Plasma Treated Sepiolite: A New Adsorbent for Removal of Malachite Green from Contaminated Water

Surface modification of clay materials has become an important issue to improve the efficiency of the adsorbent. The adsorption capacity of the clay material can be increased by thermal or chemical modifications. In this study, plasma technology was applied for the surface modification of sepiolite to improve the removal of malachite green from contaminated water. This study is novel in preparing and examining the effectiveness of sepiolite in adsorption of malachite green from contaminated water. To achieve the aim, plasma application time, CO₂, N₂, or Ar plasma gases effect and pH were investigated with respect to the adsorption capacity of MG. The surface properties of raw and plasma treated sepiolite were investigated with SEM, FTIR, BET surface area and XRD measurements. The monolayer adsorption capacity was found to be 143 mg/g.     

Kinetic,mechanism and equilibrium studies on removal of Pb(II) using <Emphasis Type="Italic">Citrus limettioides</Emphasis> peel and seed carbon

The sorption behaviour of Pb(II) ions onto activated carbon prepared from Citrus limettioides peel (CLPC) and seed (CLSC), which is a novel waste material, was evaluated as a function of contact time, pH, adsorbent dose, ionic strength, initial metal ion concentration and temperature in batch adsorption processes with raw Citrus limettioides peel (CLP) and seed (CLS). The maximum uptake of lead(II) ions was obtained at pH range 4.0–6.0 for CLPC, CLSC and 5.0–6.0 for raw materials (CLP, CLS). The optimal contact time was found to be 3 h. Surface morphology and functionality of the adsorbent were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis and Fourier-transform infrared (FT-IR) spectroscopy. The equilibrium data fit well with the Langmuir isotherm, confirming monolayer coverage of lead(II) ions onto CLP, CLPC, CLS and CLSC. The Langmuir monolayer adsorption capacity of CLP, CLPC, CLS and CLSC was found to be 123.60, 166.67, 15.32 and 142.86 mg/g. The calculated thermodynamic parameters showed that the sorption process was feasible, spontaneous and exothermic in nature. Kinetic studies demonstrated that adsorption of lead(II) ions followed a pseudo-second-order equation, suggesting that the adsorption process is presumably chemisorption. The adsorbents were tested for removal of Pb(II) from electroplating wastewater in connection with the reuse and selectivity of the adsorbents.     

Fast Removal and Recovery of Methylene Blue by Activated Carbon Modified with Magnetic Iron Oxide Nanoparticles

A magnetic adsorbent was synthesized by modification of activated carbons with magnetic iron oxide nanoparticles (AC‐MIONs). The preparation method is fast and could be carried out in an ordinary condition. The AC‐MIONs were used as quite efficient adsorbents for separation of methylene blue (MB) from aqueous solution in a batch process. The effect of different parameters such as pH, temperature, electrolyte concentration, contact time and interfering ions on the removal of MB were studied. The adsorption data were analyzed by Langmuir and Freundlich isotherm models and a maximum adsorption amount of 47.62 mg g^‐1 and a langmuir adsorption equilibrium constant of 3.0 L mg^‐1 were obtained. The obtained results revealed that AC‐MIONs were effective adsorbents for fast removal of MB from different aqueous solutions. This adsorbent was successfully used for removal of MB from Karoon River water.     

Carbon Dioxide/Methane Separation by Adsorption on Sepiolite

In this work,the use of sepiolite for the removal of carbon dioxide from a carbon diox- ide/methane mixture by a pressure swing adsorption(PSA)process has been researched.Adsorption equilibrium and kinetics have been measured in a fixed-bed,and the adsorption equilibrium parameters of carbon dioxide and methane on sepiolite have been obtained.A model based on the LDF approxima- tion has been employed to simulate the fixed-bed kinetics,using the Langmuir equation to describe the adsorption equilibrium isotherm.The functioning of a PSA cycle for separating carbon dioxide/methane mixtures using sepiolite as adsorbent has also been studied.The experimental results were compared with the ones predicted by the model adapted to a PSA system.Methane with purity higher than 97% can be obtained from feeds containing carbon dioxide with concentrations ranging from 34% to 56% with the proposed PSA cycle.These results suggest that sepiolite is an adsorbent with good properties for its employment in a PSA cycle for carbon dioxide removal from landfill gases.     

