Langmuir–Freundlich, Liu, Khan, Sips, Hill, Toth, Redlich–Peterson, Koble–Corrigan, and Radke–Prausnitz models) and the constant of Henry and Freundlich models have been directly or indirectly applied for calculating the corresponding thermodynamic parameters (∆G°, ∆H°, and ∆S°). This study explored the effects of the selection of (1) the unit of adsorption isotherm (qe vs. Ce), (2) the equilibrium constant of adsorption isotherm model, and (3) the linear and nonlinear forms of the van’t Hoff equation on the value (sign and magnitude) of the thermodynamic parameters. A commercial activated carbon was selected as a typical adsorbent to adsorb methylene green dye (target adsorbate) in solution. Results indicated that the constants of the Henry and Freundlich models could not be applied for calculating the thermodynamic parameters. The equilibrium constants of the modified Langmuir and modified Langmuir–Freundlich models are not suitable for calculating the thermodynamic parameters in this study compared to the other equilibrium constants of the Langmuir, Langmuir–Freundlich, Khan, Liu, Sips, Redlich–Peterson, Toth, Hill, Radke–Prausnitz, and Koble–Corrigan models. The thermodynamic parameters were calculated from thermodynamic equilibrium constant derived from the constant of the Redlich–Peterson model or the Radke–Prausnitz model (the van’t Hoff equation: adj-R2 = 0.9999).

International audience; In many industrial sites, a series of various organic and inorganic co-contaminant species are simultaneously present in their aqueous discharges. This therefore justifies the recent interest and the choice of binary and ternary adsorption of three co-contaminant species to understand their competitive effects. Here we introduced two types of theoretical adsorption models, recently developed by us: multi-logistic distribution and statistical physics. These modeling approaches were applied in order to understand the adsorption of two cationic dyes (Rhodamine B, RB and Malachite Green, MG) and one metal cation (Cadmium Cd(II)) on granulated activated carbon (GAC). New experimental batch adsorption data were obtained with these mono-component, binary and ternary systems. The adsorption capacities of all these pollutants decreased from single to binary and ternary systems. Moreover, although Cd(II) did not lead to any notable competitive effect, when the two dyes were simultaneously present (binary and ternary systems) there was an increase in the adsorption capacity for RB and a decrease for MG, thus indicating a complex removal process due to different adsorption effects. Both models were used to calculate affinities, dissociation constants, steric and energetic parameters to characterize the single, binary, and ternary adsorption of tested pollutants. Modeling results indicated that the number of captured adsorbates per active receptor site of GAC decreased from single to binary and ternary systems, signaling a competitive effect for the same adsorption site. Based on this parameter, the adsorption orientation of these three pollutants was described. Interestingly, the models provided adsorption energies which allowed the characterization of the interactions between the adsorbates and the adsorbent surface. Calculated adsorption energies showed that the adsorption in single, binary, and ternary systems was associated to physisorption.

There have been numerous environmental geochemistry studies using chemical, geological, ecological, and toxicological methods but each of these fields requires more subject specialist rigour than has generally been applied so far. Field-specific terminology has been misused and the resulting interpretations rendered inaccurate. In this paper, we propose a series of suggestions, based on our experience as teachers, researchers, reviewers, and editorial board members, to help authors to avoid pitfalls. Many scientific inaccuracies continue to be unchecked and are repeatedly republished by the scientific community. These recommendations should help our colleagues and editorial board members, as well as reviewers, to avoid the numerous inaccuracies and misconceptions currently in circulation and establish a trend towards greater rigour in scientific writing.

International audience; We make use of chemical activation with phosphoric acid to prepare an activated carbon from date stones (DSAC). After characterization for surface area and pore volume, it was tested as an adsorbent for gallic acid (GA) removal from aqueous solutions Operating variables including contact time (410 min), adsorbent dosage (0.1 g in 150 mL), GA concentration (10 mg/L) and solution pH (4.5) were optimized using the Box-Behnken design (BBD) under response surface methodology (RSM) approach. Adsorption of GA onto DSAC may be described by the pseudo-second-order kinetics model equation suggesting that the process is chemisorption. The equilibrium data fitted the Langmuir isotherm model with a maximum capacity of 156 mg/g (25?C, pH 4.5). The GA adsorption process was found to be exothermic, while ?G? was negative implying that the reaction is spontaneous.

