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Abstract One of the main challenges of dyes adsorption technology application wide-spreading is the fate of the generated dyes-loaded-biomasses, which in certain cases could represent a serious threat to the environment. In this research work, an innovative and eco-friendly approach was established for the management of a lignocellulosic material (alkaline treated orange tree sawdust: ATOS) loaded with methylene blue (MB) at a concentration of 107 mg g−1. This approach consists first of all to a rapid and important MB desorption (more than 91%) from fixed bed depth columns by low cost saline solutions (NaCl: 0.5 M). The issued solutions contained high MB concentrations (>3400 mg L−1) permitting a partial recovery of the dye as a solid phase with a purity of 93% that could be reused again in the industrial process. The second step concerns the treatment of the remaining dissolved MB in the desorbed solutions through anodic oxidation process by using bipolar Si/BDD (Boron Doped Diamond) electrodes. The presence of chlorides anions in the desorbed solutions enhances considerably their discoloration and organic carbon removal efficiencies and kinetics and significantly reduces the related consumed energy. The quality of the resulting treated wastewaters allows its possible reuse in the industrial process. Finally, five consecutive adsorption/desorption cycles experiments showed that ATOS could be reused several times for the MB adsorption without significant efficiencies decrease. All these results confirm the validity of our strategy aiming to turn dyes-loaded-lignocellulosic-biomasses from pollution source to values. Graphical abstract Image 1 Highlights • Methylene blue desorption was studied in fixed bed column mode. • Methylene blue desorption was governed by an ion exchange mechanism. • Dye recovery was achieved with a high purity level of more than 92%. • Biomass ability for reuse was confirmed after five successive regeneration cycles. • High efficiency and low energy consumption when degrading MB by anodic oxidation. [ABSTRACT FROM AUTHOR]

Abstract: The present paper aims to study the effectiveness of an abundant marine waste named Posidonia oceanica (P. oceanica) on ammonium removal from aqueous solutions under different experimental conditions. The results of this study have shown that ammonium biosorption onto P. oceanica fibers increases with initial ammonium concentrations and pH increase. Biosorption isothermal data were well fitted by Langmuir model suggesting a monolayer and uniform adsorption process. The kinetic modeling of the experimental data indicated that they were well described by a pseudo-second-order model predicting a chemisorption process. The scanning electron microscopy (SEM), the energy dispersive spectroscopy (EDS) and the Fourier transform Infra-red spectroscopy (FTIR) analysis before and after biosorption of ammonium onto P. oceanica revealed that the main involved mechanisms are both surface ion exchange with magnesium and calcium cations and surface or intraparticle sharing between ammonium and functional groups, such as O–H, N–H, C=O and C–H stretching, and N–H bending. [Copyright &y& Elsevier]

Abstract: In the present study, the effects of temperature and pH on ammonium biosorption onto Posidonia oceanica fibers were investigated. The results showed that the ammonium biosorption onto these fibers occurred for a wide pH range and the adsorption capacity of these fibers increased with increasing temperature. The modeling studies showed that the ammonium biosorption was well described by the pseudo-second-order model, predicting therefore chemisorption interactions-type at earlier stages and intraparticle diffusion at later stages. The ammonium biosorption was governed by film diffusion process at various temperatures. Besides, equilibrium data were very well represented by Langmuir isotherm, which confirmed the mono-layer coverage. The use of P. oceanica fibers presents an interesting option for both tertiary wastewater treatment (as a possible non-conventional biosorbent for the removal of ammonium), and waste recycling (as a fertilizer and compost). [ABSTRACT FROM AUTHOR]

Abstract: Sawdust, an available and renewable biomass, was investigated as a novel ammonium biosorbent. Biosorption occurred over a pH range of 6–10, reached an equilibrium state within only 20min, and can be described by a pseudo-second-order model predicting a chemisorption process. Equilibrium data were very well represented by Langmuir isotherm and confirm monolayer coverage. FTIR analysis before and after biosorption of ammonium onto sawdust suggested that the main mechanisms involved in the removal of ammonium might be the ionic exchange and complexation. The use of sawdust presents an interesting option for both tertiary wastewater treatment (as a possible non-conventional biosorbent for the removal of ammonium), and waste recycling (as a fertilizer and compost). [Copyright &y& Elsevier]

