Initial Adsorbate Concentration Research Articles

Decolourization of malachite green dye by mentha plant biochar (MPB): a combined action of adsorption and electrochemical reduction processes

Adsorption behavior of mentha (mint) plant biochar (MPB) in removal of malachite green (MG) dye from aqueous solution was analyzed as a function of different pH (4.0-10.0), initial dye concentration (20-100 mg/L), contact time (0-45 min) and dose of adsorbent (0.05-0.3 g/100 mL). The zeta potential of the MPB particles was found to be -37.9 mV, indicating a negatively charged sorption surface of MPB particles. MPB was found to be more effective in removal of MG dye at pH 6.0 due to combined action of physico-chemisorption and a reductive electron transfer reaction. Results on the Brunauer-Emmett-Teller (BET) analysis of the N2 adsorption-desorption isotherm of MPB as adsorbent showed sigmoidal shape similar to the type IV isotherm and mesoporous nature. The cyclic voltammetric analysis of MG dye showed a reversible, coupled redox reaction at the interface of dye molecules and MPB particles. The maximum monolayer adsorption capacity (qmax) of MPB was found to be 322.58 mg g-1. The separation factor (RL) value was between 0 and 1, indicating a favourable adsorption of MG dye onto MPB. The results fitted well to a pseudo-second-order kinetic model. Further results from desorption experiments showed recovery of MG dye by about 50% in the presence of 1 N HCl.

Tailoring of nanozeolite NaX for enhanced removal of a phytoestrogen from its aqueous solutions

ABSTRACTThis study represents the application of nanozeolite NaX (NZX) synthesized by hydrothermal treatment without addition of any expensive structure directing agent for the highly effectual adsorption of biochanin A from aqueous solution. The characteristics and surface morphology of NZX were determined using FT-IR, SEM, TEM, BET, and XRD. The adsorption performance of NZX was analyzed at different conditions such as temperature, pH, contact time, adsorbent dose, and initial adsorbate concentration. The adsorption mechanism was well verified by pseudo-second-order kinetic and Redlich–Peterson isotherm models. The thermodynamic parameters revealed that the removal process was exothermic and spontaneous.

Ultrasound–assisted adsorption of toxic dyes by cottonseed cake: artificial neural networks, regression models and response surface optimization

In this study, dehydrated cottonseed cake as a low-cost and abundant byproduct in Turkey was utilized as an adsorbent for the decolorization of Reactive Blue 19 (RB19) and Reactive Yellow 145 (RY145) from aqueous solutions based on adsorption and ultrasound-assisted adsorption (UAA). Decolorization efficiency was optimized as a function of changes in process type, initial pH value, adsorbent concentration, temperature, reaction time, and initial dye concentrations of RY145 and RB19 based on response surface methodology (RSM) using Box-Behnken Design. The maximum decolorization efficiency of 99.9% for both RY145 and RB19 was obtained with ultrasound-assisted adsorption under the RSM-optimized conditions (with unity desirability) of 76.98 and 79.40 min reaction times, 233.20 and 254.29 mg L-1 initial dye concentrations, 1.37 and 1.44 g L-1 adsorbent concentrations, and 35.42 and 49.37 °C, respectively. The best-fit multiple non-linear regression models of decolorization efficiency with the highest adjusted coefficients of determination (R2adj) explained 99.52% and 99.48% of variations through adsorption of RY145 and RB19 and 98.14% and 98.01% of variations through UAA of RY145 and RB19, respectively, while artificial neural networks accounted for 99.82%.

ADSORBENT FOR EFFICIENT REMOVAL OF MERCURY(II) FROM AQUEOUS SOLUTION

Decontamination of mercury from aqueous media remains a serious task for health and ecosystem protection. Removal of Hg(II) from the aqueous solution by ZnO:S has been investigated and elucidated. The effect of various parameters such as solution pH, adsorbent dose, contact time, initial adsorbate concentration has been studied and optimized. The optimized parameters for metal ion are pH value of 2.4, the equilibrium time was attained after 30 min, and the maximum removal percentage was achieved at an adsorbent loading weight of 0.08 g. It was found that the adsorption capacity of ZnO:S increased with increase in the initial mercury concentration. The equilibrium and kinetic data were found to be in good agreement with Freundlich isotherm model.

