Potential Low-cost Adsorbent Research Articles

Dual-function CoNi-LDH hollow porous spheres for morphology-driven adsorptive removal and photo-oxidative degradation of anionic dyes

The layered double hydroxides (LDHs) emerged as a class of low-cost potential adsorbents for organic pollutant separation, whereas the deep study of organic dye separation regulated by LDH hollow morphology under ambient conditions is still lacking. To address this gap, ZIF-67, Bulk-CoNi-LDH, and HPS-CoNi-LDH materials of different morphology and porosity were synthesized and investigated in the dye separation process. Methyl orange (MO), congo-red (CR), methylene blue (MB), and rhodamine B (Rhb) dyes were selected as model dye pollutants. The spectroscopic and structural analysis reveals the HPS-CoNi-LDH exhibits less-aggregated 2D nanosheets, high BET surface area of 163.2 m2/g, large pore size of 12.29 nm, greater positive surface charges (27.5 mV), superior optical (2.18 eV), and charge-separation capabilities as compared to Bulk-CoNi-LDH, Which provides potential sites for adsorptive and photo-degradation for anionic dyes under natural sunlight. Therefore, it achieves a remarkable removal efficiency of 92.6% for methyl orange (15 ppm) with a superior kinetic rate of 3.0×10−2 min−1 within 90 min, outperforming Bulk-CoNi-LDH and ZIF-67 having removal efficiency of 71.7% and 40.8%, and kinetic rate of 1.35×10−2 and 0.5×10−2 min−1, respectively. Poor removal efficiency and kinetic by ZIF-67 was mainly due to its smaller pore size (1.16 nm) and surface-confined charges (6.13 mV). Additionally, HPS-CoNi-LDH exhibits superb selectivity (at a ppm level) and excellent recyclability under ambient conditions. The mechanism of photo-catalytic reaction is discussed. These results delineate the hollow morphological LDH structure could be a worthy candidate for selective wastewater treatment and useful for sustainable conditions, which points the way to other crucial anionic micropollutant remediation.

Ultra-high selective removal of Congo red and Ciprofloxacin using unusual LDO modified biochar: Influence of emerging pollutants and application attempts

The porous biochar materials serve as effective adsorbents in water treatment. In this study, layered-double-hydroxide (LDH)(MgAl) was dispersed onto waste poplar powder through the co-precipitation method, followed by pyrolysis to prepare layered-double-oxides (LDO)/poplar carbon (CL-800) for ultra-high adsorption of Congo red (CR) and Ciprofloxacin (CIP). The CL-800 adsorbent possessed a well-developed layered porous structure that provides numerous adsorption sites and transport channels for dyes and antibiotics. Notably, CL-800 exhibited a significantly elevated level of selectivity and adsorption capacity towards CR and CIP reaching 93.0, 84.7 % and 4841.2, 744.0 mg/g, respectively. Various factors were considered to investigate the influence on CR and CIP adsorption, such as ion types, microplastics, and perfluorooctanoic acid. The adsorption capacity in complex water systems were also explored where CL-800 presented excellent removal efficiencies for CR (99.0 %) and CIP (89.6 %) in simulated wastewater along with good repeatability. Fixed-bed column tests also confirmed its potential as an effective adsorbent for wastewater purification due to continuous adsorption properties towards CR and CIP over time. Finally, the interaction mechanisms for CR/CIP adsorption processes onto CL-800 were possibly determined via various advanced techniques. This study provides new perspectives for providing a potential low-cost efficient adsorbent for organic wastewater treatment.

Investigation of gold adsorption by ironbark biochar using response surface methodology and artificial neural network modelling

Due to the importance and economic value of gold in various applications, recovering gold from waste streams like tailings and industrial wastewater is essential. Biochar with a high surface area and porosity is considered a potential low-cost adsorbent for gold reclaiming from aqueous media. Therefore, this study aims to develop a high-quality biochar with excellent physicochemical properties to efficiently remove gold from aqueous media. To accomplish this, biochar was obtained from pyrolysis of ironbark (IB) biomass at 500 °C which has a surface area of 493.79 m2/g. Subsequently, the biochar was investigated for adsorption of gold from aqueous media, which exhibited a maximum adsorption capacity of 858 mg/g. Isotherm results showed that the adsorption of gold by biochar followed the Langmuir model, indicating monolayer adsorption. Further, response surface methodology (RSM) and an artificial neural network (ANN) combined with the Salp Swarm Algorithm (SSA) were used to analyze the generated results (ANN-SSA). The RSM prediction model fit was adequate (R2 = 0.99). However, comparing the statistical data revealed that ANN-SSA outperformed RSM in predicting experimental results. Overall, this study suggested that biochar derived from IB biomass could be used as a potential adsorbent to recover gold from an aqueous solution. This article presents a unique and innovative study on the utilization of ironbark biochar for the purpose of gold adsorption.