International audience

Sorption of Cr(III) and Cr(VI) ions onto 2% grape stalk (GS) powder entrapped in a biopolymeric gel matrix of calcium alginate (CA) has been investigated and a mechanism for the retention of both, Cr(VI) and Cr(III) is proposed. Protons were found to be consumed in Cr(VI) sorption/reduction and to compete with Cr(III) for the sorbent active sites. Isotherm equilibrium was modelled according to Langmuir equation: maximum capacity was found to be 6.4 and 3.6 mg g −1 for Cr(III) and Cr(VI), respectively. The important Ca 2+ release observed when Cr(III) is sorbed indicates that ion exchange is the main mechanism involved at concentrations lower than 200 mg L −1 while other mechanisms such as microprecipitation or coordination might take place for higher initial concentrations. In the case of Cr(VI), the sorption mechanism is based on the reduction to Cr(III) promoted by both protons and the functional groups on the GS surface; this reduction-formed Cr(III) is retained by the alginate gel matrix and by microprecipitation onto the surface of GS particles. ESR and SEM-EDX were used to identify chromium species sorbed on the solid phase. Results from this study suggest that GS entrapped in CA gel beads is an effective sorbent for both, Cr(III) and Cr(VI) removal from aqueous solutions.

International audience; Removal of Methylene Blue (MB) from aqueous solutions is studied using a raw Algerian kaolin sample as a low-cost adsorbent. The effects of pH, contact time, dye concentration and temperature are all taken into consideration. The adsorption kinetics results are adjusted to best fit the pseudo-second order model. The experimental data are analyzed by Langmuir isotherms, revealing that the maximum adsorption capacity of MB on this kaolin sample equals 52.76 mg/g at T = 25 °C and pH = 6.0. The calculated thermodynamic data demonstrates that adsorption is spontaneous and enhanced at higher temperatures. Desorption studies with water indicate that the adsorbent could successfully retain MB, even after four cycles. From these results, it can be considered that the raw Algerian kaolin sample tested herein is effective in the removal of MB from aqueous solutions and moreover may be used as an alternative to high-cost commercial adsorbents. © 2017 Elsevier B.V.

Letter to the Editor; International audience; Due to our experience of reviewing scientific papers for a number of environmental journals,we strongly suggest removal of “heavy metals” from all future key-words lists, and replacement in the title, abstract, and full text of every newly submitted paper with words like “potentially toxic metal(s)/element(s)” or “trace metal(s)/element(s)”, according to the context.

International audience; The chemical associations of Cd, Cu, Pb, and Zn in four mine soil samples from the Amizour-Bejaia Pb/Zn mine (Algeria) have been investigated by a five-step sequential extraction procedure. Although Cd preferentially binds to carbonates, Cu, Pb, and Zn are mainly associated with the organic and reducible fractions. Batch adsorption experiments with either mono- or multi-metallic solutions are described with the Freundlich isotherm model. Whatever the nature of the soil sample, the sorption behavior for each given metal except Pb is very similar, indicating that the binding sites at the soil surface are progressively occupied by the metal from the solution. On each soil sample, the decreasing order of sorption can be established as Pb >> Cu > Cd > Zn. When the four metals are simultaneously applied to each soil sample, their specific behavior is strongly affected by their interactions and/or competition for the available surface sites: we generally observed isotherm curves with a slight maximum before the plateau at higher solution concentration. Although Cu is only slightly affected by the other metals, in the case of Pb, Cd, and Zn, the sorbed amounts strongly decreased. © 2017, Saudi Society for Geosciences.