Adsorptive Potential of Acid Modified Moringa Oleifera Wastes for Tannery Effluent Decontamination

Removal of chromium from tannery effluent was carried out using low-cost adsorbents derived from Moringa oleifera seed shells and pods adsorbents. The precursor was modified using acid (H2 SO4 ) impregnation method and characterized using CHNO/S elemental analyzer, FT-IR, SEM, TEM and PXRD. Physicochemical study of the tannery effluent was carried out and documented. Result shows that most physico-chemical parameters investigated for the effluent are above the permissible limit outlined by WHO. Initial concentration of the pollutant, Chromium (987 mg/L) exceeds WHO limit. The maximum adsorption capacity of AMMOS was found to be 137.4 mg/g and that of AMMOP was 277.3 mg/g for chromium removal. Column adsorption study was used to study the effect of experimental variables (pH, initial adsorbate concentration, contact time, adsorbent dosage and temperature), while RE% of Cr by the adsorbents was calculated and recorded for all experimental runs. The equilibrium study for the sorption of Cr was investigated using the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm model. The linearity of the respective models include: Langmuir (R2 of 0.271 for AMMOP and 0.7661 for AMMOS), Freundlich R2 values for AMMOS (0.8337) and AMMOP (0.6485) thus, presenting the Freundlich model as the most applicable isotherm model. Temkin and Dubinin-Radushkevich isotherm models gave poor fittings for Cr on the adsorbents. The rate and mode of diffusion is best explained using the Pseudo-second order kinetic and film diffusion respectively suggesting that the kinetics of the sorption process is controlled by diffusion through the liquid film surrounding the solid sorbent. The efficiency in remediation of effluent using the adsorbents as compared with commercial activated carbon at 95% confidence interval shows that there is no significant difference. This implied that the used of Moringa oleifera seed shells and pods for adsorbents is an economically viable approach to combat remediation challenges in the removal of Chromium from Tan chrome liquor.

Highly efficient removal of hazardous aromatic pollutants by micro-nano spherical carbons synthesized from different chemical activation methods: a comparison study

ABSTRACTGlucose-derived micro-nano spherical activated carbon (GAC) was synthesized through two-stage and three-stage chemical activation processes in different impregnation ratios (K2CO3: precursor). GAC was characterized by nitrogen adsorption/desorption isotherm, point of zero charge, scanning electron microscope, and Fourier transform infrared. The prepared spherical GAC and commercial non-spherical AC were applied to remove a cationic dye (methylene green 5; MG5), an anionic dye (acid red 1; AR1), and phenol. The batch adsorption experiments were conducted to analyse the effects of different operation conditions (i.e. solution pH, contact time, initial adsorbate concentration, temperature, and desorbing agent) on the adsorption process. The adsorption equilibrium was rapidly reached in kinetic experiments with a removal rate of 47–83% (within 1 min). The three-stage process-synthesized GAC exhibited the highest adsorption capacity, with the maximum adsorption capacity reaching at 1365 mg/g for MG5, 562 mg/g for AR1, and 322 mg/g for phenol adsorption. The process of MG5 and AR1 adsorption was endothermic (+ΔH°), while phenol adsorption was exothermic (–ΔH°). The primary adsorption mechanism was pore filling and π-π interactions. The pore of spherical GAC might be easily enlarged than that of non-spherical AC when the temperature of solution increased. Therefore, the spherical activated carbon can server as a green promising and renewable adsorbent for efficiently remove hazardous aromatic pollutants from aquatic environment.

Study on adsorption of methylene blue by a novel composite material of TiO2 and alum sludge.