Removal of chromium from water using pea waste – a green approach

Abstract

Agro-waste materials have carboxylic and phenolic groups that play the main role in metal adsorption. The advantages of these materials include easy availability, low cost, and reasonable metal removal capacity. One of the materials (usually considered as waste) is pea waste (pods). Present work comprises adsorption of chromium from aqueous solution using powder of pods of garden peas (Pisum sativum) in batch. Important parameters like adsorbent dose, pH, contact time, and agitation speed were studied. Adsorption equilibrium was explained by Langmuir, Freundlich, and Temkin isotherms. Maximum chromium uptake (q _m) was 3.56 mg/g of adsorbent. Heat of adsorption, as evaluated by Temkin isotherm was 1.96 kJ/mol. It is proposed that pea pods can be an effective and environmentally benign (green) adsorbents for removal of chromium from industrial effluents and waste waters.     

Applicability of waste materials--bottom ash and deoiled soya--as adsorbents for the removal and recovery of a hazardous dye, brilliant green

Deoiled soya, an agricultural waste material, and bottom ash, a waste of power plants, have been successfully used for the removal and recovery of the hazardous water-soluble dye brilliant green from water. To remove the dye from water, batch adsorption studies have been carried out by observing the effects of pH, concentration, amounts of adsorbents, size of adsorbent particles, etc. Attempts have also been made to monitor the adsorption process through Langmuir, Freundlich, Tempkin, and D-R adsorption isotherm models. Relevant thermodynamic parameters have also been calculated from these models. The adsorption process has been found endothermic and feasible at all the temperatures. The kinetics of the adsorption was also recorded and indicates pseudo-second-order kinetics in both cases. Kinetic operations also reveal the involvement of a film diffusion mechanism for the deoiled soya adsorption at all the temperatures, while bottom ash undergoes through a particle diffusion mechanism at only 30 °C and at higher temperatures a film diffusion mechanism operates. Bulk removal of the dye has been carried out through column studies for both adsorbents. Attempts have also been made to recover the dye from exhausted columns by eluting sulfuric acid of pH 3.     

Methylphenols removal from water by low-cost adsorbents

A comparative study on the adsorption of methylphenols on adsorbents prepared from several industrial wastes has been carried out. The results show that extent of adsorption on carbonaceous adsorbent prepared from fertilizer industry waste has been found to be 37.3, 40.5, 65.9, and 88.5 mg/g for 2-methylphenol, 4-methylphenol, 2,4-dimethylphenol, and 2,4,6-trimethylphenol, rspectively. As compared to carbonaceous adsorbent, the other three adsorbents viz. blast furnace sludge, dust, and slag adsorb methylphenols to a much smaller extent. This has been accounted for due to the carbonaceous adsorbent having a larger porosity and consequently higher surface area. The adsorption of phenols on this carbonaceous adsorbent as a function of contact time, concentration, and temperature has been studied by the batch method. The adsorption has been found to be endothermic and data conform to the Langmuir equation. The analysis of data indicates that adsorption is a first-order process and pore diffusion-controlled. The efficiency of the carbonaceous adsorbent was assessed by comparing the results with those on a standard activated charcoal sample. It was found that the carbonaceous adsorbent is about 45% as efficient as standard activated charcoal and can therefore be employed for the removal of methylphenols from wastewaters.     

Removal of malachite green by adsorbents from paper industry waste materials

The objective of this work is to study the removal of malachite green (MG) from water by adsorbents obtained from pyrolysis of two paper industry waste materials: one de-inking paper sludge (HP) and one organic sludge from virgin pulp mill (RT). Both adsorbents showed elevated MG removal. Maximum adsorption Q ₀ obtained by Langmuir equation was higher for the adsorbent from HP (HP-3, 982 mg/g) than RT (RT-3, 435 mg/g). However, K _L (Langmuir) and 1/n (Freundlich) indicated that affinity and intensity of adsorption is higher for the adsorbents from RT. Thermal analysis (TG, DTG and DTA) of adsorbents before and after MG removal was performed in N₂ atmosphere.     

