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The present research work revolves around the evaluation of the elimination of the cationic dye Methylene Blue (MB) from an aqueous solution by the exploitation of natural clay (TMG) from South-East Morocco. Several physicochemical techniques were used to characterize our TMG adsorbate, namely: X-ray diffraction (XRD), Fourier transform infrared absorption spectroscopy (FTIR), differential thermal analysis (DTA), thermal gravimetric analysis (TGA), and zero charge point (pHpzc). The morphological properties and elemental composition of our material were identified using scanning electron microscopy coupled with an energy-dispersive X-ray spectrometer (SEM-EDS). The batch technique was used under different operating conditions to produce quantitative adsorption, namely the amount of adsorbent, dye concentration, contact time, pH, and solution temperature. The maximum adsorption capacity of MB on TMG was 81.185 mg g-1 for a concentration of 100 mg L-1 MB at pHinitial= 6.43, temperature 20 °C, and 1 g L-1 adsorbent. The adsorption data were examined by Langmuir, Freundlich, and Temkin isotherms. The Langmuir isotherm provides the best correlation with the experimental data, and the pseudo-second-order kinetic model is more appropriate for the adsorption of the MB dye. The thermodynamic study of MB adsorption indicates that the process is physical, endothermic, and spontaneous. The Box-Behnken method was applied to identify the optimal conditions for MB removal in the design of batch experiments. The parameters examined result in >99% removal.

This article deals with the valorization of local natural materials of vegetable origin, which are less expensive and non-toxic through their use in water treatment. We have shown that the acid solution (HCl, 0.5 N) pretreatment of the Carpobrotus edulis plant increases its adsorbent potential towards Methylene Blue and reduces the levels of soluble organic matter that can be released into the water. The bio-adsorbents were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Elemental Analysis (EDX), Zero Point of Charge (PHz), Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD5). The acid treatment allows a reduction in soluble organic matter characterized by a decrease in BOD5 and COD of 91.9% and 88.3% respectively. For the initial concentration of 100 mg/L of MB, the biomaterial obtained after acid treatment (HMCE) has an equilibrium adsorption capacity of 19.61 mg/g compared to 9.91 mg/g for the native plant (NCE). Acid treatment also reduces the amount of adsorbent required to achieve a maximum rate of adsorption. pH, temperature and ionic strength do not have a major influence on the adsorption of Methylene Blue on the biomaterials studied. This adsorption follows the pseudo-second order kinetic model and is represented by the Langmuir and Freundlich isotherms. It is a spontaneous and endothermic process.

Layered double hydroxide (LDH), also known as hydrotalcite or anionic clays, have attracted attention in recent years due to their applications in various fields, particularly in the water treatment sector. In this work, the MgAl layered double hydroxide was synthesized by urea method and used for the removal of methyl orange dye (MO) from aqueous solutions. The MgAl-LDH adsorbent was then characterized using different techniques such as; Scanning Electron Microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric and differential thermal analyses (TGA–DTA).The effect of some environmental parameters (contact time, adsorbent mass, initial dye concentration, ionic strength) on the removal of MO has been also investigated. The adsorption kinetic of methyl orange on the surface of MgAl-LDH material was best fitted by pseudo-second-order model. The maximum experimental adsorption capacity was fond to be 197.62 mg.g−1. According to the results of this study, it can be concluded that MgAl-LDH adsorbent can be used effectively for the removal of anionic dyes from industrial wastewater.

The recent interest in the adsorption of pollutants on biomaterials has been gaining widespread attention, especially in the utilization of natural materials of vegetable origin-based composite biomaterials. In this study, the equilibrium and the kinetics of Crystal Violet adsorption onto native Carpobrotus edulis Mediterranean plant, which is biodegradable and less expensive, was investigated. Experiments were carried out as a function of adsorbent dose (0.08–1 g), contact time initial (5–180 min), ionic strength of salt NaCl (0.05–0.5 M), and solution pH (2–12). pH and ionic strength do not have a major influence on the adsorption of Crystal Violet on the biomaterial studied. The adsorption process followed a kinetic model of the pseudo-second-order. These results suggest that the native Carpobrotus edulis plant could potentially be used as an environmentally friendly adsorbent for eliminating cationic dyes from aqueous solutions.

