Present paper involved the review of fixed-bed column studies for removal of various contaminants from synthetic wastewater. Basic concept of adsorption, its types (i.e., chemisorption and physisorption) and its mechanism, adsorbents and adsorbates were included. Comparison of batch and column adsorption study is mentioned. Complete study of breakthrough curve for designing adsorptive column is interpreted. This paper explicates the detailed explanation of various process parameters and isotherm models for column study. Fixed-bed adsorption studies using various adsorbates, i.e., metal, ion, dye and other hazardous materials, are reviewed, in which adsorption of chromium metal is most exploitable. Conclusion and some challenges for utilization in real world are also exposed.

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Fixed-bed column adsorption study: a comprehensive review

Adsorption of congo red and methylene blue dyes on an ashitaba waste and a walnut shell-based activated carbon from aqueous solutions: Experiments, characterization and physical interpretations

Olive stones have been widely used as a renewable energy biowaste source. As they are rich in elemental carbon (40–45 wt%), much research focussed on effectively converting olive stones, as precursors, into activated carbon adsorbents. However, only a few studies have concentrated on summarising the various techniques used to produce activated carbon from olive stone. This article reviews the research undertaken on the production and application of activated carbon as an adsorbent from olive stones for wastewater treatment. Various physical, chemical and physico-chemical treatments to remove heavy metals, organics and dyes are discussed, and the resultant adsorption capacities are reported. In several cases, very high adsorption capacities are recorded. Finally, the future prospects of these materials as adsorbents are discussed, and after further development work, olive stone-derived activated carbons have great potential especially in the area of organic polluted wastewaters.

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Production and applications of activated carbons as adsorbents from olive stones

Effects of operating parameters and coexisting ions on the efficiency of heavy metal ions removal by nano-fibrous metal-organic framework membrane filtration process.

Breakthrough curve analysis by simplistic models of fixed bed adsorption: In defense of the century-old Bohart-Adams model

Cr(VI) adsorption by a green adsorbent walnut shell: Adsorption studies, regeneration studies, scale-up design and economic feasibility

Cr(VI) is a toxic water pollutant, which causes cancer and mutation in living organisms. Adsorption has become the most preferred method for removal of Cr(VI) due to its high efficiency and low cost. Peanut and almond shells were used as adsorbents in downflow fixed bed continuous column operation for Cr(VI) removal. The experiments were carried out to scrutinise the adsorptive capacity of the peanut shells and almond shells, as well as to find out the effect of various operating parameters such as column bed depth (5–10 cm), influent flow rate (10–22 ml min−1) and influent Cr(VI) concentration (10–20 mg L−1) on the Cr(VI) removal. The fixed bed column operation for Cr(VI) adsorption the equilibrium was illustrated by Langmuir isotherm. Different well-known mathematical models were applied to the experimental data to identify the best-fitted model to explain the bed dynamics. Prediction of the bed dynamics by Yan et al. model was found to be satisfactory. Applicability of artificial neural network (ANN) modelling is also reported. An ANN modelling of multilayer perceptron with gradient descent and Levenberg-Marquardt algorithms have also been tried to predict the percentage removal of Cr(VI). This study indicates that these adsorbents have an excellent potential and are useful for water treatment particularly small- and medium-sized industries of third world countries. Almond shell represents better adsorptive capacity as breakthrough time and exhaustion time are longer in comparison to peanut shell.

Comparative study of adsorptive removal of Cr(VI) ion from aqueous solution in fixed bed column by peanut shell and almond shell using empirical models and ANN

Long-term exposure of Cr(VI) causes severe health effects to the living beings. A continuous fixed bed experimental study is carried out by using pistachio shell as green and eco-friendly adsorbent for Cr(VI) adsorption. Effects of several operating parameters on Cr(VI) removal were investigated using the breakthrough curves (
 $$ \frac{C_t}{C_0} $$
 versus time) and determination of saturation time (
 $$ \frac{C_t}{C_0}\le 1\Big).\kern0.5em $$
 Cr(VI) adsorption equilibrium was illustrated by Langmuir isotherm. Different kinetic models like Yan et al. (2001), Thomas (1944), Yoon-Nelson (1984), and Bohart-Adams model(1920) were applied to study the dynamics of the adsorption process.Yan et al. model was found more effective compare to other kinetic models.This studyshowed that the pistachio shells, green adsorbent, have potential adsorption capacity for Cr(VI) ions. Applicability of GA-ANN hybrid model has been tested to predict the percentage removal of Cr(VI).