Adsorptive removal of biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) from greywater using activated carbon prepared from tropical almond and palm kernel shells

This study assesses the reduction of 5-day biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) of household greywater using palm kernel activated carbon (PKAC) and tropical almond activated carbon (TAAC) produced from locally available materials in a kiln at 800oC and activated using steam at a flowrate of 120 mL hr-1. Brunauer-Emmet-Teller (BET) surface area determination revealed that PKAC had a larger surface area than TAAC. Scanning electron microscope (SEM) imagery of the carbons also revealed amorphous and large internal shapes for TAAC while crystalline and closed packed shapes for PKAC. X-ray diffraction (XRD) analysis indicated that the major component present in the PKAC and TAAC was carbon and other allotropes of carbon. Batch results showed that reduction of BOD5 and COD was affected by particle size. The maximum percentage reduction of BOD5 and COD by PKAC was 76% and 65% respectively while reduction by TAAC was 62% and 52% respectively. The adsorption process was well described by the Freundlich adsorption isotherm. The studies showed that PKAC is a better adsorbent for reducing BOD5 and COD from domestic greywater as compared with TAAC. The PKAC is a potential low-cost adsorbent for BOD5 and COD removal from domestic greywater.

Adsorption of Lead from Aqueous Solution Using Activated Carbon Derived from Rice Husk Modified with Lemon Juice

In the present work, activated carbon (RHAC-LJ) was synthesized utilizing rice husk as a carbon source that is activated with lemon juice. Moreover, the adsorptive capacity of RHAC-LJ in removing Pb(II) from aqueous solution was investigated. FTIR analysis revealed the presence of amides, alkenes, carboxyl and hydroxyl groups in RHAC-LJ. SEM micrographs illustrate that activation with lemon juice resulted in high pore volume and greater pore diameter. Activation using acid from lemon juice can remove impurities from the adsorbent surface. The surface area and pore volume of RHAC-LJ were determined to be 112.87 m2·g−1 and 0.107 cm3/g, respectively. Adsorption kinetics followed the pseudo-second-order equation (R2 = 0.9941) with a rate constant of 3.3697 g/mg·min for Pb (II), which indicates chemisorption to be the rate-determining step of the process. The BBD model using RSM was applied in studying the effects of pH, stirring speed and adsorbent dosage and their interactions on the removal efficiency of RHAC-LJ. Analysis of variance was used to examine the significance of the model, independent parameters, and their interactions. Moreover, a removal efficiency of 98.49% can be attained using the following optimal conditions: 197 rpm, pH 5.49, and adsorbent dosage of 0.3487 g. Overall, the present work illustrates RHAC-LJ as a potential low-cost adsorbent for the removal of Pb(II) from synthetic wastewater.

Tea-Waste-Mediated Magnetic Oxide Nanoparticles as a Potential Low-Cost Adsorbent for Phosphate (PO43−) Anion Remediation

In the current study, magnetic oxide nanoparticle-impregnated tea waste (TW-Fe3O4) is employed as an adsorbent to remove phosphate ions (PO43−) from an aqueous solution. By utilizing a variety of analytical methods, the TW-Fe3O4 nano-adsorbent was characterized by FE-SEM, TEM, EDX, BET, FTIR and XRD. The FE-SEM of TW-Fe3O4 demonstrated the adsorbent’s granular morphology with a variety of magnetic nanoparticle sizes and shapes. The XRD of TW-Fe3O4 showed two diffraction peaks at 2θ values 30.9° and 35.4°, which are in correspondence with the diffraction pattern of magnetite. The synthesis of a TW-Fe3O4 adsorbent with a greater surface area and porosity was demonstrated by BET analysis. Numerous adsorption factors like initial concentration of PO43− ion, pH of the medium, contact time, temperature and adsorbent dose were optimized for phosphate removal. The maximum removal of 92% was achieved by using the adsorbent dose of 1.2 g at 323 K (pH 5). Pseudo-second-order and intra-particle diffusion models were fitted to the sorption kinetic, whereas adsorption isotherm data were found well fitted to Freundlich and Dubinin–Radushkevich (D-R) models. The highest adsorption capacity of TW-Fe3O4 towards phosphate ions was 226.8 mg/g, which is significantly higher than other reported bio-adsorbents. According to thermodynamic data, phosphate adsorption at the solid–liquid interface was of an endothermic and spontaneous nature and characterized by enhanced inevitability.