Abstract: The hydraulic residence time (HRT) is a key parameter affecting the soil aquifer treatment process (SAT) efficiency as tertiary treatment of wastewater through infiltration in vadose zone. In order to maximize the HRT, a pulsed feeding technique of a salt solution (used as conservative tracer) was adopted to allow the increase of HRT and soil aeration between pulses. For this reason, several laboratory column experiments combined with the use of a numerical model was conducted. The optimal number of pulsations that meet with the maximum of the HRT and the temporal variation of the water saturation into the column was determined for different applied hydraulic heads. It varies between 10 and 12. The maximum corresponding water stock in the porous media column was evaluated to about 84%, 79% and 73%, respectively, for an applied hydraulic head of 96, 75 and 50 cm. The applied hydraulic head had an important effect on the HRT. In fact, this parameter varies from almost 6.5 to 10.8 h for an applied hydraulic head of 96 and 50 cm. The change in the permeability of the soil had also a significant effect on the HRT. Hence, HRT is decreased of about 9% when the soil permeability at saturation is multiplied by 2, and increases of about 11% when the permeability is two times lower. [Copyright &y& Elsevier]

Pyrolysis is a thermochemical process that permits the conversion of biomasses into energy (bio-oil and biogas) and a solid residue called biochar. The generation of biochar from lignocellulosic materials has been, for longtime, the predominant research focus. Wastewater treatment plants produce huge amounts of sludge biomass and there exists an increasing evidence for their possible reuse as a promising pyrolysis feedstock in recent literature. Though the valorization of biochars generated from lignocellulosic biomasses has been the subject of many reviews, there exists a critical knowledge gap regarding the effect of synthesis conditions of the sludge-derived biochars (SDBs) on their efficiency in the treatment of wastewater. This review critically analyzes the available literature related to SDBs characteristics and application to adsorb inorganic and organic pollutants from effluents. The physico-chemical properties and adsorption efficiency of SDBs are mainly tuned by the nature of raw sludge, pyrolysis conditions, and pre/post-treatments. Indeed, biochars originating from digested sludge have better adsorption capacities towards nutrients and heavy metals compared to those obtained from the non-digested sludge. The nutrients recovery from urban wastewater could be significantly improved when the raw sludge is mixed with lignocellulosic biomass and Mg/Ca rich materials. On the other hand, the chemical activation of sludge at reagent/sludge ratios higher than 2:1 permits to generate SDBs with adsorption capacities comparable and even better than commercial activated carbons. Moreover, the embedment/coating of SDBs with specific nanomaterials and tailored functional groups could significantly improve the adsorption capacities of various organic toxic pollutants and at the same time enhance their chemical degradation. The effect of the nature of target pollutants (organic or inorganic) on the underlying adsorption mechanisms by SDBs was also deeply reviewed. Finally, this paper provides the main application challenges as well as insights regarding the promising future directions for SDBs research and development. • This review evaluates the use of sludge-derived biochars for wastewater treatment. • Synthesis conditions influence the adsorption properties of SDBs. • Higher removal capacities of pollutants are obtained with activated SDBs. • Significant increases of removal capacities with nanocomposite-embedded SDBs. • Adsorption mechanisms are different for organic and inorganic pollutants. [ABSTRACT FROM AUTHOR]

In the present research, the optimization of the photocatalytic degradation of simulated textile effluent containing two pollutants (Methylene blue (MB) and Zinc) consisted of studying the variation of four parameters, namely initial MB concentration ([MB] I , mg/L), zinc concentration ([Zn 2+ ] I , mg/L), sodium chloride concentration ([NaCl] I , M) and flow rate (Q, mL/min) through a design of experiment using the response surface methodology approach. Results showed that MB degradation depends by order of importance on NaCl concentration > MB concentration > ionic zinc concentration > flowrate. Modeling results presented a good concordance between predicted and experimental values with acceptable correlation coefficients (R 2  = 0.9879 and R 2 (adjusted) = 0.9773). Desirability function was applied on the second-order polynomial equation to determine the optimal experimental condition for fastest total photocatalytic degradation and it was identified as follows: For a maximal target of 85.91% and a desirability of d = 1.0, [MB] = 75 mg/L, [Zn 2+ ] = 45 mg/L, [NaCl] = 0.125 M and Q = 500 mL/min. Moreover, results showed that zinc had a good affinity to cellulose material and contributed on enhancing the photocatalytic activity in terms of degradation. Mineralization of the dye was assessed for the optimal conditions using the TOC method. Moreover, special attention was also paid to better understand the effect of inorganic pollutant, scavenging effects of different molecules such as EDTA, isopropyl alcohol and CCl 4 were examined and discussed. [ABSTRACT FROM AUTHOR]