The infiltration-percolation process adopted at the M'zar wastewater treatment plant (WWTP) is a widely used treatment process capable of depolluting and decontaminating the effluent. The first objective of this study was to evaluate the purification performance of this treatment process with regard to the elimination of carbonaceous pollution and nitrate ions. The obtained results confirmed that infiltration-percolation is an advanced treatment technique for the treatment of organic pollution parameters such as: chemical oxygen demand (COD), biochemical oxygen demand measured after five days (BOD5) and total suspended solids (TSS). Nevertheless, this process contributes to the increase of nitrate ions by oxidation of nitrogen pollution at the sand filter level; consequently, this pollutant causes serious ecological problems, such as the eutrophication phenomenon. Therefore, it is therefore essential to reasonably control nitrates before they are released into the environment. The second objective of this work was to develop and valorize new low-cost, widely available and environmentally friendly adsorbents of animal origin. Raw shrimp shell (RSS), a biomaterial of animal origin, is abundant, available, renewable and non-toxic. It has physicochemical properties that can induce a significant adsorptive activity. The surface micro-morphology of the biomaterial was investigated using scanning electron microscope; while the qualitative element composition was analyzed using energy dispersive X-ray and infrared spectroscopies. For this reason, our research team proceeded to evaluate the effectiveness of crushed shrimp shell particles in order to remove nitrate ions from municipal wastewater effluents. The founded results of raw wastewater decanted (RWWD) and purified wastewater (PWW) are encouraging and show significant purification yields: 68% (RWWD) and 79% (PWW) for nitrate ions.

Layered double hydroxides (LDHs), known as a class of anionic clays, have attracted considerable attention recently due to their potential applications in different areas as catalyst materials, energy materials, and adsorbent materials for environmental remediation, especially for anionic pollutant removal. In this study, magnesium aluminum layered double hydroxide (MgAl-LDH) was synthesized by two methods: standard coprecipitation and urea hydrolysis. Their textural properties and morphologies were examined by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG) and differential (DTG) analysis, and point of zero charge (pHpzc). The specific surface area was calculated from BET adsorption equation. The results indicated that the crystallinity and the regularity of the samples prepared by urea hydrolysis were much preferable to those prepared by the coprecipitation method. Their sorption properties toward phosphate were investigated and the experimental evidence showed that, at the initial concentration of 100 mg L-1 and at room temperature, the LDH synthesized by urea hydrolysis had a percentage removal of 94.3 ± 1.12% toward phosphate ions while 74.1 ± 1.34% were uptaked by LDH synthesized by coprecipitation method, suggesting that the crystallinity affects the sorption capability. The sorption mechanism indicates that phosphate ions could be sorbed onto LDHs via electrostatic attraction, ligand exchange, and ion exchange.

This paper deals with the valorization of the native Carpobrotus edulis plant (C. edulis) as a bioadsorbent for the removal of toxic dyes such as Rhodamine B (RB) and Congo Red (CR). This plant was further characterized by BET, SEM, EDX, and FT-IR methods. The colorants were applied in a batch adsorption experiment that included measurements of adsorbent ratio, ionic strength, contact time, initial concentration, pH, and temperature. It was observed that for 100 mg/L initial dye concentration, 0.2 g of C. edulis showed maximum adsorption efficiency for RB (> 75%), while 0.4 g for CR (> 70%). For both dyes on the biomaterial tested, ionic strength and pH have no significant impact on the adsorption. Adsorption fits a pseudo-second order kinetic model and Langmuir isotherm. The optimum adsorbed amount of C. edulis was indicated at 56.18 and 19.84 mg/g for RB and CR, respectively. The results of the thermodynamic study show that the adsorption process of the dyes by the biomaterial is spontaneous and exothermic with a decrease in the randomness of the adsorption process. The results of the regeneration indicate that the bioadsorbent was efficiently recycled with 55.80% and 36.26% uptake for RB and CR dyes, respectively, after 3rd cycles of desorption-adsorption. Operational factors were studied using Taguchi’s experimental design. Our experimental results confirm the importance of the influence of initial concentration, adsorbent ratio, and contact time on adsorption with maximum adsorption of RB and CR was found to be 76.06% and 68.18% dye, respectively.

