Alternative Low-cost Adsorbent Research Articles

Batch Adsorption of Safranin Dye from an Aqueous Solution of Balanites aegyptiaca Seed Coats

This study was aimed at using Balanite aegyptiaca seed coats activated carbon (BAAC) as a potential adsorbent to remove safranin dye from aqueous solution. BAAC was prepared from Balanite aegyptiaca seed coats using a one-step procedure with 67.27% yield, 3.23% ash content, 695 m2/g surface area and 203 mg/g iodine number. The FTIR spectroscopy revealed O-H, N-H, C-H, C=C, C-O-H stretching vibrations. The influences of agitation time, initial dye concentration and adsorbent dose were studied in batch experiments at room temperature. The adsorptions were rapid at the first 15 minutes of agitation, with the uptake of 2.746 mg/kg. The adsorption equilibrium was achieved at 90 minutes of agitation. Kinetic studies showed good correlation coefficient for both pseudo-first order and pseudo-second-order kinetics model but fitted well into pseudo-second order kinetic model. The adsorption data fitted well into Langmuir isotherm with correlation coefficient (R2) very close to unity and Langmuir maximum adsorption constant, qm 1.00. Thus, the fitting into Langmuir indicates monolayer coverage on the adsorbents. The results showed that BAAC has the potential to be applied as alternative low-cost adsorbents in the remediation of dye contamination in wastewater.

Equilibrium, Kinetics, and Thermodynamic Studies of Malachite Green Adsorption onto Fig (Ficus cartia) Leaves.

The release of dyes from dying industries such as leather, paper, and textiles is an important cause of environmental pollution. In the present study, the batch adsorption measurements were carried out using stimulated aqueous solutions and the effect of operating variables such as initial malachite green concentration, amount of adsorbent, solution pH, contact time, and solution temperature, were investigated. The experimental result showed that the percentage removal decreased with an increase in initial dye concentration but increased as pH of the solution, contact time, and adsorbent dose increased. The equilibrium data were analyzed using Langmuir adsorption isotherm, Freundlich adsorption isotherm, and Tempkin isotherm models, and it was observed that the Langmuir adsorption isotherm better described the adsorption process. The monolayer adsorption capacity of activated carbon prepared from fig leaves for malachite green adsorption was found to be 51.79 mg/g at 298 K. Furthermore, the adsorption kinetics of the dye was investigated, and the rate of adsorption was found to follow the pseudo-first-order kinetic model with intraparticle diffusion as one of the rate-determining steps. The negative value of ΔG0 and the positive values of ΔH0 indicate the spontaneous and endothermic nature of the adsorption process, respectively. The experimental result obtained in the present study and comparison with other reported adsorbents indicate that activated carbon prepared from fig leaves could be used as a low-cost alternative adsorbent for the removal of malachite green from aqueous solution.

Kinetic Modeling and Thermodynamic Study of Methylene Blue Sorption on Bael Activated Carbon

This work presents methylene blue (MB) removal by bael shell activated carbon (BSAC) from simulated wastewater. The effects of various parameters such as pH, contact time, initial MB concentration and temperature were investigated. The adsorption capacity was found to increase with increase in the four parameters studied. Equilibrium data were fitted with both Langmuir as well as Freundlich adsorption model. The equilibrium data were best represented by the Langmuir isotherm, with maximum monolayer sorption capacity of 196.08 mg/g at 30 oC. The sorption kinetics was found to follow the pseudo-second-order kinetic model. SEM and EDX analysis were employed to analyse the morphology and elemental composition of adsorbent. FT-IR spectra of BSAC showed that the OH- functional group was predominantly responsible for the MB adsorption. The results revealed that BSAC can be an attractive low cost alternative adsorbent for the treatment of wastewater containing higher concentrations of MB.