A composite material of TiO2 and alum sludge (TiO2@AS) is reported in this paper. The samples of alum sludge (AS) and TiO2@AS were characterized using a field emission scanning electron microscope (FE-SEM), an energy dispersive spectrometer (EDS) and an Ultima IV X-ray diffractometer (XRD). In order to study the adsorption capacity and the adsorption mechanism of methylene blue by TiO2@AS in aqueous solution, three indexes — pH, adsorbent dosage and initial concentration of methylene blue — were investigated to evaluate the adsorption capacity of TiO2@AS. Moreover, thermodynamic, kinetic and isothermal model analyses of the adsorption process were carried out. The results showed that pH has little effect on the adsorption capacity. The maximum adsorption efficiency occurred at an optimized pH value of 11 for the aqueous solution. The adsorbed amount of methylene blue on TiO2@AS increased with the initial concentration of adsorbate and decreased with an increase in TiO2@AS dosage. The adsorption kinetics of methylene blue by TiO2@AS were in good agreement with the quasi-second-order kinetic model (R2 ≥ 0.9964), indicating that chemisorption is the main rate-controlling step. The Freundlich isotherm equation can best describe the experimental data (R2 = 0.9788). It is revealed that the adsorption is mainly multilayer adsorption. Because ΔG < 0 and ΔH > 0, the adsorption is a spontaneous endothermic process. Furthermore, the TiO2@AS can be regenerated under ultraviolet light, thus prolonging the service life of AS and facilitating a solution to the problem of adsorption plugging.

Biosorption of Congo Red and Methylene Blue by pretreated waste Streptomyces fradiae biomass - Equilibrium, kinetic and thermodynamic studies

Pretreated waste Streptomyces fradiae biomass was utilized as an eco-friendly sorbent for Congo Red (CR) and Methylene Blue (MB) removal from aqueous solutions. The biosorbent was characterized by Fourier transform infrared spectroscopy. Batch experiments were conducted to study the effect of pH, biosorbent dosage, initial concentration of adsorbates, contact time and temperature on the biosorption of the two dyes. The equilibrium adsorption data were analysed using Freundlich and Langmuir models. Both models fitted well the experimental data. The maximum biosorption capacity of the pretreated Streptomyces fradiae biomass was 46.64 mg g-1 for CR and 59.63 mg g-1 for MB, at a pH 6.0, with the contact time of 120 min, the biosorbent dosage of 2 g dm-3 and the temperature of 298 K. Lagergren and Ho kinetic models were used to analyse the kinetic data obtained from different batch experiments. The biosorption of both dyes followed better the pseudo-second order kinetic model. The calculated values for ?G, ?S, and ?H indicated that the biosorption of CR and MB onto the waste pretreated biomass was feasible, spontaneous, and exothermic in the selected temperature range and conditions.

Ghassoul – Moroccan clay with excellent adsorption properties

Ghassoul, Mg-rich clay consisting mainly of stevensite and containing also additional minerals (sepiolite, quartz, dolomite, gypsum, celestine) is mined in Morocco where the only known deposit in the world is located in Moulouya Valley in Fès-Meknès region. Ghassoul, formed by diagenetic transformation of dolomite in Tertiary fresh-water or brackish-water lacustrine environment, was used for centuries as a natural soap and shampoo. In 1884, the very first scientific report about this material was published by A. A. Damour who provided information about chemical composition of ghassoul. Over the next one hundred years, this material became a subject of geologists' interest until 1998 when the first study focused on practical applications of ghassoul was reported. Between 1998 and 2016, twenty-eight studies were published, twenty-four of which were focused on practical use. According to the studies, the ghassoul can be successfully used as an adsorbent of heavy metals and organic compounds, as a precursor of cordierite ceramics, and, recently, also as a component of functional composites for catalysis or photocatalysis. However, the greatest interest is still in adsorption.This review article is divided into three main sections. The first one provides information about chemical composition, crystallochemical formula, cation exchange capacity, specific surface area, and density of ghassoul. The second and the third section contain data obtained by various authors from experiments on adsorption of heavy metals (As, Cd, Cr, Cu, Hg, Mn, Pb, and Zn) or organic compounds (basic yellow 87, methyl violet, methylene blue, orange G, rhodamine B, metalaxyl, and tricyclazole), respectively. Dose of ghassoul, initial concentration of adsorbate, adsorption capacity, contact time, temperature, and pH are listed in two tables (the first one for heavy metals, the second one for organic compounds). Some of the articles contain tables comparing the adsorption capacity of ghassoul with adsorption capacities of other materials reported elsewhere. Comments on the comparisons are also provided in this article and it is shown that only few materials can compete with adorption capacity of ghassoul.