The objective of this work is to determine the kinetic and thermodynamic properties of adsorption of Pb(II) from aqueous solutions by synthetically prepared MgFeAl-CO3 as layered double hydroxide (LDH) adsorbent. Compared to other adsorbents for heavy metal removal from aqueous solutions, LDH materials possessed many advantages such as nontoxic synthesis, chemical stability, environmentally friendly, and facile separation from the water solution. The synthesis of LDH was achieved by a co-precipitation method. The reaction products were characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive spectroscopy and N2 sorption–desorption isotherm analysis. The adsorption rates were investigated. The effect of the parameters such as contact time, initial metal ion concentration, and temperature on the adsorption of the Pb(II) was studied. Equilibrium was achieved in 60 min and the equilibrium adsorption capacity was found to be increased with the increase in the Pb(II) initial concentration. The removal efficiency of Pb(II) increases from 59.50% to 71.15% when the temperature increases from 15°C to 60°C. The pseudo-first-order, pseudo-second-order, and Elovich kinetic models were tested and the first was found to fit better to the experimental data. The application of the intra-particle diffusion model demonstrates that the surface diffusion and the intra-particle diffusion occur in parallel during the adsorption of Pb(II) onto MgFeAl-CO3. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Redlich-Peterson, and Temkin isotherm models. The results indicated that the Redlich–Peterson and Langmuir isotherms were the most suitable models for the obtained experimental data and the Langmuir maximum adsorption capacity of the MgFeAl-CO3 is found to be 117.86 mg g-1at 298.15 K. The thermodynamic analysis of the adsorption of Pb(II) on MgFeAl-CO3 reveals that the present adsorption process is a spontaneous and endothermic reaction.

The MgAl-LDH adsorbent (2:1) was developed by the urea method and used as an adsorbent for the removal of methyl orange from aqueous solution. The synthesized adsorbent was characterized by a different analytical technique: scanning electron microscope SEM, X-ray diffraction (XRD) and infrared spectroscopy (FT-IR). The effect of adsorption parameters such as solution pH, initial concentration of dye, and the temperature was studied using a static system. X-ray diffraction analysis of the samples confirms the crystal structure of the MgAl-LDH material. The MgAl-LDH adsorbent was efficient in removing MO from aqueous solution, and maximum removal of 98.5 % was observed in the pH range from 2 to 10. The maximum adsorption capacity of MgAl-LDH (2:1) was calculated from the Langmuir isotherm; the maximum quantity is 1250 mg. g-1. The determination of the thermodynamic parameters indicates that the reaction between methyl orange and MgAl-LDH (2:1) is spontaneous and exothermic (ΔH°wastewater.

Increasing amount of organic dyes in the ecosystem particularly in wastewater has propelled the search for more efficient low-cost bio adsorbents. Different techniques have been used for the treatment of wastewater containing toxic dyes such as: biological degradation, oxidation, adsorption, reverse osmosis, and membrane filtration. Among all these processes mentioned, adsorption with low cost adsorbents has been recognized as one of the cost effective and efficient techniques for treatment of industrial wastewater from organic and inorganic pollutants. Clays as material adsorbents for the removal of various toxic dyes from aqueous solutions as potential alternatives to activated carbons has recently received widespread attention because of the environmental-friendly nature of clay materials. This chapter presents a comprehensive account of the techniques used for the removal of industrial cationic and anionic dyes from water during the last 10 years with special reference to the adsorption by using low cost materials in decontamination processes. Effects of different adsorption parameters on the performance of clays as adsorbents have been also discussed. Various challenges encountered in using clay materials are highlighted and a number of future prospects for the adsorbents are proposed.

