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Environmental fate & pathways

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additional information on environmental fate and behaviour
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: No GLP, no guidelines followed Read across from a similar substance which has the same main component and with a different counter ion that doesn't influence the characteristics related to the specific end-point

Data source

Reference
Reference Type:
publication
Title:
Adsorption characteristics of malachite green on activated carbon derived from rice husks produced by chemical–thermal process
Author:
I.A. Rahman, B. Saad, S. Shaidan, E.S. Sya Rizal
Year:
2005
Bibliographic source:
Bioresource Technology 96 (2005) 1578–1583

Materials and methods

Principles of method if other than guideline:
Phosphoric acid (H3PO4) and sodium hydroxide (NaOH) treated rice husks, followed by carbonization in a flowing nitrogen were used to study the adsorption of Malachite Green (MG) in aqueous solution. The effect of adsorption on contact time, concentration of MG and adsorbent dosage of the samples treated or carbonized at different temperatures were investigated.
Type of study / information:
Adsorption

Test material

Reference
Name:
Unnamed
Type:
Constituent

Results and discussion

Any other information on results incl. tables

Adsorption behaviour of PCP adsorbent

fMG(fraction of MG) is 100% for CA up to 100 mg/L. It decreases with increasing carbonization temperature for both PCP10 and PCP20. Again, the PCP10 and PCP20 that was carbonized at 500°C showed an improvement in the overall uptake capacity up to 40 mg/L and 60 mg/L respectively. The doses increase as carbonized temperature decreases and H3PO4 concentration increases. Only three samples were able to remove 100% of 100 mg/L MG in 100 mL solution, PCP10 (500°C) = 0.8 g, PCP20 (500°C) = 0.6 g, and PCP20 (400°C) = 1.0 g, and CA required 0.5 g. The increase in adsorption capacity for the PCP10 and PCP20 carbonized at 500°C is most likely related to the maximum surface area created and the availability of more adsorption sites for the bulky organic group.

Results indicate that MG adsorption is more pronounced on the carbon surface rather than on silica surface.

Adsorption behaviour of NCP adsorbent

It can be readily seen that fMG increases with increasing treatment temperature, although at a slower rate when compared to CA. The raw husks failed to adsorb MG to a satisfactory level due to the absence of large pores to accommodate the bulky organic group of MG. Similar trends were observed on the fMG verses concentrations and adsorbent doses. Results indicate that 0.1 g NCP100C was able to adsorb up to 40 mg/L MG in 100 mL and 0.6 g/100 mL required to remove 100 mg/L. This indicates that by removing silica, adsorption sites on carbon increase and this enhanced the adsorption capacity.

Applicant's summary and conclusion

Conclusions:
It is expected that the Malachite Green is preferably adsorbed on carbon surface as the presence of silica to a certain extent, can retard the adsorption capacity. Thus, rice husks based material can provide attractive alternative adsorbents to remove Malachite Green in wastewater from textile industries and aquaculture activities.
Executive summary:

Phosphoric acid (H3PO4) and sodium hydroxide (NaOH) treated rice husks, followed by carbonization in a flowing nitrogen were used to study the adsorption of Malachite Green (MG) in aqueous solution. The effect of adsorption on contact time, concentration of MG and adsorbent dosage of the samples treated or carbonized at different temperatures were investigated. The results reveal that the optimum carbonization temperature is 500 C in order to obtain adsorption capacity that is comparable to the commercial activated carbon for the husks treated by H3PO4. It is interesting to note that MG adsorbed preferably on carbon-rich than on silica rich-sites. It is found that the behaviour of H3PO4 treated absorbent followed both the Langmuir and Freundlich models while NaOH treated best fitted to only the Langmuir model.