Removal of methyl orange over low-cost silica nanoparticles extrated from bamboo leaves ash

Bamboo leave were used to generate silica nanoparticles (SNPs) and undergo modification to form mesoporous silica nanoparticles (MSNs), and examine its ability to adsorb methyl orange (MO). Two types of silica been approached in observation to removed MO. Mesoporous silica nanoparticles water based (MSN-w) and silica bare be compared to determine the high efficiency of removal rate respectively. Parameter such pH solution of dyes been investigate in order to identify a suitable and optimum pH to eliminate MO from water bodies. MO can be metabolized into the aromatic compound of amines by intestinal microorganisms. MO are the one of the compound that categorized in stable compound with shows a very low of biodegradability and its dissolved in water contact but have a high percentage of difficulty to eliminate from water bodies by using treatment such as purification process of water within industry or by treatment methods. Through these studies, the suitable pH for the removal MO were found pH 3 using 0.4 g/L of adsorbent dosage with a rapid removal about 92.48% for MSN-w and 83.88% for silica bare. An excellent performance of MSN-w shows it could be potential to be applied as alternative low-cost adsorbent in the remediation of organic contamination in wastewater.

An alternative method of removing Cr (VI) from aquatic solution using chemically modified cone biomass and Fomitopsis pinicola

We report the adsorption of Cr (VI) ions from aqueous solution by forest waste. Two adsorbents were prepared from cone biomass and Fomitopsis pinicola. To study the kinetics of both were used three particular size (<0.5, 0.5-1, 1-2 mm). It was found that adsorbents chemically modified with a HCl (activation 2mol/L, activated for 60 min) demonstrated better Cr(VI) removal capabilities as compared to pure adsorbents in terms of their adsorption rate. The optimum conditions for removal of Cr(VI) were found to be particular size <0,5 mm, pH=1, contact time 10 min, adsorbent dosage 20g/L, concentration of Cr(VI) 100 mg/L, temperature 25 ± 1°C, rpm 200. The percent removal at these optimum conditions was found to be 100 % for both biosorbents. The Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The maximum uptake capacities for 40.98 mg/g and 45.05 mg/g for cone biomass and Fomitopsis pinicola, respectively. To study the effect of other ions on the Cr (VI) removal by both biosorbents, electroplating industry wastewater was collected from an industry. Overall, the experimental results suggest that cone biomass and Fomitopsis pinicola could be used as low cost alternative adsorbents for the treatment of low concentration Cr (VI) containing wastewater.

Soils Developed from Dolomitic Shale in the Yichang Area, China and Adsorption Characteristics for Phenol

Recently, the problem of phenolic organics pollution has become increasingly serious. More and more strategies have been developed to remove phenolic organics from water, including oxidation, adsorption, chemical precipitation, etc. Among them, adsorption technology has attracted great attention due to its advantages of high efficiency, simplicity and easy operation. In this study, the natural shale soil without any modification was directly used as adsorbent to remove phenol from aqueous solutions. The shale soil samples were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and nitrogen adsorption-desorption isotherms. Detailed kinetics and isotherm studies of phenol adsorption onto shale were investigated. According to the results of the orthogonal test, the influence degree of the four factors on the removal of phenol by soil samples was operating temperature > adsorbent dosage > contact time > pH. The adsorption kinetics of phenols by the soil corresponded with the pseudo-second-order kinetic model. Thermodynamic studies indicated that Freundlich adsorption isotherm model could better describe phenol removal characteristics than Langmuir adsorption isotherm model. And the maximum adsorption capacity was found to be 9.68 mg/g for phenol. It is concluded that shale soil without any modification or activated methods could be employed as a low-cost alternative adsorbent for wastewater treatment.

Single-component and competitive adsorption of tetracycline and Zn(ii) on an NH4Cl-induced magnetic ultra-fine buckwheat peel powder biochar from water: studies on the kinetics, isotherms, and mechanism.