In this study, Mg–Al layered double hydroxide (MgAl-LDH) was synthesized by the urea hydrolysis method and used as sorbent to remove phosphate from aqueous solutions. Structural and morphological studies show that MgAl-LDH was prepared successfully with good crystallinity. The influences of sorbent dosage, time, initial concentrations, solution pH, temperature and competitive ions on the phosphate uptake have been investigated. It has been found that the uptake of phosphate onto MgAl-LDH was rapid and reached equilibrium within 60 min. The kinetic data were studied in terms of the pseudo-first-order, pseudo-second-order, elovich and intraparticle diffusion kinetic models. The pseudo-second-order model best described the sorption process. The isothermal data are best fitted by Freundlich, suggesting that multiple processes may control the adsorption of phosphate on the MgAl-LDH. The maximum adsorption capacity at 25 °C was found to be 346.4 mg/g. The sorption mechanism of phosphate onto LDHs could be via electrostatic attraction, ligand exchange and ion exchange. Phosphates ion uptake in the presence of other ions decreases in the order NO3− > Cl− > SO42−. Thermodynamic experiments suggested that the phosphate adsorption was spontaneous (− ΔG°) and endothermic (+ ΔH°) and increased the randomness (+ ΔS°) in the system. Thus, MgAl-LDH prepared by urea hydrolysis method is an effective sorbent for the removal of phosphate from aqueous solutions.

In this study, Mg/Al layered double hydroxides (LDHs) with a molar ratio (Mg2+/Al3+) of 3 that were intercalated with carbonate ions were synthesized using either urea or coprecipitation. These hydroxides were used as adsorbents to remove methyl orange (MO) from aqueous solution. The adsorbents were characterized by two analytical techniques: scanning electron microscopy (SEM) and infrared spectroscopy (FTIR). The conditions applied in the adsorption experiments including pH, initial MO concentration, contact time, adsorbent dosage, ionic strength, and temperature—were varied. A pseudo-second-order model was found to most accurately reflect the adsorption kinetics of MO on the surfaces of LDH-Urea (layered double hydroxide prepared using urea) and LDH-Cop (layered double hydroxide prepared using coprecipitation). The maximum adsorption capacities of LDH-Urea and LDH-Cop, as calculated using the Langmuir isotherm, were 625 and 526.31 mg g−1, respectively, and the adsorption process was exothermic. The results of this study indicate that LDH-Urea and LDH-Cop are effective adsorbents for removing anionic dyes from industrial wastewater.

Dyes are defined as toxic, mutagenic, and dangerous pollutants to aquatic living organisms. Many adverse effects of these organic molecules on the environment such as decrease light penetration and photosynthesis which causes problems to aquatic groups, and which affect as well human health, because he is the first consumer of marine wealth, have led the researchers around the world to reduce this pollution. The wastewater must be treated carefully before discharge into main streams. Thus, great attention has been paid for many decades to the removal of dyes from industrial wastewater. Macroalgae also known as seaweeds belong to one of several groups of multicellular algae: brown, red, and green algae. This biomass can be used as dead material (adsorption) and even as living material (absorption) to remove various textile dyes. Hence, macroalgae are low-cost, non-toxic, and easily available biomaterials for the treatment of colored effluents. Adsorption of industrial dyes using marine macroalgae biomass can be an effective process and alternative to conventional methods. Macroalgal biomass is one of the most promising types of bio-adsorbents due to its rigid macrostructure, high uptake capacity, and immediate abundance. Some macroalgae have different affinities, depending on the chemical structure of each macroalga. In view of the pollution by organic pollutants and the possibility of using marine macro-algae, the present chapter was initiated to evaluate the adsorbent capacities of several macro-algae for the removal of industrial dyes in an aqueous solution. We highlight in this chapter (1) an overview on the chemical and structural properties of textile dyes, (2) toxicity and pollution of textile dyes, (3) the available technologies for hazardous organic dyes removal, (4) physicochemical parameters affecting adsorption of hazardous organic dyes, and (5) the current knowledge on the potential of using adsorbents prepared from macroalgae for the removal of dyes from aqueous solutions.

