Tushar Kanti Sen

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.

The performance enhancements of upflow anaerobic sludge blanket (UASB) reactors for domestic sludge treatment – A State-of-the-art review

Nowadays, carbon emission and therefore carbon footprint of water utilities is an important issue. In this respect, we should consider the opportunities to reduce carbon footprint for small and large wastewater treatment plants. The use of anaerobic rather than aerobic treatment processes would achieve this aim because no aeration is required and the generation of methane can be used within the plant. High-rate anaerobic digesters receive great interests due to their high loading capacity and low sludge production. Among them, the upflow anaerobic sludge blanket (UASB) reactors have been most widely used. However, there are still unresolved issues inhibiting the widespread of this technology in developing countries or countries with climate temperature fluctuations (such as subtropical regions). A large number of studies have been carried out in order to enhance the performance of UASB reactors but there is a lack of updated documentation. In face of the existing limitations and the increasing importance of this technology, the authors present an up-to-date review on the performance enhancements of UASB reactors over the last decade. The important aspects of this article are: (i) enhancing the start-up and granulation in UASB reactors, (ii) coupling with post-treatment unit to overcome the temperature constraint, and (iii) improving the removal efficiencies of the organic matter, nutrients and pathogens in the final effluent. Finally the authors have highlighted future research direction based on their critical analysis.

Metal ion removal from aqueous solution using physic seed hull

The potential of physic seed hull (PSH), Jantropha curcas L. as an adsorbent for the removal of Cd(2+) and Zn(2+) metal ions from aqueous solution has been investigated. It has been found that the amount of adsorption for both Cd(2+) and Zn(2+) increased with the increase in initial metal ions concentration, contact time, temperature, adsorbent dosage and the solution pH (in acidic range), but decreased with the increase in the particle size of the adsorbent. The adsorption process for both metal ions on PSH consists of three stages-a rapid initial adsorption followed by a period of slower uptake of metal ions and virtually no uptake at the final stage. The kinetics of metal ions adsorption on PSH followed a pseudo-second-order model. The adsorption equilibrium data were fitted in the three adsorption isotherms-Freundlich, Langmuir and Dubinin-Radushkevich isotherms. The data best fit in the Langmuir isotherm indication monolayer chemisorption of the metal ions. The adsorption capacity of PSH for both Zn(2+) and Cd(2+) was found to be comparable with other available adsorbents. About 36-47% of the adsorbed metal could be leached out of the loaded PSH using 0.1M HCl as the eluting medium.

Adsorption of methylene blue dye from aqueous solution by novel biomass Eucalyptus sheathiana bark: equilibrium, kinetics, thermodynamics and mechanism

AbstractThis study was undertaken to evaluate the adsorption potential of a naturally available, cost-effective, raw eucalyptus bark (EB) (Eucalyptus sheathiana) biomass, to remove organic methylene blue (MB) dye from its aqueous solutions. Effects of various process parameters such as initial dye concentration, adsorbent loading, solution pH, temperature, presence of salts, mixture of dyes and surfactant onto MB dye adsorption by bark material were studied. Significant effect on adsorption was witnessed on varying the pH of the MB solutions. Results showed that the optimum pH lies between 7.4 and 10.0. The extent (%) of MB adsorption from aqueous solution decreased with the increase in the initial MB dye concentration, but increased with rise in temperature. The extent of MB dye adsorption was found to be enhanced due to increase of salts concentration. This is because of salting-out-effect, which comprises the changes of various short range forces. The overall kinetic studies showed that the MB dye adso...

Synthesis and characterization of slow pyrolysis pine cone bio-char in the removal of organic and inorganic pollutants from aqueous solution by adsorption: Kinetic, equilibrium, mechanism and thermodynamic

Pine cone bio-char was synthesized through slow pyrolysis at 500°C, characterized and used as an effective adsorbent in the removal of organic Methylene Blue (MB) dye and inorganic nickel metal (Ni(II) ions from aqueous phase. Batch adsorption kinetic study was carried out by varying solution pH, dye concentration, temperature, adsorbent dose and contact time. Kinetic and isotherm models indicates that the adsorption of both adsorbates onto pine cone bio-char were mainly by chemisorption. Langmuir maximum adsorption capability was found to be 106.4 and 117.7mg/g for Methylene Blue (MB) and nickel ions (NI(II) respectively. Thermodynamic parameters suggested that the adsorption was an endothermic and spontaneous. These results indicate the applicability of pine cone as a cheap precursor for the sustainable production of cost-effective and environmental friendly bio-char adsorbent.