Single-component and competitive adsorption of tetracycline (TC) and Zn(ii) on an NH4Cl-induced magnetic ultra-fine buckwheat peel powder biochar (NH4Cl-BHP-char/Fe3O4) was investigated in batch experiments. NH4Cl-BHP-char/Fe3O4 exhibited a large surface area of 1119.097 m2 g−1 and a total pore volume of 0.139 cm3 g−1 and was easily separated from aqueous solution using a magnet. Also, adsorption was endothermic, spontaneous, and highly pH-dependent. The optimum pH of the single-component adsorption of TC and Zn(ii) was 4.0 and 6.5, respectively, and the optimum pH of co-adsorption was 6.0. The kinetics studies showed the prepared biochar could be rapidly adsorbed within 60 min, and chemical adsorption was dominant. For single-component adsorption, the maximum adsorption capacities of TC and Zn(ii) were 106.38 and 151.52 mg g−1, respectively, and they underwent monolayer adsorption on the biochar surface. Moreover, for competitive adsorption, maximum TC and Zn(ii) adsorption capacities of 126.58 and 357.14 mg g−1 were achieved. Both film diffusion and intra-particle diffusion were found to be significant processes to facilitate adsorption. TC and Zn(ii) promoted the adsorption of each other. The proposed biochar could be used repeatedly for at least four cycles. All these results demonstrated that developed NH4Cl-BHP-char/Fe3O4 was regarded as a low-cost alternative adsorbent to remove the heavy metal ions and antibiotic pollutants from water or wastewater.

Adsorption and Removal of Methylene Blue from Aqueous Solution Using Sterile Bract of Araucaria angustifolia as Novel Natural Adsorbent

The aim of this work was to study the adsorption and removal of methylene blue from aqueous solution using sterile bract of Araucaria angustifolia as novel natural adsorbent. Raw and boiling-treated sterile bract samples were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, and point of zero charge. The contents of humidity, ash, total extractive content, lignin and cellulose were 13.20, 3.30, 7.12, 44.45 and 30.92%, respectively. The methylene blue adsorption mechanism in the sterile bract was evaluated using non-linear Langmuir, Freundlich, Redlich–Peterson and Sips isotherm models, whereas the adsorption kinetic was evaluated using pseudo-first- and pseudo-second-order kinetic models. The methylene blue removal efficiencies of the raw and boiling-treated bracts were 98.59 ± 0.01 and 99.90 ± 0.01%, respectively, after 480 min. The best adsorption efficiency was found within 480 min of contact, 5.0 g of adsorbent with 500 mesh granulometry, pH = 6, initial adsorbate concentration of 150 mg L−1 and temperature of 292 K. The maximum methylene blue adsorption capacities of the raw and boiling-treated bracts according to the non-linear Langmuir isotherm model were 125.34 and 138.65 mg dye per gram bract, respectively. The kinetic fit depends on the solution pH, determination coefficient and Chi square test statistic. From thermodynamic results, it was concluded that the adsorption process is favorable, spontaneous (ΔG 0). Overall, the sterile bract of Araucaria angustifolia could be applied as low-cost alternative adsorbent for the treatment of textile industry wastewater.

Removal of Cr(VI) from water using pineapple peel derived biochars: Adsorption potential and re-usability assessment

In the present study, biochar was prepared using waste pineapple peel biomass with slow pyrolysis at 350, 450, 550 and 650°C to explore the effect of temperature treatment on characteristic properties of biochars. Various characterization parameters were analyzed to elucidate the temperature driven changes. Pyrolysis temperature had a significant impact on the properties of the developed biochar, leading to morphological and physiochemical changes. The relationship between pyrolysis temperature and induced physicochemical properties with Cr(VI) adsorption onto biochars was also investigated. Various adsorption parameters as pH (1.5–8), initial Cr(VI) concentration (10–500mg/L), biochar dose (0.5–10g/L) and adsorption time (0–96h) were studied. Freundlich isotherm (R2=0.957–0.972) and pseudo-second-order kinetics model (R2=0.981–0.994) best fitted the experimental data suggesting multilayer adsorption with chemical interactions between Cr(VI) ions and biochar surface. Biochar prepared at 350°C was found to have the highest adsorption capacity of 41.67mg/g among biochars. Complete Cr(VI) removal was achieved at 10mg/L Cr(VI) concentration with all the biochars. Rather than surface area polarity of biochar was found to be the influencing character of biochar for Cr(VI) adsorption. Feasibility of produced biochars for reuse was also explored. The study suggested that pineapple peel residue can be recycled to biochars with high carbon stability and can be used as a low-cost alternative adsorbent for wastewater treatment.