In the present study, a low-cost bio-adsorbent is developed from the naturally and abundantly available dried Mediterranean plant which is biodegradable. The bio-adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR) and point of zero charge (PZC). A study on the adsorption kinetics and isotherms was performed applying the optimized conditions. The equilibrium data for the adsorption of acid blue 113 on dried plant is tested with various adsorption isotherm models such as Langmuir, Freundlich, Temkin and Dubinin–Radushkevich equation. The Langmuir isotherm model is found to be the most suitable one for the acid blue 113 (AB113) adsorption using dried C. edulis plant and the theoretical maximum adsorption capacity obtained with the application of Langmuir isotherm model is 8.2 mg.g−1 at room temperature. The adsorption process follows the second-order kinetics and the corresponding rate constants are obtained. The thermodynamic parameters suggest that the adsorption process is spontaneous and exothermic nature. It can be concluded that the dried C. edulis adsorbent studied has good perspective to be used as adsorbent material in anionic dyes removal from industry effluents.

Water pollution is an alarming problem in developing countries. Dried algae can be considered as potential and suitable bio-sorbents due to their fast and easy growth and high availability. The special surface properties of these algae allow them to adsorb different types of organic and inorganic pollutants from solutions. In this context, the removal of anionic acid blue 113 dye (AB113) from aqueous solutions by dried Corallina officinalis alga as low-cost bio-sorbent was chosen as a case study of a typical remediation process of water contaminants. The effect of various environmental and physicochemical parameters has been studied. The results show that the equilibrium adsorption was established within 120 min. The sorption phenomenon was investigated by determining the process kinetics at different concentrations and the adsorption isotherms at different temperatures. The kinetics results showed that the pseudo second-order kinetics model generates the best agreement with the experimental data. The modeling results showed that linear Langmuir and Freundlich models appear to fit the adsorption data better than Temkin model for the adsorption of AB113 onto dried C. officinalis alga. It can be concluded that C. Officinalis alga can be successfully used as adsorbent.

This work aims at improving ceramic membrane selectivity by modifications of surface using inert solid biomaterials as adsorbents. Filtration experiments were performed with a ceramic tubular membrane cordierite/ZrO2 (pore size 0.2 μm). This membrane has been modified by formation of a dynamic layer at the surface of the microfiltration membrane during the circulation of vegetal suspension. This study reports the results of the retention of by this new membrane system and we compare these results with those of the non-modified membrane (cordierite/ZrO2). The influence of concentration was also studied. The images obtained by scanning electron microscopy of the surface and the transverse section of the modified membrane are commented. The results obtained are encouraging and show the possibility of using this process for the purification of polluted water by ions such as .

This paper reports the feasibility of using dried plants to remove As(V) from aqueous solution under different experimental conditions. For this purpose, micro-particles of both Calami rhizoma and Withania frutescens plants, have been separately used without pre-treatment as natural adsorbents. Effect of various process parameters, namely adsorbent dose, contact time, initial As(V) concentration, temperature, and pH has been studied. The experimental data were analyzed using Freundlich, Langmuir, and Temkin isotherm models to determine the mechanistic parameters related to the adsorption process. It was found that the Langmuir and Freundlich models fitted well. Thermodynamic parameters, viz, free energy change (ΔG0), enthalpy change (ΔH0), and entropy change (ΔS0), were also determined. The negative values of free energy change indicated the spontaneous nature of the adsorption and the positive values of enthalpy change suggested the endothermic nature of the adsorption process. The presence of some competing ions like Cl−, NO 3 - , Mg2+, Cd2+, Cu2+, and Zn2+ did not affect the arsenate uptake or removal, whereas HPO 4 2 - strongly interfered negatively.

Contamination of surface water and groundwater by organic pollutants is a serious problem due to their persistence, bioaccumulation and biomagnification through food webs. Since the removal of dyes from wastewater is considered an environmental challenge and government legislation requires textile wastewater to be treated, therefore there is a constant need to have an effective process that can efficiently remove these dyes. The aim of the present study is to evaluate the potentiality of dried Carpobrotus edulis plant as low-cost adsorbent for the removal of the industrial acid blue 113 dye from aqueous solutions using the batch equilibration technique. The effects of different physicochemical parameters such as adsorbent dose, contact time, initial dye concentration, solution pH and temperature on adsorption rate of anionic AB113 dye on microparticles of dried C. edulis plant were investigated. The experimental data were analyzed by using mathematical models to determine the thermodynamic parameters. The negative values of free energy change indicated the spontaneous nature of the adsorption and negative value of enthalpy change suggested the exothermic nature of the adsorption process. These results indicate that dried C. edulis plant as an environmentally friendly adsorbent could be potentially used for the removal of anionic dyes from aqueous solutions.