The goal of the present research is to study the effect of the inorganic species on the pyrolysis mechanism of lignocellulosic biomass. Many contradictions as the catalytic role of inorganic salts characterize the research works published up to now. These ambiguities are reasonably due to the morphological and structural modifications of the reacting biomass by the various demineralization and impregnation methods, that impact on the pyrolysis mechanism. In order to clarify the effect of inorganics on the pyrolysis mechanism, alkali and alkaline earth (AAEM) containing salts were deposited by impregnation method on cypress sawdust. Nuclear magnetic resonance analyses showed that the biomass structure was preserved and that metal deposition passes through a cationic exchange mechanism. The thermogravimetric analyses show that AAEMs have different effects by influencing the degradation behavior and the mass balances. In particular, potassium and sodium elements accelerated the hemicellulose thermal degradation without modifying the reaction mechanism. In addition, they showed a catalytic effect in the cellulose degradation towards low weight molecules decomposition and condensation reactions leading to the increase of the char yield. Contrary, the presence of magnesium and calcium seems to inhibit the hemicellulose thermal degradation without a significant effect on the cellulose degradation mechanism. [ABSTRACT FROM AUTHOR]

The purpose of the present research is to investigate the effect of background electrolytes on the phosphorus (P) sorption by four different natural clay samples (NCS): Jebel Tejera-Esghira (JTE) in Medenine area, Douiret (DR) in Tataouine area, Jebel Aidoudi (JA) and Zemlet El Beida (ZB) in Gabes area. The mineralogical and chemical characterization of the NCS showed that they are essentially composed of illite, kaolinite, smectite, with small fractions of quartz and calcite. The P sorption was investigated in batch mode in the presence of three different background electrolytes (CaCl 2 , NaCl and KCl with 99% of purity) under different experimental conditions of contact times (3 h), initial concentrations (25–150 mg.L−1), ionic strength (0–1 M), temperature (295–325 K) and pH (3–11). Experimental results indicated that P sorption in the presence of electrolytes is a rapid process since about 95% of P was observed within a contact time of 180mn. The highest P adsorption capacity was determined to 7.39 ± 0.65, 7.96 ± 0.82, 8.07 ± 0.55 and 8.83 ± 1.05 mg g1 for JTE, JA, ZB and DR. At equilibrium, the P adsorbed amount by the raw NCS was assessed to 7.75 ± 0.55, 8.34 ± 0.75, 8.8 ± 0.3 and 8.85 ± 0.75 mg g−1 for JTE, JA, ZB and DR. This amount increased by about 0.11, 0.08, 0.05%; 0.14, 0.06, 0.04%; 0.17, 0.1, 0.09 and 0.13, 0.11, 0.01% when adding the CaCl 2 , NaCl and KCl respectively. Moreover, the NCS capacity in removing increased with the increase of the initial P concentrations and the decrease of the liquid medium pH values. Also, P adsorption decreases with the increase of temperature. The P kinetic and isothermal removal experimental data were well fitted with the Pseudo-second order and Langmuir models respectively indicating that P adsorption onto NCS particles is mainly governed by chemical processes and occurs heterogeneously on multi-layers surfaces. • Sorption study on natural clay relevant to Tunisia repository program. • Sorption follows ion exchange at low pH and inner sphere complexation at high pH. • Smectite dominates the sorption behavior of natural clay. • Modeling of sorption data for phosphorus-natural clay–ground water system. • Isotherm data are well reproduced by the model at lower phosphorus ion concentration. [ABSTRACT FROM AUTHOR]