Adsorption performance and mechanism of a low-cost biosorbent from spent seedcake of Calophyllum inophyllum in simultaneous cleanup of potentially toxic metals from industrial wastewater

Among the contaminants that are frequently associated with industrial wastewaters, potentially toxic metals are of great health concern because they are non-biodegradable and can be transformed by biochemical processes to more poisonous metal-organic complexes. Thus, safe and adequate disposal of wastewater containing these metals into the environment remains a front-burner challenge. This study investigated metal ions removal from wastewaters using adsorbents generated from the Spent Seedcake of Calophyllum inophyllum (SSCI) as an alternative low-cost adsorbent. Batch adsorption process was employed to demonstrate the adsorption capacity for the multi-component removal of Pb(II), Cd(II) and Zn(II) at optimized experimental conditions. Carbonization and microwaving of the biosorbent produced an optimal performance for the uptake of the metals at solution pH of 9, temperature of 30 °C, dosage, 10 g/L and 60 min equilibrium time. The maximum adsorption capacities of the biosorbent were 52.63, 51.28 and 17.99 mg/g for Pb2+, Cd2+and Zn2+ respectively. The adsorption kinetics of the metals unto the biosorbent was adequately described by a pseudo-second-order kinetic model with positive enthalpy (ΔH) indicating the endothermic nature of the adsorption process while the negative values of the Gibbs free energy (ΔG) confirmed the spontaneity of the adsorption process for all the metals studied.The effectiveness of the biosorbent was tested with real wastewater samples and a removal of the metals between 55–71% was achieved.

The Efficiency of Cactus Leaves and Wood Charcoal as a Potential Low-Cost Adsorbent for Removal of Toxic Heavy Metals from Industrial Effluents

Presence of toxic heavy metals in the environment is of great concern due to their persistence in nature and chronic adverse effects on human health and the environment. Present paper tries to evaluate the efficiency of cactus leaves ( Opuntia f. indica ) and activated carbon made from acacia etbiaca as an adsorbent for the removal of heavy metal pollutants such as cadmium, lead and chromium from water. Adsorption properties such as size, dose, initial concentration and time of contact for cadmium, lead and chromium were studied through batch method. Before removing the toxic heavy metals (Cd, Pb and Cr), the fresh unpeeled cactus leaves (adsorbent) and activated carbon were washed with distilled water to eliminate the turbidity and smell from fresh unpeeled cactus. To describe the equilibrium isotherms, the experimental data were analyzed by the Langmuir and Freundlich isotherm models. Thus, the Freundlich model gave the best correlation with the experimental data. Therefore, the findings indicated that the cactus and activated carbon made locally from acacia etbiaca were found to be effective and low-cost alternative adsorbents for the removal of toxic heavy metals from industrial effluents. The preparation method allowed the use of these materials by local industries for effective remediation of pollution by removing heavy metals from their effluents. Keywords : Cactus leaves; Acacia etbiaca ; Heavy metals; Adsorption, Industrial effluents; Water purification.