This study reports on the removal of Cu(II) ions from an aqueous solution by adsorption onto dried Carpobrotus edulis plant in a column system. The effect of various process parameters, namely m/V ratio, contact time, initial Cu(II) concentration and pH was studied. The experimental data were analyzed using Freundlich and Langmuir isotherm models to determine the mechanistic parameters related to the adsorption process. The results showed that the adsorption of Cu(II) ions by dried C. edulis increases with the increase of contact time, adsorbent dose, pH and initial Cu(II) concentration in the solution. The maximum adsorption of Cu(II) is reached after one hour of contact time at initial copper concentrations ranging between 10 and 100 mg/L. The m/V ratio of 25 g/L was optimal to obtain a maximum adsorption of copper ions. The maximum adsorption percentage of C. edulis is equal to 94.4%. These results showed that the dried C. edulis plant could be considered as a potential adsorbent material for the removal of Cu(II) from wastewater, using a column adsorption mode.

Low cost adsorbents were prepared from dried plants for the removal of heavy metals, nitrate, and phosphate ions from industrial wastewaters. The efficiency of these adsorbents was investigated using batch adsorption technique at room temperature. The dried plant particles were characterized by N 2 at 77 K adsorption, scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and phytochemical screening. The adsorption experiments showed that the microparticles of the dried plants presented a good adsorption of heavy metals, phosphate, and nitrate ions from real wastewaters. This adsorption increased with increasing contact time. The equilibrium time was found to be 30 min for heavy metals and nitrate ions and 240 min for phosphate ions. After the adsorption process, the Pb(II) concentrations, as well as those of Cd(II), Cu(II), and Zn(II) were below the European drinking water norms concentrations. The percentage removal of heavy metals, nitrates, and phosphates from industrial wastewaters by dried plants was ∼94% for Cd 2+ , ∼92% for Cu 2+ , ∼99% for Pb 2+ , ∼97% for Zn 2+ , ∼100% for NO ― 3 and ∼77% for PO 3― 4 ions. It is proved that dried plants can be one alternative source for low cost absorbents to remove heavy metals, nitrate, and phosphate ions from municipal and industrial wastewaters.

In the present work, Pb(II) and Cd(II) ion adsorption onto inert organic matter (IOM) obtained from ground dried plants: Euphorbia echinus, Launea arborescens, Senecio anthophorbium growing in semi-arid zones of Morocco and Carpobrotus edulis as the Mediterranean plant has been studied. A suspension of plant deroed micro-particles adsorbs lead and cadmium present as ionic species, with a higher affinity for Pb(II). The kinetics and the maximum capacity adsorption depend on the type of plant as well as on the metal ions (atomic weight, ionic radius and electronegativity). The adsorption process is affected by various parameters such as contact time, solution volume to mass of plant particles ratio (m/V), particle size, solution pH and metal concentration. A dose of 25 g/l of adsorbent was optimal to obtain maximum adsorption of both metal ions. The maximum metal uptake was obtained with particles of organic matter of E. echinus > S. anthophorbium > L. arborescens, however, the differences are rather small. Two different waste water types (domestic and industrial) were tested and good results were obtained for removal of Pb(II) and Cd(II) at more than 90%. The removal of the metal and mineral ions waste water was observed for PO43− at 88%, for NO3− at 96.5% and for metal ions (Pb(II), Cd(II), Cu(II) and Zn(II)) at about 100%, using IOM as absorbent.

The presence of arsenic in waters, especially groundwater, has become a worldwide problem in the past decades. The current regulation of drinking water standard has become more stringent and requires arsenic content to be reduced to a few parts per billion. There are numbers of arsenic removal methods, which include coagulation followed by precipitation, membrane separation, anion exchange, etc. The use of low-cost adsorbent obtained from an environmentally friendly materials, has been investigated as a replacement for the current expensive methods of removing arsenic from solution. Natural materials or waste products from certain industries with a high capacity for arsenic can be obtained, employed, and disposed of with little cost. Modification of the adsorbents can also improve adsorption capacity. The aim of this article is to review briefly arsenic chemistry and previous and current available technologies that have been reported in arsenic removal. The technical feasibility of various low-cost adsorbents for arsenic removal from contaminated water has been reviewed. Key words: Arsenic speciation, methods of arsenic removal, low-cost adsorbents, wastewater.