REMOVAL OF HEXAVALENT CHROMIUM USING TWO INNOVATIVE ADSORBENTS

Hexavalent chromium Cr(VI), a constituent of wastewater from many industries, is regulated by the Environmental Protection Agency (EPA) as one of the priority pollutants. Adsorption is an important technique that can be used for Cr(VI) removal from wastewater. The challenge in adsorption techniques is to find a cheap, widely available adsorbent that has a high adsorption capacity to Cr(VI). Dates stones (DS) and palm fiber (PF) are two agricultural wastes that are produced from palm trees. These adsorbent materials were tested in batch systems to investigate the different factors that may affect the adsorption process, e.g. adsorbent dose, initial adsorbate concentration, pH of aqueous solution and agitation time. Equilibrium models tested include Langmuir, Freundlich, Temkin and Dubinin-Radushkevich. Freundlich adsorption isotherm was found to best fit the experimental data. The maximum adsorption capacities obtained for DS and PF were 16 and 6 mg/g, respectively. Kinetic studies indicated that the adsorption of Cr(VI) on both DS and PF was fast in the first stage of the adsorption process. The equilibrium was reached in less than 2 h for both adsorption systems. The adsorption process was found to be second order with both adsorbent and adsorbate concentration to affect the adsorption process. Film diffusion and intraparticle diffusion models were found to simultaneously influence the adsorption. The adsorption process was found to be favorable and of physical nature.

Treatment of Wastewater Contaminated with Cu(II) by Adsorption onto Acacia Activated Carbon

In this study, the adsorption of Cu(II) ions from aqueous solutions onto Activated Carbon prepared from Acacia leaves. (AAC) was investigated. The experiments were performed in a batch system at different parameters (contact time, adsorbent dosage, initial concentration of adsorbate, agitation rate, temperature, particle diameter, and solution pH) were varied in order to establish the optimum conditions for copper removal using AAC, and the copper ions adsorption capacity was evaluated after equilibrium was attained. The results indicate that the removal was effective at low Cu(II) concentrations and a natural pH value, and the optimum conditions for Cu(II) removal operation from the synthetic solution investigated were 120 minutes, 300 rpm, and 0.375 mm as a contact time, agitation rate, and particle diameter respectively, and pH value equals to 6 at the temperature 30 1 oC. Also, the adsorbent dose of 0.5 g/100 ml was sufficient for the high removal of Cu(II) from the solution for studied batches which reaches up to 95.3, 77.42, 53.4, 37.6, 26.5, 18.4, 15.4, and 12.15% respectively for studied batches 100, 200, 300, 400, 500, 600, 800, and 1000 ppm respectively. The results obtained from this study show that the AAC can be used as a low-cost adsorbent for the complete removal of Cu(II) from an aqueous solution especially at low concentrations.

Removal of Acid Red 18 (Azo-Dye) from Aqueous Solution by Adsorption onto Activated Charcoal Prepared from Almond Shell

One of the most important environmental pollutants is azo dyes in textile wastewater. In this study, the removal of azo dye Acid Red 18 (AR 18) with initial concentration of 25-100 mg L−1 in aqueous solution by the adsorption process onto activated charcoal prepared from almond shell (AC-AS) was investigated. The effects of initial pH (2-12), contact time (15-120 min), adsorbent (0.2-2 g L-1) and initial concentration of AR 18 (25-100 mg L-1) on the removal efficiency of AR 18 solution were investigated. All experiments were performed on a synthetic wastewater. The efficiency of dye removal and Freundlich and Langmuir adsorption isotherms were compared as a function of decolorization and adsorption and kinetic behavior of AR 18. The maximum removal efficiency of AR 18 (i.e., 90.83%) was occurring with pH 2, contact time of 60 min, initial dye concentration of 75 mg L-1 and the adsorbent dose of 0.8 g L-1. The removal of AR 18 followed the Frundlich isotherm model (r2&gt;0.994). Fitting of obtaining data onto kinetic models showed the pseudo second-order reaction kinetics with respect to the dye concentration. This investigation revealed adsorption onto activated charcoal prepared from almond shell presents good efficiency for solution decolorization.