Adsorption kinetic and isotherm studies of Azure A on various activated carbons derived from agricultural wastes

The present study narrates the eminent role of agricultural wastes as adsorbents viz., Indian almond shell carbon (IASC), ground nut shell carbon (GSC), areca nut shell carbon (ASC), tamarind shell carbon (TSC) and cashew nut shell carbon (CSC) for the removal of Azure A (AA) dye from waste water. Different experimental parameters such as effect of initial concentration, contact time, dose, pH and particle size have been studied. The experimental results were analysed using Freundlich, Langmuir, Temkin, Redlich–Peterson and Dubinin–Radushkevich isotherm models. Different kinetic equations (first order, pseudo first order and pseudo second order) were applied to study the adsorption kinetics of AA on various activated carbons. Surface morphology of the adsorbents before and after adsorption is studied by Scanning Electron Microscopy (SEM). FT-IR studies revealed the presence of functional groups of dye on the adsorbents. It is inferred from the experimental result that the activated carbons (IASC, GSC, ASC, TSC and CSC) from agricultural wastes can be applied as an adsorbent substitute to commercial activated carbon (CAC) in the removal of AA dye from waste water.     

Adsorption of Safranin-T from wastewater using waste materials- activated carbon and activated rice husks

Textile effluents are major industrial polluters because of high color content, about 15% unfixed dyes and salts. The present paper is aimed to investigate and develop cheap adsorption methods for color removal from wastewater using waste materials activated carbon and activated rice husk-as adsorbents. The method was employed for the removal of Safranin-T and the influence of various factors such as adsorbent dose, adsorbate concentration, particle size, temperature, contact time, and pH was studied. The adsorption of the dye over both the adsorbents was found to follow Langmuir and Freundlich adsorption isotherm models. Based on these models, different useful thermodynamic parameters have been evaluated for both the adsorption processes. The adsorption of Safranin-T over activated carbon and activated rice husks follows first-order kinetics and the rate constants for the adsorption processes decrease with increase in temperature.     

Biosorption characteristics of uranium(VI) from aqueous solution by pummelo peel

The biomass pummelo peel was chosen as a biosorbent for removal of uranium(VI) from aqueous solution. The feasibility of adsorption of U(VI) by Pummelo peel was studied with batch adsorption experiments. The effects of contact time, biosorbent dosage and pH on adsorption capacity were investigated in detail. The pummelo peel exhibited the highest U(VI) sorption capacity 270.71?mg/g at an initial pH of 5.5, concentration of 50???g/mL, temperature 303?K and contacting time 7?h. The adsorption process of U(VI) was found to follow the pseudo-second-order kinetic equation. The adsorption isotherm study indicated that it followed both the Langmuir adsorption isotherm and the Freundlich adsorption isotherm. The thermodynamic parameters values calculated clearly indicated that the adsorption process was feasible, spontaneous and endothermic in nature. These properties show that the pummelo peel has potential application in the removal of the uranium(VI) from the radioactive waste water.     

Dye and its removal from aqueous solution by adsorption: A review

In this review article the authors presented up to-date development on the application of adsorption in the removal of dyes from aqueous solution. This review article provides extensive literature information about dyes, its classification and toxicity, various treatment methods, and dye adsorption characteristics by various adsorbents. One of the objectives of this review article is to organise the scattered available information on various aspects on a wide range of potentially effective adsorbents in the removal of dyes. Therefore, an extensive list of various adsorbents such as natural materials, waste materials from industry, agricultural by-products, and biomass based activated carbon in the removal of various dyes has been compiled here. Dye bearing waste treatment by adsorption using low cost alternative adsorbent is a demanding area as it has double benefits i.e. water treatment and waste management. Further, activated carbon from biomass has the advantage of offering an effected low cost replacement for non-renewable coal based granular activated carbon provided that they have similar or better adsorption on efficiency. The effectiveness of various adsorbents under different physico-chemical process parameters and their comparative adsorption capacity towards dye adsorption has also been presented. This review paper also includes the affective adsorption factors of dye such as solution pH, initial dye concentration, adsorbent dosage, and temperature. The applicability of various adsorption kinetic models and isotherm models for dye removal by wide range of adsorbents is also reported here. Conclusions have been drawn from the literature reviewed and few suggestions for future research are proposed.     