International audience; We determined the acidity constants of tebuconazole and penconazole, two fungicides from the group of 1,2,4-triazoles. Potentiometric titrations were performed in a 20 % (v/v) acetonitrile/water mixture at 25 °C and at a fixed ionic strength (KNO3, 0.1 mol*dm−3). The pKa values (representing thermodynamic constants) were determined to be 5.0 ± 0.1 and 5.2 ± 0.1 for tebuconazole and penconazole, respectively. These values could be used in pure water solutions to consider the protonated or deprotonated forms when studying the field behavior of these fungicides. Molecular modeling calculations allowed identifying the N4 atom as the protonation site.

International audience; The column leaching behavior of lead and zinc is studied on a soil sample from the Amizour-Bejaia mining region, which is one of Algeria's largest natural reserves for Pb and Zn ores. The maximum amount of metal bound to the soil sample after column leaching by a mono-metal solution at pH 7 is 7.0 and 11.3 g/kg for Zn and Pb, respectively. These values exceed the maximum loading capacities derived from previous batch experiments conducted under similar conditions. The studied soil sample displays a stronger affinity for Pb than Zn under the study conditions. These two metals are associated with various chemical fractions of the mine soil sample, as revealed by a five-step, operationally-defined sequential chemical extraction procedure (with fractions categorized as: exchangeable, acid extractable, reducible, oxidizable, and residual) following column leaching. After metal addition and sorption, carbonates (i.e. the extractable fraction) and Fe- and/or Mn- (oxy)(hydr)oxide phases (reducible fraction) in the soil sample dominate for both Pb and Zn. The extractable fraction is mainly reserved for the purpose of zinc retention; moreover, the stabilization with Fe-Mn (oxy)(hydr)oxide phases serves as a major carrier for Pb.

International audience; ABSTRACT: The preparation of activated carbon from jujube stones with H2SO4 activation and its ability to remove lead from aqueous solutions were reported in this study. The surface structure of the activated carbon was characterized by various physico-chemical methods. Sorption studies were carried out by varying the initial metal ion and the pH: the amount of sorbed Pb(II) ions increased with increasing pH and initial Pb(II) ions concentration. The removal of lead ions was rapid and the kinetic of sorption can be well described by pseudo-second order modelling. The Langmuir model conveniently fits the data of isotherm experiments and the monolayer sorption capacity of Pb(II) ions was determined as 71.43 mg/g at pH 6.0 and 25°C. These results showed that activated carbon prepared from jujube stones could be considered for application as a potential sorbent for the removal of lead from wastewaters. © 2016 Taylor & Francis.

RP-HPLC measurements (in water + 60% v/v acetonitrile, on a porous polystyrene column) lead to a linear calibration between the retention factor logk and the lipophilicity logP for a series of 9 OECD standards. Introduction of a variable indicator D for hydrogen-bond donors enhances the goodness of fit. From experimental retention factors, estimated values of logP are given for 23 substituted (hetero)arylcarboxamides derived from 2-amino 4,6-dimethyl pyridine, whose anti-inflammatory behavior and anti-cholinesterase activity were previously characterized. From the logP versus logk relationship, a family-dependent indicator variable D is attributed to each compound.

International audience; A Mn-rich slag sample coming from a pyrometallurgical plant recycling alkaline batteries was submitted to environmental conditions during one year. After crushing, the slag was buried in topsoil and the leachate was periodically collected in order to monitor the leached amounts of metallic elements (ME). Results evidenced a low release of the slag constituents (Mn: < 0.01%). The SEM/EDS investigations did not show alteration features supposing a weak dissolution of the primary phases (tephroite, bustamite and leucite). The modification of the pH induced by the slag enhanced the mobility of soil components and of the organic matter, particularly in the vicinity of the soil/slag contact zone. This suggested that the slag indirectly influenced the ME mobility through the organic matter and colloidal transports. The comparison with a classical laboratory column test evidenced the underestimation of the leached amounts due to the differences of operational conditions.