Literary Review

Three articles were reviewed in which waste water treatment was conducted through a

biosorption method on dyes. In order to improve the efficiency of biosorbents, studies have been

conducted on increasing its biosorption capacity. Sadaf et al. investigated how immobilization affects

biosorption.

Peanut husk in three different forms were used: native, CH3COOH treated and Na-alginate. Both

batch and continuous process was performed in order to remove Indosol Yellow BG dye. The batch

process was set up in an orbital shaking incubator and the dye concentration was determined with UV-

vis spectroscopy after the experiment. Meanwhile, a fixed-bed column packed with a given quantity of

peanut husk was employed for a continuous process study. In addition to the variable in the form of the

husk, the initial concentration of the dye solution was also varied.

In a FT-IR analysis of the before and after loading of the dye solution, it was discovered that two new

peaks were introduced in the acetic acid treated and immobilized peanut husk. This is explained to be

the exposure of a buried amino acid group on the surface of the husk, which leads to an increase in

biosorption capacities. In summary, Sadaaf et al. found that biosorption uptake decreased with pH,

increased as contact time was increased, decreased with biosorbent dose, increased with initial dye

concentration and decreased with temperature.

TABLE OF SUMMARY FOR KINETIC AND EQUILIBRIUM

Based on the given data, the kinetics of biosorption follows pseudo second order and equilibrium data

best fits a Langmuir isotherm model. It is believed that intraparticle diffusion should be occurring,

however it is possible that surface adsorption could conflict with their chosen model. Through their fixed

bed column, they determined that maximum bed height and initial dye concentrations led to the

quickest dye removal.

In review of this article, there are few flaws to their logic and reasoning. It was really detailed in the

amount of variables that was studied. It must have taken countless experiments to gather data changing

pH, dye concentrations or temperature. It is also one of the few articles that explicitly stated that each

experiment had three reruns. The one thing that stood out is that they decided to only use native

peanut husk for their continuous experiment. It is questionable why one of the more efficient

biosorbent weren't chosen.

Another research group took a different approach to waste water treatment. Mohammad et al.

investigated biosorbents for removing safranin-O, in order to find a cheap and effective alternative to

commercially activated carbons. Pineapple peels had already been acknowledge for efficient biosorption

for removing dyes, thus the idea was tested for applications towards safranin-O. Mohammad et al. used

grounded up pineapple peels from a local market and conducted a batch process experiment. Similar to

Sadaf et al., the same variables were examined, including pH, initial concentration, contact time, initial

concentration of safranin-O and dose of adsorbate. To draw comparisons, increasing the initial

concentration and adsorbate dose led to higher biosorption efficiency. However, increased contact time

actually decreased overall biosorption efficiency and higher pH led to better biosorption.

Mohammad et al. did not present a kinetic model analysis, but instead focused on the

equilibrium isotherms. The conclusion was that their data matched Freundlich isotherm. It gave them

the highest R2 value of 0.985. However, the strange thing is that Langmuir isotherm also gives a high R2

value of 0.9593. A plot of the experimental versus theoretical data was given and it seems that Langmuir

matches much better than Freundlich. It doesn't look like they addressed what happened.