The enhanced separation effect of synthesized hydroxyapatite incorporated with ethylenediamine-tetramethylene phosphonic acid for Zn2+ and Co2+ ions and the deep insight into mechanism

Hydroxyapatite (HAP) incorporated with ethylenediaminetetramethylene phosphonic acid (EDTMP) was prepared and used for the separation of the toxic Zn2+ and Co2+ heavy metal ions in an aqueous solution. When the doping amount of EDTMP was 20%, the adsorption capacity of 20ED-HAP composite for Zn2+ and Co2+ reached 229.5 mg/g and 162.4 mg/g, which was 11.0 times and 11.8 times that of synthesized HAP in the absence of EDTMP. The effects of different concentrations of common coexisting ions such as Na+, K+, Ca2+, and Mg2+ were explored, and the removal rate of Co2+ or Zn2+ in a simulated actual water environment was also investigated. The removal of cobalt ions by EDTMP-HAP complex included ion exchange and surface complexation mechanisms. In addition to the above two mechanisms, the separation of zinc ions involved the dissolution precipitation mechanism with the formation of CaZn2(PO4)2·2H2O. Moreover, the affinity between EDTMP and HAP was revealed via Independent Gradient Model based on the Hirshfeld partition of molecular density (IGMH) and Hirshfeld surface analysis. Meanwhile, the interaction mechanism between EDTMP and Co2+ or Zn2+ was explored in depth through Multiwfn wavefunction analysis. The prepared adsorbent could be used as a low-cost potential adsorbent for toxic Zn2+ and Co2+ ions.

Removal of boron in aqueous solution by magnesium oxide with the hydration process

Excessive boron in an aqueous solution will endanger the growth of animals and plants and the normal operation of industrial production. To solve the problem of boron pollution, magnesium oxide (MgO) was prepared by precipitation, hydrothermal and calcination to remove boron from aqueous solution. The change of MgO before and after adsorption was analyzed by SEM, BET, XRD, FT-IR, and XPS characterization and calculation methods. Surface hydration of MgO and its transformation to magnesium hydroxide (Mg(OH)2) may be the main process of adsorption on boron. In addition, the adsorption of boron by MgO is an exothermic process and has relatively mild adsorption conditions (pH: 7–9). The maximum adsorption amount could reach 202.43 mg/g within 6 h (pH ≈ 9, T = 25 °C), higher than most boron adsorbents. Moreover, MgO has a certain anti-interference to competitive ions and can be renewable in alkaline solutions. Therefore, MgO is a potential low-cost boron adsorbent.

Comparative adsorption of tetracycline onto unmodified and NaOH-modified silicomanganese fumes: Kinetic and process modeling

Silicomanganese fumes (SMF) are industrial waste and a potential low-cost adsorbent for the removal of contaminants from water. In this study, the adsorption performance of SMF and NaOH-modified SMF (SMF-Na) for the removal of tetracycline (TC) from an aqueous solution was investigated. The characterization results showed the presence of functional groups (SiO2, -OH and C-O-C), a considerably higher surface area of the SMF-Na (142.59 m2 g−1) compared to the SMF (7.73 m2 g−1). The TC adsorption was favored under acidic conditions (pH 2–3) and increased with an increasing amount of adsorbent. The adsorption equilibrium was achieved in 360 min, and the presence of Na+ ions insignificantly influenced the TC adsorption. The Avrami model fitted better to the kinetic data with R2 = 0.995. The isothermal data was well represented by the Redlich-Peterson and Langmuir model. The maximum monolayer adsorption capacity of SMF and SMF-Na was 117 and 129 mg g−1, respectively. The thermodynamic results confirmed that the TC adsorption was endothermic and predominantly governed by physical forces. The removal of TC onto SMF and SMF-Na was maintained above 90 % even after five regeneration cycles The results suggested that SMF-Na is a promising alternative adsorbent for the removal of tetracycline antibiotics from wastewater streams.