Utilization of Waste Biomass (Kitchen Waste) Hydrolysis Residue as Adsorbent for Dye Removal: Kinetic,Equilibrium, and Thermodynamic Studies

Kitchen waste hydrolysis residue (KWHR), which is produced in the bioproduction process from kitchen waste (KW), is usually wasted with potential threats to the environment. Herein, experiments were carried out to evaluate the potential of KWHR as adsorbent for dye (methylene blue, MB) removal from aqueous solution. The adsorbent was characterized using FT-IR and SEM. Adsorption results showed that the operating variables had great effects on the removal efficiency of MB. Kinetic study indicated pseudo-second-order model was suitable to describe the adsorption process. Afterwards, the equilibrium data were well fitted by using Langmuir isotherm model, suggesting a monolayer adsorption. The Langmuir monolayer adsorption capacity was calculated to be 110.13 mg/g, a level comparable to some other low-cost adsorbents. It was found that the adsorption process of MB onto KWHR was spontaneous and exothermic through the estimation of thermodynamic parameters. Thus, KWHR was of great potential to be an alternative adsorbent material to improve the utilization efficiency of bioresource (KW) and lower the cost of adsorbent for color treatment.     

Removal of Phenolic and Lignin Compounds from Bleached Kraft Mill Effluent by Fly Ash and Sepiolite

This study aimed to remove phenolic and lignin compounds from paper mill industry (4500 m³/h) wastewaters, which is discharged to sea from a plant located in the western Turkey. As adsorbent, fly ash, raw sepiolite and heat-activated sepiolite were used. The effect of factors such as, particle size, temperature and pH on adsorption process was investigated. From kinetic studies, equilibrium time was found as 1 h for both. The kinetic data supports pseudo-second order model but shows very poor fit for pseudo-first order model. Intraparticle model also shows that there are two separate stages in sorption process, namely, external diffusion and pore diffusion. Adsorption isotherms for fly ash and activated sepiolite were obtained at two different temperatures. From experiments carried out at different pHs, it was observed that pH plays an important role in the adsorption process in removing of both lignin and phenolic compounds, providing both ionizating the compounds and modifying sorbent surfaces. It was also observed that heat-activated sepiolite is more effective than raw sepiolite and fly ash to remove these compounds. Adsorption of lignin and phenolic compounds increases with decreasing particle size. In addition, the efficiency of adsorption decreases with increasing adsorption temperature for both fly ash and untreated sepiolite.     

Adsorption and desorption studies of a water soluble dye, Quinoline Yellow, using waste materials

Bottom ash, a power plant waste, and de-oiled soya, an agricultural waste material, were employed for the removal and recovery of Quinoline Yellow, a water-soluble dye. Characterization of adsorbent materials was made by their infrared and differential thermal analysis curves. Along with batch adsorption studies, which involve effect of pH, adsorbate concentration, sieve size, adsorbent dosage, contact time, temperature, etc., kinetic studies and column operations were also made to remove the dye from wastewater. On the basis of kinetic studies, specific rate constants involved in the processes were calculated and first-order adsorption kinetics was observed in both the cases. The paper also incorporates Langmuir and Freundlich adsorption isotherm models, which are used to calculate thermodynamic parameters and also to suggest a plausible mechanism of the ongoing adsorption processes. Fixed bed columns were prepared for both the adsorbents and bulk removal of the dye was achieved by eluting aqueous solution of the dye and saturation factor for both columns were evaluated. Dilute NaOH solution was then percolated through the exhausted columns to recover the adsorbed dye.     

Adsorption of naphthalene and pyrene from isooctane solutions on commercial activated carbons

The adsorption of naphthalene and pyrene on two different types of commercial activated carbons was studied by batch and column experiments. Adsorption equilibrium was measured at three different temperatures. Heats of adsorption were estimated from the equilibrium results and compared to other previous reports. From the column experiments, using parameters obtained from the batch experiments and literature correlations, effective surface diffusivities were estimated for naphthalene and pyrene on both adsorbents in different feed concentrations. The corrected diffusivities, using Darken equation, appear to be almost constant for naphthalene (ca. 1.3⋅10⁻⁸ cm²/min), and for pyrene (ca. 2.3⋅10⁻¹⁰ cm²/min), in both activated carbons.     