Removal of Lead (II) Ions from Aqueous Solution Using Desiccated Coconut Waste as Low-Cost Adsorbent

Waste from coconut milk processing industry namely desiccated coconut waste (DCW) was used to remove Pb (II) due to Pb (II) hazardous effect in the environment. The main objective of this study is to study and develop the adsorption capability of the DCW adsorbent. The chemical and physical properties of the DCW adsorbent were depicted by the FT-IR spectra and the elemental CHNS analysis. The maximum Pb (II) adsorption capacity (Q) toward DCW adsorbent was 50.33 mg/g at pH solution of 6 with the rate of 0.004 mg/min. In addition, the Pb (II) equilibrium data were best fitted to the Langmuir isotherm model, whereas the kinetic data obeyed the pseudo-second-order kinetic model. In the regeneration study, DCW adsorbent has remained stable up to two adsorption cycles. Thus, these satisfactory results revealed that the use of DCW as an alternative low-cost adsorbent for the removal Pb (II) from aqueous solution is feasible.

Removal of Cr(VI) from synthetic wastewater by adsorption onto coffee ground and mixed waste tea

We attempted to recycle mixed waste tea and coffee ground as alternative low-cost adsorbents for Cr(VI) removal. The adsorption parameters optimized were: initial Cr(VI) concentration (10–30 mg L−1), contact time (180 min), adsorbent dose (2.0 g L−1), initial pH (2.0), temperature (30–50 °C), and agitation speed (250 rpm). Freundlich isotherm was found better fitted with a high correlation coefficient (R2 = 0.97 for mixed waste tea and 0.92 for coffee ground) than to Langmuir model (R2 = 0.89 for mixed waste tea and 0.86 for coffee ground) for the 10–250 mg L−1 concentration range. Analysis of kinetic studies indicated that Cr(VI) adsorption by both adsorbents was consistent with the pseudo-second-order kinetic model with a good R2 and Marquardt's present standard deviation (MPSD) values. Experimental data demonstrated a sorption capacity of 94.34 mg g−1 of mixed waste tea and 87.72 mg g−1 of coffee ground. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Energy dispersive X-ray spectroscopy (EDS) revealed the noticeable chromium accumulation on the adsorbent surfaces after adsorption. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) studies showed that carbon and oxygen functional groups on the surface of both adsorbents involved in Cr(VI) adsorption. The adsorbents could be reused four times. Large-scale operation using 100 L of packed-bed reactor showed the breakthrough time of adsorption for mixed waste tea of 30 min in 100 mg L−1 Cr(VI) concentration. These results suggested that mixed waste tea and coffee ground be considered as alternative adsorbent for Cr(VI) removal.

Utilization of Empty Fruit Bunch Fibre as Potential Adsorbent for Ammonia Nitrogen Removal in Natural Rubber Wastewater

The objective of this study was to identify the performance of empty fruit bunch (EFB) to assess its use as potential adsorbent in treat ammonia nitrogen in natural rubber wastewater. The adsorption method was employed to investigate the effect of a number of factors, namely, adsorbent dosage, pH, shaking speed and contact time. The results revealed that the removal of ammonia nitrogen up to 79.5% from natural rubber wastewater. The adsorption efficiency of EFB fibre was maximum at 3.5 g dosage, pH 7, 150 rpm shaking speed and 120 min contact time. The results proved that EFB fiber are good alternative low cost adsorbent for the removal of ammonia nitrogen from natural rubber wastewater. The Langmuir isotherm (R2=0.9923) described ammonia nitrogen adsorption slightly better than the Freundlich isotherm (R2 = 0.9450), suggesting a monolayer adsorption behaviour of the adsorption processes.

Synthesis of porous pig bone char as adsorbent for removal of DBP precursors from surface water.