Superior efficacies adsorptions on hydrotalcite-like compound as dual-functional clay nanomaterial for heavy metals and anionic dyes

Layered double hydroxide (LDH) calcined material, noted as flower-like Mg(Al)xOy clay nanostructures, with a Mg2+/Al3+ ratio of 2/1 has been involved as a potential low-cost adsorbent for the removal of cadmium ion and Congo red (CR) dye from wastewaters. The characterization was performed by FE-SEM, BET, TEM, XRD, FT-IR, and XPS analysis. A detailed study regarding the influence of pH, flower-like Mg(Al)xOy clay nanostructures dose, initial concentration, contact time, temperature, and desorption study was conducted for cadmium ion. Both Freundlich and Langmuir models fit the obtained data. Based on the thermodynamic results, the adsorption process for cadmium ion using the proposed adsorbent is spontaneous. The flower-like Mg(Al)xOy clay nanostructures material presents good recyclability after three cycles of adsorption/desorption. Also, this report includes a preliminary study (effect of initial concentration, temperature and contact time) regarding the capacity of flower-like Mg(Al)xOy clay nanostructures material to remove an anionic dye, i.e. CR. Kinetic data for the removal of both pollutants were best fitted by the pseudo second order kinetic model. Since the structure of the prepared material can allow cadmium ion and CR dye to be adsorbed in high amounts (up to 625 mg/g for cadmium ion and 1666.6 mg/g for CR dye), the water quality may considerably be improved.

Efficient cadmium removal from synthetic wastewater using a bipolymeric/Fe3O4 nanocomposite loaded on coal tailings

ABSTRACT Recent attempts to produce effective adsorbents for wastewater treatment purposes have led to development of multiphase nanocomposite consisting of a bed, nanoparticle enhancer(s) and one or more polymeric modifiers. However, availability and final price have been always prohibitive factors challenging the wide application of many of multiphase adsorbents. In this research work, a novel bipolymeric/Fe3O4 nanocomposite loaded on coal tailings was synthesized using a two-step procedure and evaluated as a potential low-cost adsorbent for treating synthetic wastewater polluted by heavy metals. Starting material and synthesized quadriphase nanocomposite were characterized using different instrumental analysis techniques. The adsorptive capacity of the nanocomposite was assessed using response surface methodology (RSM) by considering the nanocomposite-to-cadmium ratio (7–233) and initial pH of solution (3–11) as operating factors and cadmium removal as process response. The significance of the effect of operating variables on removal efficiency was assessed and confirmed using analysis of variance (ANOVA) method. The maximum cadmium removal of 99.30% was obtained under optimum conditions including pH of 10 and quadriphase nanocomposite/cadmium ratio of 40 after 2 h of adsorption. Kinetics and multistep adsorption studies showed that an optimum adsorption of 97% could be obtained only after 1.2 min following a first-order single-step process. Isotherm plots revealed that cadmium adsorb as monolayer on the surface of synthesized quadriphase nanocomposite based on Temkin model with the highest correlation coefficient of 97.67% and the least relative error of 16.15%.

Applicability of Green Absorbents to Remove Lead (II) from Polluted Water: a Potential Low-cost Adsorbent

The present work represent potential bio-sorbent (banana and pomegranate peel) in nano size range, with a view to for adsorption of lead(II) ions from aqueous solution. Dose, adsorbate concentration, pH, time, and temperature factors were investigated. The most favorable stipulations for Pb (II) adsorption are 50 mg /L as initial concentration, 0.2 g as pomegranate and banana peels mass and pH 5.5 and 5.23for banana and Pomegranate peel. Removal data obey the Langmuir model with qmax of 25.64 mg/g for banana and 41.66 mg/g for Pomegranate peel. The kinetics of removal process was fitted well by a second -order equation. It was observed that that the Pb (II) ion adsorption process on the both bio-sorbents is spontaneous process, endothermic for banana while exothermic for pomegranate peel. A distinct improvement in the adsorbent surface was noted after adsorption process which demonstrated via scanning electron microscope.

Pseudo-stem banana fiber as a potential low-cost adsorbent to remove methylene blue from synthetic wastewater

In this work, pseudo-stem banana (Musa acuminata) (PBF) fiber was utilized as a potential low-cost natural adsorbent to uptake methylene blue (MB) dye from synthetic wastewater by batch adsorption process. Different adsorption factors like contact time, pH, initial concentration, and adsorbent dosage were explored and found that the separation process is strongly pH dependent. Additionally, the adsorption data were fitted with various adsorption isotherms like Langmuir, Freundlich, Temkin, and Dubinin–Radhushkevich models to detect the adsorption equilibrium phenomena. Reaction kinetics was inspected using pseudo-first-order and second-order kinetic models. Mass transfer and intra-particle diffusion analyses indicate the adsorption mechanism of the system described particularly in the context. Furthermore, scanning electron spectroscopy (SEM) and Fourier transformed infrared spectroscopy (FTIR) were conducted to get the morphology and surface properties of the adsorbent, respectively. As a result, the as-prepared banana fiber can be proposed as a cheap suitable adsorbent to separate dyestuffs from industrial wastewater.

