There are number of water purification techniques but the adsorption is one of the most simplest, effective and economical method for wastewater purification. In this article a large number of solid adsorbents such as Natural adsorbents, Agricultural Wastes, Industrial wastes, Biomass, Nanoadsorbents: Carbon based nanomaterials, Nobel metal based nanomaterials, Metal oxide based nanomaterials, Spinel ferrite based nanomaterials, Nanocomposites, Dendritic polymers; Geopolymer cement have been discussed for the removal of different pollutants from waste water. Removal of Fluoride, Phosphate, Nitrate and Radionuclides from wastewater has also been reviewed in this article. Adsorption isotherm models, kinetic models, thermodynamic parameters and adsorption mechanism have also been discussed. The present article lists different type of adsorbents and reviews state-of-the-art of the removal of different pollutants from water. The efforts have been made to discuss the sources of contamination and toxicities of pollutants. Adsorption mechanisms responsible for pollutants removal by different adsorbents have been reviewed. Attempts have also been made to point out the advantages and drawbacks of adsorbents and the future research needs in the area of water purification by adsorbents.

Water purification by using Adsorbents: A Review

A review on agro-industrial waste (AIW) derived adsorbents for water and wastewater treatment.

Batch adsorption experiment of malachite green (MG) was studied with walnut shell (WS). Adsorption of MG onto WS was confirmed by FTIR analysis. Particle size, dosage, effect of dye concentration, pH, temperature and ionic strength were investigated. The optimized conditions for adsorption process in this study was carried out using WS of dosage 0.03 g/20 mL dye, at room temperature, ambient pH and agitation rate of 250 rpm for 2 h. The kinetics of the adsorption process was studied using four models: Lagergren 1st order, pseudo 2nd order, Weber–Morris intraparticle diffusion and the Boyd models. Kinetics data is best fitted with pseudo 2nd order. Weber–Morris model showed that intraparticle diffusion may be present, but is not the rate-limiting step while Boyd model suggested that film diffusion may be the controlling mechanism. Four isotherm models namely the Langmuir, Freundlich, Redlich–Peterson and Sips models were used for describing the adsorption process. The inclusion of non-linear isotherm models together with four error functions (ARE, EABS, χ 2 and MSPD) suggested the Langmuir model best described the adsorption process. The Langmuir isotherm predicted the maximum monolayer adsorption capacity of 90.8 mg g −1 . Thermodynamic studies showed that adsorption system is spontaneous and endothermic in nature. Regeneration of WS was investigated using three different solvent solutions and the results showed 0.1 M NaOH was able to regenerate and improve the adsorption capability of WS. Based on all the data in this study, WS is a potential low-cost material for the removal of MG.

Water remediation using low cost adsorbent walnut shell for removal of malachite green: Equilibrium, kinetics, thermodynamic and regeneration studies

This study evaluates different methods to determine points of zero charge (PZCs) on five organic materials, namely maple sawdust, wood ash, peat moss, compost, and brown algae, used for the passive treatment of contaminated neutral drainage effluents. The PZC provides important information about metal sorption mechanisms. Three methods were used: (1) the salt addition method, measuring the PZC; (2) the zeta potential method, measuring the isoelectric point (IEP); (3) the ion adsorption method, measuring the point of zero net charge (PZNC). Natural kaolinite and synthetic goethite were also tested with both the salt addition and the ion adsorption methods in order to validate experimental protocols. Results obtained from the salt addition method in 0.05 M NaNO3 were the following: 4.72 ± 0.06 (maple sawdust), 9.50 ± 0.07 (wood ash), 3.42 ± 0.03 (peat moss), 7.68 ± 0.01 (green compost), and 6.06 ± 0.11 (brown algae). Both the ion adsorption and the zeta potential methods failed to give points of zero charge for these substrates. The PZC of kaolinite (3.01 ± 0.03) was similar to the PZNC (2.9-3.4) and fell within the range of values reported in the literature (2.7-4.1). As for the goethite, the PZC (10.9 ± 0.05) was slightly higher than the PZNC (9.0-9.4). The salt addition method has been found appropriate and convenient to determine the PZC of natural organic substrates.

Determination of point of zero charge of natural organic materials.

Adsorption can be efficiently employed for the removal of various toxic dyes from water and wastewater. In this article, the authors reviewed variety of adsorbents used by various researchers for the removal of malachite green (MG) dye from an aqueous environment. The main motto of this review article was to assemble the scattered available information of adsorbents used for the removal of MG to enlighten their wide potential. In addition to this, various optimal experimental conditions (solution pH, equilibrium contact time, amount of adsorbent and temperature) as well as adsorption isotherms, kinetics and thermodynamics data of different adsorbents towards MG were also analyzed and tabulated. Finally, it was concluded that the agricultural solid wastes and biosorbents such as biopolymers and biomass adsorbents have demonstrated outstanding adsorption capabilities for removal of MG dye.