Fixed-bed dynamic column adsorption study of methylene blue (MB) onto pine cone

AbstractThe effectiveness of pine cone biomass in the removal of methylene blue (MB) dye from its aqueous solution was tested here by a fixed-bed column adsorption study. The adsorption column breakthrough curves (BTCs) indicated the favourable column dynamics and its dye adsorptive behaviour depends on feed flow rate, initial MB dye concentration and column bed height. The results showed that the amount of total sorbed dye, equilibrium dye uptake, mass transfer zone and total percentage of dye removal increased with increase in MB dye concentration and the height of the bed, but decreased with increase in initial flow rate. To determine the fixed-bed column adsorption kinetic parameters, Thomas, Yoon–Nelson and Bed Depth Service Time (BDST) models fitted the experimental BTC obtained from dynamic studies. All these parameters are required for the design of adsorption column and it was found that all three kinetic models were applicable. Thomas model showed that the value of maximum solid-phase concentrat...

Removal of anionic surfactant sodium dodecyl sulphate from aqueous solution by adsorption onto pine cone biomass of Pinus Radiate: equilibrium, thermodynamic, kinetics, mechanism and process design

Abstract This study was undertaken to evaluate the adsorption potential of a natural, low-cost agricultural by-product adsorbent, Pine cone (Pinus Radiate), to remove sodium dodecylsulfate (SDS) from aqueous solution. It was found that the extent of SDS adsorption by pine cone biomass increased with initial surfactant concentration and contact time but decreased with increasing solution pH, amount of adsorbent, and temperature of the system. These studies also suggested that the electrostatic forces and surfactant self-assembly are dominant mechanisms governing this pH dependent adsorption process. Overall, kinetic studies showed that the surfactant adsorption process followed pseudo-second-order kinetics based on pseudo-first-order and intraparticle diffusion models. The different kinetic parameters including rate constant, half adsorption time, and diffusion coefficient were determined at different physicochemical conditions. Equilibrium data were fitted by both the Langmuir isotherm and Freundlich adso...

Impact of various physico-chemical parameters on spontaneous nucleation of struvite (MgNH4PO4.6H2O) formation in a wastewater treatment plant: kinetic and nucleation mechanism

AbstractIn this study, the effect of various physico-chemical parameters such as supersaturation, temperature and pH, and the presence of foreign ion on the nucleation of struvite formation in a wastewater treatment plant were studied experimentally. Mechanism of nucleation kinetics of struvite (MgNH4PO4.6H2O) formation has been identified by thermodynamic parameters study. The time taken for nucleation to occur (often indicated by the induction time) is a measure of struvite nucleation. It was found that induction time decreased with an increase in supersaturation, temperature and pH but increased with the presence of excess chloride (Cl−) ion. Interfacial energy of two nucleation mechanisms (γs,hom and γs,het), homogeneous and heterogeneous, increased with an increase in solution pH for all temperatures whereas interfacial energy of crystals increased with decrease in temperature. Thermodynamic parameters such as activation energy and interfacial energy were calculated based on rate of nucleation for bo...

Dewaterability of Anaerobic Digested Sludge with Cations and Chitosan as Dual Conditioners

Anaerobic digested sludge dewatering is very important in sludge management and disposal. In this study, flocculation and dewatering behaviour of anaerobic digested sludge were investigated using metal cations (sodium, magnesium, calcium, ferric and aluminium salts) and chitosan as dual conditioners. The trivalent ferric and aluminium ions were found to be more effective than the monovalent and divalent cations in improving sludge dewaterability as measured by capillary suction time (CST). Post-addition of chitosan into the sludge pre-coagulated with metal cations further enhanced the sludge dewaterability. This study suggests that pre-destabilisation of sludge by coagulation with metal cations followed by chitosan addition as polymeric flocculant may improve the dewaterability of anaerobic digested sludge.

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.