Hi Ain,
I can imagine such a scenario eating porridge every day for my breakfast ;-). Also, material such as okra contain gum that can leach out giving rise to your observation. Palm kernel cake, an abundantly available by-product from the palm oil mill, is relatively rich in protein (Article Effect of palm kernel cake as protein source in a concentrat...
) that could leach out and cause that slimy appearance.I would first check whether the agri-waste you have choosen has other more valuable applications than being an adsorbent. If the answer is yes, search for another by-product. Ligno-cellulosic material with low extractables should not give you the same problems. However, washing of the raw material is still carried out to remove ash and other matter that can interfere (the less is leaching out the better from an industrial point of view because of cost of wastewater treatment).
If the answer is no (there is no other more valuable app), I would try to extract the slimy substance first to avoid problems downstream and characterise it. The extracted substance(s) may be useful for other applications, e.g. as natural coagulant (Article Use of Cassia javahikai seed gum and gum-g-polyacrylamide as...
), food thickener, industrial stabiliser (Article Characterization of gum isolated from Camelina seed
), etc.Use the extraction cake to repeat your adsorption experiment. Review the adsorbent concentration used. I prefer to use 0.5 g to 1 g in 100 mL (Article Dye removal using carbonized biomass, isotherm and kinetic studies
;Article Olive oil waste as a biosorbent for heavy metals
).For effect of adsorbent concentration on adsorption capacity and process you can refer to http://linkinghub.elsevier.com/retrieve/pii/S1383586606003066 and other papers in the literature. If not done so already ensure you have negative (solution only, adsorbent only) and positive controls (commercial adsorbent or sorbent from other research team of known sorption capacity) to account for non-sorption related phenomena.
If the adsorption performance is not satisfactory you need to consider to tune the adsorbent by changing its surface chemistry (refer to Mohammed Danish his work) or carbonisation. Carbonised agri-residues for dye removal have proven successful largely due to the enhanced surface area and stability during regeneration.
Hope this helps a bit? If you want you can drop by at our UniKL MICET campus in Melaka to discuss further with sorption experts such as Dr Danish, Dr Norzahir or colleagues from the food and polymer section (regarding thickener).
All the best Rob.
Thank you so much for all the ideas and suggestions Robert Thomas Bachmann ! will look for the discussion with your colleagues one day! =)
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