This research study aims to investigate the efficiency of synthesized porous pig bone char (PBC) for reduction of disinfection by-product (DBP) precursors from surface water. Dissolved organic matter (DOM) is commonly present in natural water and acts as a disinfection by-product precursor. Adsorption is one of the promising technologies that is commonly applied for DOM removal. Interestingly, the properties of pig bone are such that it has a surface area and pore volumes that can adsorb DOM. Pig bone was synthesized as porous bone char (PBC). The results show that synthesized PBC at 900 °C (PBC-900 °C) provides a high volume of mesoporous structure. The adsorption process was best fitted with the pseudo-second-order and Freundlich isotherm model. Thus, the mechanisms occurred on the multilayer adsorption of the surface. PBC-900 °C can remove approximately 70-80% of DOM with varying concentrations, from 0.2 g/L to 0.8 g/L. Furthermore, the results of fluorescence excitation-emission (FEEM) showed that humic acids and humic-like substances in water can be removed by using PBC at concentrations higher than 0.4 g/L. From the obtained results, it can be concluded that PBC is an alternative low-cost adsorbent which can be utilized for reduction of DBP precursors from water.

Thermal and thermal-acid treated sewage sludge for the removal of dye reactive Red 120: Characteristics, kinetics, isotherms, thermodynamics and response surface methodology design

Sludge from wastewater treatment plant was used as low-cost adsorbent to remove the dye Reactive Red 120 (RR 120) from an aqueous solution. Adsorbents were prepared through thermal (pyrolysis) and chemical treatment (functionalization with HNO3) of sewage sludge. Adsorbents were characterized through physical-chemical and textural analyses. The mesoporous nature of pyrolyzed sludge (PS) and functionalized slugde (FS) influenced the adsorption of RR 120. Moreover, adsorbents surface was rich mainly in carboxylic groups. Batch kinetic experiments were conducted on the statistical design elaborated with central composite rotational design under different pH (3.5–11.5) and temperature (30 °C–60 °C) to achieve the best operational conditions. The response surface methodology (RSM) indicated optimal dye removal efficiency above 94% and 98% at pH and temperature pairs of 3.5/60 °C and 5.4/60 °C for PS and FS, respectively. Kinetics data revealed that pseudo-second-order model better described the adsorption with 2.46 mg g−1 at pH 3.5 for PF and 2.61 mg g−1 at pH 5.4 for FS. Langmuir isotherm model was the best fitted to the adsorption equilibrium data with monolayer maximum adsorption capacities of 14.69 mg g−1 for PS and 46.81 mg g−1 for FS at optimal conditions. The positive ΔH° results indicated an endothermic process (4.73 kJ mol−1 and 8.02 kJ mol−1). Thus, it was concluded that the sewage sludge can be used as an alternative low-cost adsorbent in the removal of RR 120.

Modified oil shale ash and oil shale ash zeolite for the removal of Cd2+ ion from aqueous solutions

ABSTRACTThe present study attempted to prepare modified oil shale ash and oil shale ash zeolite from oil shale ash, which were characterized by X-ray diffraction, scanning electron microscopy, and N2 adsorption–desorption. Detailed kinetics and isotherm studies of Cd2+ adsorption onto modified oil shale ash and oil shale ash zeolite were examined. The adsorption capacity was determined as a function for the adsorption system. The results showed that the adsorption capacity of oil shale ash zeolite was higher compared to modified oil shale ash and that the time required to reach equilibrium was shorter. The kinetics studies showed that Cd2+ adsorption was well fit by the pseudo-second-order kinetics model. Both the Langmuir and the Freundlich isotherms described the adsorption data well. And the maximum monolayer adsorption capacity determined by the Langmuir adsorption isotherm was found to be 108.70 and 169.49 mg/g for Cd2+ adsorption onto modified oil shale ash and oil shale ash zeolite, respectively. It was concluded that Cd2+ in aqueous solutions was more efficiently removed by oil shale ash zeolite, which could be employed as a low-cost and effective alternative adsorbent for wastewater treatment than modified oil shale ash.