Adsorption studies on the removal of Vertigo Blue 49 and Orange DNA13 from aqueous solutions using carbon slurry developed from a waste material

Waste material (carbon slurry), from fuel oil-based generators, was used as adsorbent for the removal of two reactive dyes from synthetic textile wastewater. The study describes the results of batch experiments on removal of Vertigo Blue 49 and Orange DNA13 from synthetic textile wastewater onto activated carbon slurry. The utility of waste material in adsorbing reactive dyes from aqueous solutions has been studied as a function of contact time, temperature, pH, and initial dye concentrations by batch experiments. pH 7.0 was found suitable for maximum removal of Vertigo Blue 49 and Orange DNA13. Dye adsorption capacities of carbon slurry for the Vertigo Blue 49 and the Orange DNA13 were 11.57 and 4.54 mg g(-1) adsorbent, respectively. The adsorption isotherms for both dyes were better described by the Langmuir isotherm. Thermodynamic treatment of adsorption data showed an exothermic nature of adsorption with both dyes. The dye uptake process was found to follow second-order kinetics.     

Isotherm modelling and optimization of oil layer removal from surface water by organic acid activated plantain peels fiber

This research aimed to optimize and model the adsorption process of oil layer removal using activated plantain peels fiber (PPF), a biomass-based material. The adsorbent was activated by thermal and esterification methods using human and environmentally friendly organic acid. Effects of process parameters were examined by one factor at a time (OFAT) batch adsorption studies, revealing optimal conditions for oil removal. Also, RSM, ANN and ANFIS were used to adequately predict the oil removal with correlation coefficient > 0.98. RSM modelling revealed the best conditions as 90 °C, 0.2 mg/l, 1.5 g, 6 and 75 mins, for temperature, oil–water ratio, adsorbent dosage, pH and contact time respectively. Under these simulated conditions, the predicted oil removal was 96.88 %, which was experimentally validated as 97.44 %. Thermodynamic studies revealed the activation energy, change in enthalpy and change in entropy for irreversible pseudo-first order and pseudo-second order model as (15.82, 24.17, ?0.614 KJ/mols) and (33.21,40.31, ?0.106 KJ/mols) respectively, indicating non-spontaneous process; while modeling studies revealed that the adsorption process was highly matched to Langmuir’s isotherm, with maximum adsorption capacity of 50.34 mg/g. At the end of the overall statistical modelling, ANFIS performed marginally better than the ANN and RSM. It can be concluded from these results that our biomass-based material is an efficient, economically viable and sustainable adsorbent for oil removal, and has potentials for commercialization since the process of adsorption highly matched with standard models, and its capacity or percentage oil removal also compares favorably to that of commercially available adsorbents.     

Adsorbents from Waste materials

The possibility of using pyrolyzed wastes produced in already working incineration plants, as adsorbents for waste water treatment, was studied. Showing very poor adsorption properties, they were improved by steam activation technique used in the conventional activated carbon manufacturing. It is concluded that various organic waste materials can be converted to carbonaceous final products with a character similar to activated carbon. Their adsorption properties and pore size distribution are determined by the structure of the starting material. Although most of these samples have a low specific surface area, their pore volume is not negligible in the meso-and micropore range. Adsorption tests with model waste waters confirmed that adsorption properties are strongly influenced by the character of the suface. The adsorption capacity of these samples can be utilized for the treatment of strongly polluted industrial waste waters. Considering that the raw material ‘needed’ to manufacture these adsorbent is produced permanently and the adsorbents do not have to be regenerated, it might be worthwhile using these kinds of adsorbents in the primary treatment of industrial waste waters.     

Removal of boron from aqueous solution by clays and modified clays

In order to increase the adsorption capacities of bentonite, sepiolite, and illite for the removal of boron form aqueous solution, the clay samples were modified by nonylammonium chloride. Specific surface areas of the samples were determined as a result of N2 adsorption-desorption at 77 K using the BET method. X-ray powder diffraction analysis of the clays and modified clays was used to determine the effects of modifying agents on the layer structure of the clays. The surface characterization of clays and modified clay samples was conducted using the FTIR technique before and after the boron adsorption. For the optimization of the adsorption of boron on clays and modified clays, the effect of pH and ionic strength was examined. The results indicate that adsorption of boron can be achieved by regulating pH values in the range of 8-10 and high ionic strength. In order to find the adsorption characteristics, Langmuir, Freundlich, and Dubinin-Radushkevich adsorption isotherms were applied to the adsorption data. The data were well described by Freundlich and Dubinin-Radushkevich adsorption isotherms while the fit of Langmuir equation to adsorption data was poor. It was reached that modification of bentonite and illite with nonylammonium chloride increased the adsorption capacity for boron sorption from aqueous solution.