Biochar Derived from Sesbania sesban Plant as a Potential Low-Cost Adsorbent for Removal of Methylene Blue

In this study, biochar made from the Sesbania sesban plant, under slow pyrolysis at 300°C was used to adsorb methylene blue (MB) in aqueous solution. The biochar properties were clarified by diverse analytical methods such as FTIR, SEM, and BET. The results indicated that the surface of biochar was relatively smooth, had porous texture, and stacked evenly. In addition, the biochar had a large specific surface area of 561.8 m2/g and the pHpzc value was 6.9. The effect of adsorbent dosage, initial pH, contact time, and concentration of dye solution on biochar were investigated. The optimum conditions for MB adsorption were found at the MB concentration of 50 mg/L, initial pH of 11, biochar mass of 0.6 mg, and contact time of 30 min. Under these optimal conditions, MB dye removal efficiency was above 90%. Adsorption isotherm data were fitted with the Langmuir isotherm model (R2=0.897) suggesting the adsorption was monolayer, and its maximum adsorption capacity was about 6.6 mg/g. The adsorption kinetic models showed that the linear pseudo-second-order by R2=0.999 was well fitted. The results indicated the enormous potential of Sesbania sesban plant to produce biochar as a low-cost and rather high-effective adsorbent for dye removal from wastewater as well as water quality improvement.

Adsorptive Removal of Azithromycin Antibiotic from Aqueous Solution by Azolla Filiculoides-Based Activated Porous Carbon.

Due to the shortage of freshwater availability, reclaimed water has become an important source of irrigation water. Nevertheless, emergent contaminants such as antibiotics in reclaimed water can cause potential health risks because antibiotics are nonbiodegradable. In this paper, we report the adsorptive removal of azithromycin (AZM) antibiotics using activated porous carbon prepared from Azolla filiculoides (AF) (AFAC). The influence of the adsorption process variables, such as temperature, pH, time, and adsorbent dosage, is investigated and described. The prepared AFAC is very effective in removing AZM with 87% and 98% removal after the treatment of 75 min, at 303 and 333 K, respectively. The Langmuir, Temkin, Freundlich, and Dubinin–Radushkevich isotherm models were used to analyze the adsorption results. The Freundlich isotherm was best to describe the adsorption isotherm. The adsorption process follows second-order pseudo kinetics. The adsorption was endothermic (ΔH°= 32.25 kJ/mol) and spontaneous (ΔS° = 0.128 kJ/mol·K). Increasing the temperature from 273 to 333 K makes the process more spontaneous (ΔG° = −2.38 and −8.72 KJ/mol). The lower mean square energy of 0.07 to 0.845 kJ/mol confirms the process’ physical nature. The results indicate that AFAC can be a potential low-cost adsorbent of AZM from aqueous solutions.

Use of kaolin as a potential low-cost adsorbent for the removal of reactive blue BF-5G dye

The objective of this work was to use kaolin as an adsorbent for synthetic effluent, based on the reactive blue dye BF-5G. Several analytical techniques were used to investigate the material's crystallinity, morphology, specific surface area and fundamental functional group of kaolin. In sequence, different pH values were studied using a finite bath system. In investigating the influence of pH, the adsorbent used showed superior performance at a pH value equal to 1. From this optimal value, kinetic studies were carried out with the ideal conditions of pH, concentration and adsorbents (pH = 1, C0 = 50 mg/L and kaolin used as adsorbent). The adsorption percentage is maximum at pH 1 and decreases with the basic strength of the dye solution.