An alternative low-cost adsorbent for gold recovery from cyanide-leached liquors: Adsorption isotherm and kinetic studies

Pristine Macadamia nutshell-based activated carbons were chemically oxidized with different concentrations of H3PO4 and HNO3 to increase their surface adsorption properties and further explore if they could be an attractive alternative low-cost adsorbent for gold recovery from cyanide-leached liquors. The modified activated carbons were labeled MACN20, MACN40 and MACN55 to signify the materials prepared from 20%, 40% and 55% (v/v) HNO3, respectively. Similar nomenclature was followed for H3PO4-modified activated carbons. Brunauer-Emmet-Teller, scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, elemental analysis and X-ray diffraction spectroscopy were used to characterize the prepared activated carbons. The physical properties were attained through determining attrition, ash content, volatile matter and moisture content of all the activated carbons. Various parameters that affect selective adsorption such as the effect of initial concentration, time, agitation speed, interfering species and the dose of the adsorbent were investigated. Optimal parameters for gold ion adsorption were as follows: solution pH, 10; contact time, 6 h; agitation speed, 150 r/min; sorbent amount, 4 g and initial concentration, 5.5 mg/L. The observed selectivity order was not the same for all the adsorbents, but the adsorption of gold was found to be mostly influenced in the presence of nickel and least influenced by copper. MACN55 was found to be the most efficient adsorbent with 74% of gold adsorption from a real-world sample and displayed a similar performance to coconut-based activated carbons.

A Review on Heavy Metal Ions and Dye Adsorption from Water by Agricultural Solid Waste Adsorbents

Agricultural solid wastes either in natural or in modified forms have been successfully used for decades as non-conventional cost-effective adsorbents for removing metal ions and dyes from their aqueous phase and have been recognized as a sustainable solution for wastewater treatment. Therefore, this review article provides extensive literature information about heavy metals and dyes, their classifications and toxicity, various treatment methods with emphasis on adsorption characteristics by numerous agricultural solid wastes, or agricultural solid waste-derived adsorbents under various physicochemical process conditions. This review article not only provided an up-to-date information on the application of sustainable low-cost alternative adsorbents such as agricultural solid wastes, agricultural by-products, and biomass-based cost-effective activated carbon and various other natural materials in the batch adsorptive removal of heavy metal and dye from aqueous phase but also presented a comprehensive compilation of adsorptive pollutant removal information based on various reported continuous column operation studies which is one of the new aspect to this review article. The effectiveness of various batch and column operational process parameters on mechanistic adsorptive removal of both heavy metals and dyes by various agricultural solid waste-based adsorbents has been critically discussed here. Batch and column adsorption mechanism, batch kinetics, column dynamic modeling, and adsorptive behavior of adsorbents under various process parameters have also been critically analyzed and compared. Finally, literature information on recovery and regeneration through desorption techniques and cost comparison of various agricultural solid waste adsorbents with commercial activated carbons have also been reported here. Conclusions have been drawn from the literature reviewed, and few suggestions for future research direction are proposed.

Removal of textile dyes from aqueous solutions using low cost Moroccan clay

This study aims to evaluate the technical feasibility to apply natural clay from Fez area as a low cost alternative adsorbent to remove dyes from contaminated waters. Methylene blue (MB) and congo red (CR) are used here as representatives of cationic and anionic dyes normally present in wastewater from textile industry. This material was characterised by different physical-chemical methods, including BET, X-ray fluorescence and pHPZC. Additionally, the influence of operating conditions such as contact time, adsorbent dosages and pH were evaluated. Experimental results show that the adsorption processes takes place very rapid, reaching the equilibrium at 30 and 45 min for MB and CR, respectively. Maximum adsorption capacities result to be pH-depends. Hence, MB adsorption is favoured under basic pH conditions, whereas CR does it at acid pH. A pseudo-second-order kinetic model provides the best fit to the experimental data of MB and CR adsorption. Adsorption data are better described by Langmuir and Toth isotherm models. Adsorption occurs with a maximum monolayer adsorption capacity of 195 and 185 mg g-1 for MB and CR, respectively. Experimental results indicate that the Moroccan clay could be used as a potential adsorbent for the elimination of dyes from contaminated waters, at a lower cost.