Removal of Cr(VI) from Its Aqueous Solution Using Green Adsorbent Pistachio Shell: a Fixed Bed Column Study and GA-ANN Modeling

Cu(II) adsorption in continuous column using green adsorbents like peanut and almond shell was investigated. Fourier transform infrared (FTIR) spectroscopy, Brunaer-Emmett-Teller (BET) analysis, scanning electron microscopy (SEM), and Point of Zero charge (pHpzc) determination have been used for characterization of the adsorbents. Experiments were conducted at various operating conditions to calculate the adsorption capacity of the adsorbents. Adsorption studies signify that both the adsorbents have good adsorptive capacity for Cu(II) ion. Equilibrium of adsorption was described using Langmuir isotherm and the highest qmax value for both the adsorbent were obtained at an operating condition of 20 ml/min flow rate, 15 mg/L influent Cu(II) concentration, and 7 cm bed depth. Regeneration of both the adsorbents suggests that these adsorbents can be used several times for Cu(II) removal. Seven different kinetic models were tested among which the modified dose response model was fitted well for peanut shell and the Thomas model was fitted well for almond shell. These fitted models were further used for scale-up design. Regeneration studies show that peanut shell and almond shell are useful up to the fifth adsorption cycle. Application of these adsorbents with industrial effluent was also reported. This study reveals that peanut and almond shells can be used for Cu(II) removal for industrial wastewater.

Cu(II) removal using green adsorbents: kinetic modeling and plant scale-up design

Chromium (VI) is a well-known toxic, industrial, water pollutant which has various, adverse effects on environmental health. Utilization of agricultural waste in effluent water treatment would minimize the problem of water pollution. The present study deals with the use of three types of nut shells for Cr(VI) removal. Adsorbents are characterized, using point of zero charges (pHpzc), FTIR, BET surface area analysis, and SEM. The variation of different operating parameters on metal removal was conducted. The best sorption kinetic model was pseudo-second order. The adsorption process is both physical and chemical, and this depends on temperature. The Cr(VI) adsorption is spontaneous and endothermic. According to isotherm studies, Langmuir isotherm model fits fairly well for all adsorbents. Regeneration studies suggest that the adsorbents have proper regeneration criteria and can be used for multiple times. Study on RBC count of Gallus gallus domesticus gives concrete evidence of deadly effects of Cr(VI). It also figures out that the effluent solution treated with bio-adsorbents is less harmful. The scale-up design procedure is reported here. This study proved that groundnut shell, walnut shell, and almond shell have immense potential and can be utilized even after regeneration as replacement of commercial adsorbents for industrial wastewater. GA–ANN modeling has been developed for the best possible wastewater treatment management.

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Munmun Banerjee

Papers

Cr(VI) adsorption by a green adsorbent walnut shell: Adsorption studies, regeneration studies, scale-up design and economic feasibility

Comparative study of adsorptive removal of Cr(VI) ion from aqueous solution in fixed bed column by peanut shell and almond shell using empirical models and ANN

Removal of Cr(VI) from Its Aqueous Solution Using Green Adsorbent Pistachio Shell: a Fixed Bed Column Study and GA-ANN Modeling

Cu(II) removal using green adsorbents: kinetic modeling and plant scale-up design

Adsorptive removal of Cr(VI) from aqueous solution: kinetic, isotherm, thermodynamics, toxicity, scale-up design, and GA modeling