Local Cuban bentonite clay as potential low-cost adsorbent for shark liver oil pool purification

Context: The shark liver of the species Ginglimostoma cirratun, Carcharhinus longimanus, and Carcharhinus falciformis, captured in the north-central coast of Cuba are a source of oil, that when extracted it must be purified due to its bad smell, taste and the amount of impurities it has. Aims: To evaluate the purification of the shark liver oil (SLO) pool of species Ginglimostoma cirratun, Carcharhinus longimanus, and Carcharhinus falciformis, by Cuban bentonite clay. Methods: The effects of bentonite dose, contact time and speed rate were studied using the 23 factorial designs. The parameters are evaluated in the experiment design: acidity value, p-anisidine value, peroxide value, Totox value and Bleaching performance. Response Surface Methodology modeling techniques were applied to model the process and their performance and predictive capabilities of the response (purification efficiency) was also examined. Results: The experiments showed that the oil is suitable for consumption after the purification process. The best treatment, which could reduce the impurities in the SLO pool, was a treatment with bentonite dose at 80 g/L, time at 15 min, and speed rate at 250 rpm. Cuban bentonite clay is a promising adsorbent candidate for the removal of impurities of the SLO. Conclusions: The local Cuban bentonite clay can be used as potential low-cost adsorbent for shark liver oil pool purification, as showed the experiments.

Eco-Friendly Adsorbent from Waste of Mint: Application for the Removal of Hexavalent Chromium

A serious environmental disaster is looming on the horizon due to the indiscriminate release of heavy metals into the soil and wastewater from human industrial practices. In this study, waste mint (WM) was used to remove chromium(VI) from aqueous solution using batch experiments. The adsorbent material (WM) was characterized using scanning electron microscopy coupled with energy dispersive analysis of X-ray spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). The adsorption parameters optimized were as follows: pH solution (2–11), initial concentration of Cr(VI) (10–50 mg/L), adsorbent dose (0.1–10 g/L), and temperature conditions (298 K, 308 K, and 318 K). The experimental data fitted well to the fractional power kinetic model (0.97≤R2≤ 0.99) and Langmuir isotherm (R2 = 0.984) with a maximum adsorption capacity Qmax = 172.41 mg/g. The thermodynamic parameters for Cr(VI) sorption were also calculated, confirming that the adsorption process was spontaneous and accompanied by an exothermic adsorption (−4.83 ≤ ΔG ≤ −3.22 kJ/mol and ΔH = −28.93 kJ/mol). The Cr(VI) removal percentage was within the range of 41–98%, and the highest removal was noted at pH = 2. The results of the present study suggest that WM is a potential low-cost adsorbent for the removal of chromium(VI) from aqueous solutions.

Potential low-cost carbon-based adsorbent from gold mine tailings for anionic dye removal.

In this study, a mesoporous carbon (CMK-3) was successfully synthesized using mesoporous silica (SBA-15) prepared from gold mine tailings (sample CGMT) for removal of anionic dye from aqueous solution. For comparison, CMK-3 was prepared by the same method from pure silica (sample CT), and the other CMK-3 sample was prepared by a one-pot route mixing with Pluronic P123 (sample CP). The effect of the carbonization time on the synthesis of all CMK-3 samples was investigated, and the samples were characterized by X-ray diffraction and N2 adsorption-desorption. The sample with the highest surface area was chosen as an adsorbent, for each CMK-3 obtained from different methods. Batch adsorption experiments were studied to determine the influence of pH, contact time, and initial dye concentration. The adsorption kinetics obeyed the pseudo-second-order model. All carbon-based adsorbents were observed to be quite effective for the removal of dye with adsorption percentage in the order of CP > CT > CGMT. The maximum adsorption capacities were 188.99 and 204.57 mg·g-1 for CT and CGMT, respectively. The comparative results of all carbon-based adsorbents show that CGMT can be applied as a low-cost alternative to CT for dye removal.

Adsorptive Removal of Pyridine from Aqueous Solution Using Natural Shale

The discharge of pyridine bearing wastewater into water bodies without a prior satisfactory treatment would pose significant public health risk as well as serious threat to the aquatic ecosystems. In this study, a natural shale from Yichang, China is investigated to determine its potential as a low-cost adsorbent for trace pyridine removal from wastewaters. The prepared shale samples without surface modification are characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscope (SEM). Kinetics and isotherms of pyridine from aqueous solutions onto shale are investigated on the basis of the experimental data. It is found that the shale samples with well-developed porosity are mainly composed of illite, quartz, calcite, chlorite and sericite. Several kinetic models (viz. pseudo-first-order, pseudo-second-order, two-constant rate, intra-particle diffusion and Elovich) as well as isotherm models (Langmuir, Freundlich and Temkin) are applied to test the experimental data for pyridine removal. The kinetics of the adsorption of pyridine by shale follows a pseudo-second-order rate law with the adsorption data being best described by the Freundlich isotherm model. The preliminary study shows that natural shale obtained from sedimentary basins may be used as a potential low-cost adsorbent for the removal of trace pyridine from effluents.