Removal of nickel and methylene blue from aqueous solutions by steel slag as a low cost adsorbent

Nowadays, wastewater from various industries contains a large number of harmful heavy metals and coloring agents, which have to be removed to restore the quality of the environment. In this study, the removal of nickel ions (Ni2+) and methylene blue (MB) from the aqueous solution using steel slag as a low cost adsorbent was investigated. The chemical and mineralogical compositions, as well as the surface area of slag, were analyzed by using X-ray fluorescence spectroscopy, X-ray diffraction, and the Brunauer-Emmett-Teller method (BET). The effect of several important parameters such as contact time, adsorbent dose, pH, temperature, and initial adsorbate concentration on the adsorption process was studied systematically by batch experiments. The adsorption data were well correlated with the Langmuir isotherm model by all samples. The maximum adsorption capacity of the raw slag samples was 36.49 mg/g for Ni2+ and increased from 0.68 to 1.98 mg/g for MB after being acid-activated. The determined thermodynamic parameters indicate that the adsorption of Ni2+ and MB on steel slag is spontaneous in nature, endothermic (for Ni2+), and exothermic (for MB).

Simulation of Cefoselis hydrochloride adsorption on macroporous resin in a fixed-bed column using orthogonal collocation

Abstract Adsorption operation is of great importance for separation and purification of semi-synthetic cephalosporin compounds in pharmaceutical industry. The adsorption dynamics of Cefoselis hydrochloride (CFH) on XR 920C adsorbent in fixed bed was predicted by the model of modified film-pore diffusion (MFPD). The intraparticle diffusion equation and mass balance equation in fixed bed are discretized into two ordinary differential equations (ODEs) using the method of orthogonal collocation which largely improves the calculation accuracy. The MFPD model parameters including the pore diffusion coefficient (Dp), external mass-transfer coefficient (kf), and the axial dispersion (DL) were estimated. The kf value was calculated by the Carberry equation, in which the effective diffusion coefficient De was fitted based on Crank Model through experimental data. Moreover, three key operating parameters (i.e., initial adsorbate concentration; flow rate of import feed, and bed height of adsorbent) and the corresponded breakthrough curves were systematically studied and optimized. Therefore, this research not only provides valuable experimental data, but also a successfully mathematical model for designing the continuous chromatographic adsorption process of CFH.

Investigate the adsorption mechanism of heavy metals as chromium ions (Cr+3) from different solutions using modified chitosan

The objective of this study is to assess the removal of Cr (III) ions onto modified chitosan-starch from aqueous solutions under both acidic and basic conditions. The effect of various parameters has been investigated via batch adsorption technique. Such parameters include initial concentration of adsorbate, agitation time, adsorbent dosage, chemical kinetics, and influence of temperature. The experimental data was fit well to Frendlich adsorption isotherm. The thermodynamic parameters such as ΔH, ΔS and ΔG were calculated, indicating that the adsorption was spontaneous and endothermic in nature.

Effect of Adsorbate Concentration to Adsorbent Dosage Ratio on the Sorption of Heavy Metals on Soils

AbstractAdsorbent dosage and initial adsorbate concentration are usually used as two factors for a batch sorption experiment to investigate the sorption characteristics of heavy metals on soils. In...

Silver nanoparticles immobilised on the activated carbon as efficient adsorbent for removal of crystal violet dye from aqueous solutions. A kinetic study

The focus of the present work is on exploiting the excellent structural properties of the nanomaterials. More specifically, it is demonstrated that Ag nanoparticles (AgNPLs) chemically immobilised onto activated carbon (AC-AgNPLs) can act as an effective solid sorbent for removal and/or minimisation of selected crystal violet (CV) dye from aqueous solutions by conducting experiments on water samples. Spectroscopic tools such as FTIR, SEM, TEM and XRD were used in the characterisation of the adsorbent before and after adsorption. The adsorbent dose, pH, contact time, rotation velocity, initial concentration of adsorbate and the temperature effects were examined to evaluate their role in the percentage elimination of crystal violet. Crystal violet uptake was favourable in alkaline media at pH>7.0, while the Langmuir model revealed CV monolayer adsorption capacity of 87.2mg/g. The pseudo second-order model fitted the data well and the thermodynamic parameters (ΔH, ΔS, and ΔG) of CV retention revealed that the uptake is endothermic and spontaneous in nature. When AC-AgNPLs was utilised, it removed a greater CV percentage from aqueous solution relative to AC. The mechanism of adsorption was explored using the intra-particle diffusion model and the liquid-film model. Desorption studies were made to elucidate recovery of the adsorbate and adsorbent for the economic competitiveness of the removal system. The AC-AgNPLs was successfully recycled for seven successive adsorption–desorption cycles indicating its high reusability.