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Malachite green “a cationic dye” and its removal from aqueous solution by adsorption

Peat of Brunei Darussalam shows a great potential for the removal of methylene blue (MB) and malachite green (MG) dyes from aqueous solution. Carefully controlled batch experiments performed by changing one parameter at a time indicate that the optimum time periods of agitation and settling required for maximum removal of MB are 2.0 and 1.0 h, respectively, while these values for MG are 4.0 and 1.0 h, respectively. The optimum pH is determined to be the ambient value, and under the optimum conditions, 90 % removal of both dyes was determined under laboratory conditions. The equilibrium adsorption data analyzed for various isotherm models suggest that the Sips and Redlich–Peterson (R–P) models are valid for MB and MG, respectively. Further, thermodynamic studies show that the adsorption of both dyes on peat is spontaneous and endothermic. The adsorption capacities (q
 max) of MB and MG dyes on peat are 0.45 and 0.31 mmol g−1, respectively. Characterization of the surfaces of peat before and after treatment of dyes by SEM and FTIR provides conclusive evidence of adsorption of both dyes. Kinetics studies indicate that the adsorption of both MB and MG dyes is favored toward the pseudo-second-order model, with a little contribution of MG to the pseudo-first-order model. These results suggest that peat is a potential low-cost adsorbent for the removal of MB and MG dyes.

Sorption characteristics of peat of Brunei Darussalam IV: equilibrium, thermodynamics and kinetics of adsorption of methylene blue and malachite green dyes from aqueous solution

Artocarpus odoratissimus (Tarap) skin shows great potential as an effective low-cost biosorbent for toxic dyes, methylene blue (MB), and methyl violet 2B (MV). The Langmuir adsorption isotherm leads to the maximum biosorption capacities of this biomass, whose point of zero charge was at pH 4.4, of 0.577 mmol g−1 (184.6 mg g−1) and 0.349 mmol g−1 (137.3 mg g−1) for MB and MV, respectively. The Sips isotherm model is the best fit for adsorption of MB, while both the Langmuir and Sips models are in good agreement for MV. Mass transfer of dye species from solution to the biosorbent phase is fast with 50% dye being removed in less than 1 min following the pseudo-second-order kinetics.

Artocarpus odoratissimus skin as a potential low-cost biosorbent for the removal of methylene blue and methyl violet 2B

Peat collected from Panaga, Brunei Darussalam, shows strong affinity towards the adsorption of Congo red (CR) dye from aqueous solution. The adsorption capacity of Bruneian peat under optimized conditions of shaking time, settling time, and medium pH is determined to be 10.1 mg g−1 at equilibrium. Adsorption of CR on Bruneian peat follows monolayer adsorption with small contribution to multilayer formation qualifying the validity of the Redlich–Peterson model, which is further supported by error function determination. In addition, changes in peat structure and surface were studied using scanning electron microscopic and X-ray fluorescence techniques. Kinetics studies were in agreement with the pseudo-second-order model and the adsorption reaction proceeds according to intra-particle diffusion.

Sorption characteristics of peat of Brunei Darussalam V: removal of Congo red dye from aqueous solution by peat

Peat has been used for the removal of various dyes by adsorption. This study presents a new approach to increase the efficiency of peat for the removal of crystal violet (CV) dye from synthetic wastewater. The use of yeast-treated peat (Y peat) resulted in higher adsorption capacity than using untreated peat. Other factors that would affect the adsorption process, such as dye concentration, pH, and temperature, were also investigated. The dye uptake by peat and Y peat was supported by thermodynamics and kinetics studies. The Langmuir, Freundlich, Temkin, Dubinin–Radushkevich, and Sips models were applied to the adsorption studies. Experimental data based on linear regression, simulated isotherms, and error analyses showed that the adsorption of CV followed the Sips model with maximum adsorption capacities of 8.16 and 17.95 mg g−1 for peat and Y peat, respectively. Thermodynamics studies revealed that the adsorption process was both spontaneous and endothermic in nature. Kinetics data fitted to the pseudo-first-order, pseudo-second-order, Elovich, intra-particle diffusion, and Boyd models revealed that adsorption of CV on peat and Y peat followed the pseudo-second-order model, which was supported by the diffusion mechanism.

Removal of crystal violet dye from aqueous solution using yeast-treated peat as adsorbent: thermodynamics, kinetics, and equilibrium studies

In this study, the feasibility of utilizing Artocarpus odoratissimus skin (“Tarap” skin or TS) as a potential adsorbent for the removal of crystal violet dye was investigated. X-ray fluorescence, Fourier Transform Spectroscopic, and scanning electron microscopic investigation of TS and its NaOH-treated form (NaOH-TS) before and after interaction with crystal violet (CV) cationic dye indicate that the dye shows a strong affinity toward the adsorbent, which is enhanced upon the treatment with a NaOH solution. Decrease in the concentration of metal ions on the TS/NaOH-TS is indicative of the contribution of an ion-exchange mechanism owing to the positive charge of CV molecules. Comparison of experimental adsorption curves with calculated curves point the way toward the agreement with the Langmuir isotherm among the six models tested (Langmuir, Freundlich, Temkin, Dubinin–Radushkevich, Redlich–Peterson, and Sips) under optimized conditions with maximum adsorption capacity of 118 mg g−1 for TS which is...

Adsorption of crystal violet dye from aqueous solution onto chemically treated Artocarpus odoratissimus skin: equilibrium, thermodynamics, and kinetics studies

Tasneem Zehra

Papers

Sorption characteristics of peat of Brunei Darussalam IV: equilibrium, thermodynamics and kinetics of adsorption of methylene blue and malachite green dyes from aqueous solution

Artocarpus odoratissimus skin as a potential low-cost biosorbent for the removal of methylene blue and methyl violet 2B

Sorption characteristics of peat of Brunei Darussalam V: removal of Congo red dye from aqueous solution by peat

Removal of crystal violet dye from aqueous solution using yeast-treated peat as adsorbent: thermodynamics, kinetics, and equilibrium studies

Adsorption of crystal violet dye from aqueous solution onto chemically treated Artocarpus odoratissimus skin: equilibrium, thermodynamics, and kinetics studies