The olive oil industry is an important economic sector in Mediterranean countries. However, oil production is unfortunately accompanied by the generation of huge amounts of olive mill solid wastes (OMSW) and olive mill wastewater (OMWW). In the present study, a strategy is proposed for converting these olive mill wastes into biochar through pyrolysis, for their later use as an organic amendment in agriculture. Specifically, two biochars were prepared from the pyrolysis of OMSW at 500 °C, either alone or impregnated with OMWW (OMSW-B and I-OMSW-B). The characterization of the OMSW and I-OMSW samples and their derived biochars showed that the fixed carbon and ash contents in the feedstocks increased by 38% and 11% respectively for OMSW-B, and by 37% and 12% respectively for I-OMSW-B. Interestingly, the impregnation process significantly increased Na, P, K, Ca and Fe contents in the produced biochars. The effect of OMSW-B and I-OMSW-B amendments at different application dose (1%, 2.5% and 5% wt/wt) on the enzymatic activity of an agricultural soil was performed at laboratory scale with a pot test. The experimental results showed that phosphatase and urease activity increased with biochar application rate; amendment with I-OMSW-B at 1%, 2.5% and 5% enhanced the phosphatase activity by 63%, 142% and 285% and urease activity by 50%, 116% and 149%, respectively. On the other hand, dehydrogenase and protease activities were higher for the application rate of 2.5% biochar. Biochar amendment promoted tomatoes seedling growth after 10 weeks, which was highest in the application rates of 2.5% and 5% for both OMSW-B and I-OSMW-B. Thus, the produced biochars had great potential to be used as biofertilizers in agriculture. Unlabelled Image • Slow pyrolysis performed to convert OMSW and its impregnated form onto biochars • Biochars characterized using proximate, mineral analysis and crystalline structure • I-OMSW-B exhibited high contents of C, P and K comparing to initial feedstocks. • I-OMSW-B amendment promoted tomatoes seedling growth and enzymatic activities. • Studied biochars didn't have phytotoxic effect under tested doses. [ABSTRACT FROM AUTHOR]

Olive mill wastewater (OMW) is nowadays considered as a serious source pollution. At the same time, it contains high amounts of nutrients, especially potassium and phosphorus that could be recovered for agricultural purposes. The aim of the current experimental research work is to investigate the agronomic potential use of OMW based biochar produced from the slow pyrolysis at 500 °C of raw cypress sawdust (CS) impregnated with OMW (ICS-OMW-B). In order to understand the contribution of OMW, two additional biochars were produced from raw cypress sawdust (RCS-B) and cypress sawdust pretreated with potassium chloride (ICS-K-B). Results indicated that RCS impregnation by OMW significantly improved the produced biochar's chemical properties, especially its nutrients contents. Furthermore, in comparison with the other biochars, ICS-OMW-B application as an organic fertilizer showed promising results in terms of produced fresh and dry masses, as well as potassium bioavailability as assessed in test experiments with ryegrass. For instance, the dry matter masses of the rye-grass treated with ICS-OMW-B were about 23, 34 and 50 wt% higher than the ones measured for the tests using RCS-B, ICS-K-B and synthetic K-fertilizer as amendments, respectively. Besides, this biochar has a potential effect on the suppression of various pathogens existing in the tested agricultural soil. All these results demonstrated that the biochar generated from the slow pyrolysis of impregnated sawdust with OMW could be considered as attractive and promising organic fertilizer for acidic agricultural soils. Unlabelled Image • Cypress sawdust impregnated with olive mill wastewater was used to elaborate biochars. • The fertilizing potential of the biochars was evaluated through ryegrass growth tests. • Biochar enriched with olive mill wastewater is an efficient organic fertilizer. • The effect of biochar on soil aggregate stability and pathogen growth was assessed. • K and P bioavailabilities were estimated through the analyses of rye grass leaves. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) of wet solid wastes has been pointed out as an eco-friendly, flexible and highly efficient technology for the sustainable valorization of multiple sourced wastes. In this review paper, most recent studies on hydrochars (solid residue of the HTC process) production, characterization and application for wastewaters treatment was summarized and deeply discussed. The role of initial feedstock source nature and characteristics as well as the HTC experimental conditions including the temperature, the residence time and the pH media was assessed. Physical and chemical activation methods including the use of oxygen, steam, microwave, acids, alkaline, organics and salty solutions for the improvement of the physicochemical properties of the produced hydrochars are compared. The efficiency of these raw/modified hydrochars along with the involved mechanisms during organic (dyes) and mineral pollutants (heavy metals and nutrients) removal from aqueous solutions is also reviewed. Finally, this paper addresses the main challenges and also demonstrates insights on new directions for hydrochars research and development in the future. • Hydrochars showed a decrease in esters and hydroxyl groups compared to raw biomass. • Carbon content, minerals and polymeric structure influence hydrochars' adsorption capacity. • Solution temperature, pH and residence time impact hydrochar's efficiency. • Hydrochar's oxygen functional groups are reactive to heavy metals and organic molecules. • Post-activation improves significantly hydrochars' specific surface area. [ABSTRACT FROM AUTHOR]