Arsenic and fluoride removal by potato peel and rice husk (PPRH) ash in aqueous environments

ABSTRACTFinding appropriate adsorbent may improve the quality of drinking water in those regions where arsenic (As) and fluoride (F−) are present in geological formations. In this study, we evaluated the efficiency of potato peel and rice husk ash (PPRH-ash)-derived adsorbent for the removal of As and F from contaminated water. Evaluation was done in batch adsorption experiments, and the effect of pH, initial adsorbate concentration, contact time, and adsorbent dose were studied. Characteristics of adsorbents were analyzed using scanning electron micropcope (SEM) and Fourier transform infrared (FTIR) spectroscopy. Both the Langmuir and Freundlich isotherm models fitted well for F− and As sorption process. The maximum adsorption capacity of adsorbent for As and F− was 2.17 μg g−1 and 2.91 mg g−1, respectively. The As and Fi removal was observed between pH 7 and 9. The sorption process was well explained with pseudo-second order kinetic model. Arsenic adsorption was not decreased in the presence of carbonate and sulfate. Results from this study demonstrated potential utility of this agricultural biowaste, which could be developed into a viable filtration technology for As and F− removal in As- and F-contaminated water streams.

Efficient removal of bisphenol S from aqueous solution by synthesized nano-zeolite secony mobil-5

Nano-zeolite secony mobil-5 (NZSM-5) was synthesized by hydrothermal treatment, and modified by HDTMA-Br. The functionalized nano-zeolite (FNZSM-5) was applied for rapid uptake of bisphenol S (BPS) from aqueous phase (>95% BPS removal with FNZSM-5 as compared to 36% with NZSM-5). The alignments of particles in adsorbent were observed by SEM and TEM micrographs. The elemental phase and composition were analyzed by XRD patterns and EDS, respectively. The surface functional groups and physical parameters of adsorbent were characterized by FT-IR and DFT, respectively. Batch adsorption investigations were performed under diverse range of pH (2–12), temperature (25–50 °C), FNZSM-5 (0.1–1.5 g/L), and initial adsorbate concentration (1–10 mg/L). Solution pH in the range 2–4 had an important impact on BPS adsorption onto prepared adsorbent with optimal removal (95%) because of the electrostatic interactions. The equilibrium study of BPS removal under optimum parameters was well understood by Freundlich model, indicating multilayer adsorption process. The kinetic data was found to have the best fit with pseudo-second-order kinetic model, which specifies the occurrence of chemical adsorption in the sorption system. The thermodynamic parameters revealed that BPS adsorption was more favored at low temperatures.

An insight into the adsorption of diclofenac on different biochars: Mechanisms, surface chemistry, and thermodynamics

Biochars were prepared from feedstocks pinewood and pig manure. Biochar microparticles obtained through grinding were evaluated for the removal of emerging contaminant diclofenac (DCF) and the underlying mechanism were thoroughly studied. Characterization of biochar was carried out using particle size analyzer, SEM, BET, FT-IR, XRD, XPS and zeta potential instrument. Pig manure biochar (BC-PM) exhibited excellent removal efficiency (99.6%) over pine wood biochar (BC-PW) at 500 µg L−1 of DCF (environmentally significant concentration). Intraparticle diffusion was found to be the major process facilitated the adsorption. BC-PW followed pseudo first-order kinetics whereas BC-PM followed pseudo second-order kinetics. Pine wood biochar was largely affected by pH variations whereas for pig manure biochar, pH effects were minimal owing to its surface functional groups and DCF hydrophobicity. Thermodynamics, presence of co-existing ions, initial adsorbate concentration and particles size played substantial role in adsorption. Various isotherms models were also studied and results are presented.