A low-cost adsorbent and environmentally friendly adsorbent from Carpobrotus edulis plant was used for the removal of NO(3)(-), H(2)PO(4)(-), Pb(2+) and Cd(2+) ions from single, binary and multi-component systems. The efficiency of the adsorbent was studied using batch adsorption technique under different experimental conditions by varying parameters such as pH, initial concentration and contact time. In single component systems, the dried C. edulis has the highest affinity for Pb(2+), followed by NO(3)(-), Cd(2+) and H(2)PO(4)(-), with adsorption capacities of 175mg/g, 125mg/g, 28mg/g and 26mg/g, respectively. These results showed that the adsorption of NO(3)(-) and H(2)PO(4)(-) ions from single and binary component systems can be successfully described by Langmuir and Freundlich isotherms. Freundlich adsorption model, showed the best fit to the single and binary experimental adsorption data. These results also indicated that the adsorption yield of Pb(2+) ion was reduced by the presence of Cd(2+) ion in binary metal mixture. The competitive adsorption of NO(3)(-), H(2)PO(4)(-), Pb(2+) and Cd(2+) ions on dried C. edulis plant shows that NO(3)(-) and H(2)PO(4)(-) anions are able to adsorb on different free binding sites and Pb(2+) and Cd(2+) cations are able to adsorb on the same active sites of C. edulis particles. The dried C. edulis was found to be efficient in removing nitrate, phosphate, cadmium and lead from aqueous solution as compared to other adsorbents already used for the removal of these ions.

The enrichment of marine particles with selenium cannot be explained as that with metals present in cationic form by complexation with anionic functional groups of adsorbed organic matter. Physicochemical data obtained using a model system are reported. The surface of the particles is modelized by a mercury electrode whose surface charge density can be easily changed, covered by a layer of adsorbed polymers. Studies with different kinds of macromolecules and salts show a specific interaction between adsorbed polyalanine and selenite. The results can be explained by the concordance of the distances between two oxygen atoms in this oxyanion and between two amine groups of the adsorbed polypeptide. A similar mechanism could occur in marine aggregates whatever their nature, as long as they contain amine groups at their surface which result in this concordance. Some prospects derived from the results are discussed.

A new adsorbent for removing metallic elements, nitrate and phosphate ions from municipal and industrial wastewaters has been investigated. This new adsorbent consists of micro-particles of dried Withania frutescens plant (500 μm). Batch experiments were conducted to evaluate the removal of metallic elements and anions from raw wastewaters by W. frutescens particles. The results show that the micro-particles of W. frutescens plant presented a good adsorption of metallic elements, nitrate and phosphate ions from both real wastewaters. This adsorption increased with increasing of contact time. The percentage of metallic elements removal from industrial wastewater by W. frutescens plant was 98 ≈ 99% for Pb(II), 92 ≈ 93% for Cd(II), 91 ≈ 92% for Cu(II) and 92 ≈ 93% for Zn(II). The maximum adsorption capacity was dependent on the type of ions. The results also indicate that the values of chemical oxygen demand (COD) decrease after the contact with W. frutescens particles. Based on the results it can be concluded that the dried W. frutescens plant appears to be an economical and environmentally friendly material for wastewater treatment.

It is shown that some of our recent experiments, reported herein, carried out with halide solutions in the presence of a dissolved polymer (polyethylene oxide, PEO) throw more light on this subject

This paper reports on fullerene C60 and C70 transport across hydrophilic membrane materials consisting of a poly(vinyl alcohol) matrix on which γ-cyclodextrin moieties were attached as molecular recognition sites. The rate-limiting step of the membrane transport was demonstrated to be dissociation of the inclusion complex at the stripping interface. Copyright © 2003 Society of Chemical Industry