Olive mill wastewater (OMWW) management is recognized as the major defy that olive oil industry is facing. Recently, we have established an eco-friendly strategy for the OMWW conversion into irrigation water sources, green biofuels and biofertilizers. This work is a part of a series of papers detailing the different steps established in this environmental friendly strategy for OMWW management. It deals with the bio-oil production and characterization during the pyrolysis of OMWW impregnated on olive pomace (OP) in a pyrolyzer pilot. Results show a bio-oil production yield of 36 wt% during the pyrolysis test. This yield could be attributed to the recovery of organic compounds from OMWW through OP impregnation and their conversion to bio-oil. The bio-oil properties show that viscosity and flash point values could reach the European standards. However, the lower heating values (26 MJ/kg) and the acidic character limit its direct use. These values are attributed to the higher water and oxygen contents. The GC/MS analysis confirms these properties showing the presence of phenolic molecules and long chain organic acids. Therefore, OMWW impregnation on OP and pyrolysis could be considered as a promising issue for bio-oil production. However, this bio-oil requires an upgrading step for a better valorization. • A strategy for olive mill wastes recovery is established using pyrolysis technique. • A bio-oil production yield of 36% confirms the OMWW organic matter valorization. • Bio-oil viscosity and flash point properties could reach biofuels Standards. • Bio-oil contains many components as phenolic molecules and long chain organic acids. • Oxygen and water contents, acidic pH require improvement before bio-oil direct use. [ABSTRACT FROM AUTHOR]

In order to set up a cost-efficient biorefinery in a Tunisian dairy industry, the production unit effluents are recovered. The main objective is to develop an optimum method for the production of bioethanol from whey. An energy analysis as well as environmental and economic analyses are performed for a bioethanol production plant. Four production scenarios are examined in order to determine the most provident as well as the less polluting ones. The process and cost models were developed using SuperPro Designer software which a simulation program that is able to estimate both process and economic parameters. This software uses energy and mass balances. The model can be used to assess the efficiency, the resources consumption, the profitability and the environmental impact of each scenario. The results demonstrate that the third scenario, in which a reverse osmosis procedure is added to concentrate the whey, a continuous stoichiometric reaction procedure is integrated to model the biotransformation in the fermenter and where streams are added in order to recycle the biomass, produces the highest amount of bioethanol with 1.65 MT/year but the second one (where no streams were added) is the most profitable one with revenues as high as 570 000 $/year. The corresponding cost of ethanol production is 0.271 US $ ethanol per liter. The net present value (NPV) and the return on investment (ROI) of each scenario are positive. Such result indicates that all these investments could be undertaken in order to find an eco-friendly issue for the dairy industry effluents. Cheese whey could serve as an alternative raw material for producing ethanol. [Display omitted] • A model of a cost-efficient biorefinery is built for Tunisian cheese whey recovery. • Lactose affects clearly the ethanol production. • Adding streams to recycle the biomass is efficient economically and ecologically. • Produce bioethanol from important amount of effluent without treatment. [ABSTRACT FROM AUTHOR]

Abstract: The current work tackles the problem of soil microbial growth and biofilm expansion assessment in infiltration percolation process in order to optimize the technique design and monitoring. Experiments were conducted on a sand filled PVC column fed at a pulsed rhythm of 8 sequences per day in order to maximize the soil aeration that generates a better oxygen renewal in the soil gas phase, enhances the oxidation of the oxidisable matters and improves sanitary performances. As we target the biofilm expansion study, we assessed the microbial biomass at different depths of the soil matrix (10, 25, 50 and 75 cm), by the chloroform fumigation–extraction and DNA extraction methods. Results showed that the microbial biomass increases with operating time especially between 10 and 25 cm depths until the 96th operating day (OPD) and decreases notably after this time. A highly significant positively correlation (r = 0.97) is registered between results of microbial biomass quantification by fumigation–extraction method (FEM) expressed as carbon material (biomass C) and those obtained by DNA extraction method (DNA-EM). In addition, we performed an enumeration of the biofilm total microbial flora using the solid medium cultivation method which corroborates the microbial biomass quantification results. In order to illustrate the biofilm shape generated by bacterial cells and extracellular polymeric substances (EPS)in the vicinity of the sand grains, we performed different scanning electron microscope (SEM) micrographs at different elapsed operation times. [Copyright &y& Elsevier]

Hydrothermal carbonization (HTC) is considered as a promising technique for wastes conversion into carbon rich materials for various energetic, environmental and agricultural applications. In this work, the HTC of olive mill wastewater (OMWW) was investigated at different temperatures (180–220 °C) and both, the solid (i.e., hydrochars) and the final process liquid derived from the thermal conversion process were deeply analyzed. Results showed that the solid yield was affected by the temperature, i.e., decrease from 57% to 25% for temperatures of 180 °C and 220 °C, respectively. Furthermore, the hydrochars presented an increasing fixed carbon percentage with the increase of the carbonization temperature, suggesting that decarboxylation is the main reaction driving the HTC process. The decrease in the O/C ratio promoted an increase of the high heating value (HHV) by 32% for hydrochar prepared at 220 °C. The process liquids were sampled and their organic contents were analyzed using GC–MS technique. Acids, alcohols, phenols and sugar derivatives were detected and their concentrations varied with carbonization temperatures. The assessment of the physico-chemical properties of the generated HTC by-products suggested the possible application of the hydrochars for energetic insights while the liquid fraction could be practical for in agricultural field. Unlabelled Image • Valorization of olive mill wastewater was studied using hydrothermal carbonization. • Characterization of the produced hydrochars was assessed by multiple techniques. • Carbonization process of the precursor was governed by decarboxylation mechanism. • Produced hydrochars presented a high calorific content (35.01 MJ/kg). • Final liquid fractions exhibited interesting organic compounds for agricultural use. [ABSTRACT FROM AUTHOR]

• Raw kenaf stems and its pyrolytic char are fully characterized. • Thermal properties of kenaf stems are more interesting than many other usual crops. • Kenaf stem derived char is very promising for pollutants removal or gas storage. • Kenaf derived char is suitable for soil amendments. • High SSA of the 500 °C-chars incite to activation process to get excellent AC. Kenaf stems are characterized in this present investigation in order to assess their suitability in energy recovery through a pyrolysis process and to identify sustainable applications of the generated biochar. In particular, the raw biomass properties are analyzed using numerous analytical techniques such as thermogravimetric analyses (TGA/DTG), X-Ray Fluorescence (XRF) and Scanning Electronic Microscopy (SEM). First, the thermogravimetric analyses monitor the pyrolysis parameters, control the proportion of its outputs and allow to extract the kinetic parameters. The latter is determined using Friedman, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) models. In a second step, Kenaf derived chars are produced at different pyrolysis temperatures and their physicochemical, morphological, textural and structural properties are determined using different techniques such as CO 2 adsorption, Raman Spectroscopy, and DRIFT Spectroscopy. The main results confirm the Kenaf potential for energy applications as its thermal properties are more interesting compared to other usual crops. The Kenaf stem derived char is also very promising for pollutants removal or gas storage as its surface area as well as its microporous structure are interestingly developed when increasing the pyrolysis temperature. Kenaf char could be also chemically or physically activated in order to be used for pollutants removal from gaseous and aqueous effluents. Finally, the XRF analysis indicated that contents in K and P elements are high. Ca and Mg are also major mineral species in the char. These contents indicate that Kenaf derived char could be also suitable for agricultural soil amendments. [ABSTRACT FROM AUTHOR]