I am really astounded that some people makes many clicks think they make contribution through saying good discussion, nice discussion and you are right ....etc and if write some things will be through copy and paste from others. In the final it is considered as contribution ?!!!!!!!

Rightly pointed out. This type of practice and experiementation will be limited to laboratory only. I can't see use of agriculture waste in large scale waste water treatment.

Heavy metal remediation of aqueous streams is of special concern due to recalcitrant and persistency of heavy metals in environment. Conventional treatment technologies for the removal of these toxic heavy metals are not economical and further generate huge quantity of toxic chemical sludge. Biosorption is emerging as a potential alternative to the existing conventional technologies for the removal and/or recovery of metal ions from aqueous solutions. The major advantages of biosorption over conventional treatment methods include: low cost, high efficiency, minimization of chemical or biological sludge, regeneration of biosorbents and possibility of metal recovery. Cellulosic agricultural waste materials are an abundant source for significant metal biosorption. The functional groups present in agricultural waste biomass viz. acetamido, alcoholic, carbonyl, phenolic, amido, amino, sulphydryl groups etc. have affinity for heavy metal ions to form metal complexes or chelates. The mechanism of biosorption process includes chemisorption, complexation, adsorption on surface, diffusion through pores and ion exchange etc. The purpose of this review article is to provide the scattered available information on various aspects of utilization of the agricultural waste materials for heavy metal removal. Agricultural waste material being highly efficient, low cost and renewable source of biomass can be exploited for heavy metal remediation. Further these biosorbents can be modified for better efficiency and multiple reuses to enhance their applicability at industrial scale.

The potential use of agricultural wastes as absorbents to isolate heavy metals in their adsorption capacity indicates that their absorption capacity is equal to or greater than the capacity of conventional absorbents. Using the modern molecular bio-technologies could lead to understanding the role of functional groups in bio-concentration. However, chemical processing may have higher absorption potential, possibly due to pH settings, for example. However, there are many rifts and need multiple reuse to enhance their industrial suitability. For example, cost-effective adjustment modes and re-evaluate AWBs as waste water containing several metals. When these obstacles are overcome, the process of removing routine sorbents by AWBs can be predictable in removing heavy metals from the next wastewater.

No scope.......... the cost of pre-treatment of the biomass is very high.

It has widely scope in agricultural frields.

Treatment of heavy metal pollutants as well as devlopment of bacteria that will take care of crude oil spills are two fields that may be relevant.

It`s important to do the treatment of heavy metal pollutants regarding the different isolating methods , but on the other hand the cost of these methods is very high , for that we have to work on cost effective methods.

It may be possible but more researches are required for easy and economical methods. Agricultural waste material being highly efficient, low cost and renewable source of biomass can be exploited for heavy metal remediation. Further these biosorbents can be modified for better efficiency and multiple reuses to enhance their applicability at industrial scale.

I think that most of agricultural waste have already other important use. So, these waste never will be used as adsorbent materials in the wastewater treatment.

Hello Hossam,

I agree on the part of lack of application on industrial-scale. I think that there should be continuity of research (i.e. on the part of R&D Departments of industry) and consistency in application on this area. Activated carbon, for example, here in the Philippines are most of the time yielded from waste products, such as coconut husks.

The major problem of agricultural waste is non availability in large quantity and being seasonal making it difficult to be utilized in large scale.

I am really astounded that some people makes many clicks think they make contribution through saying good discussion, nice discussion and you are right ....etc and if write some things will be through copy and paste from others. In the final it is considered as contribution ?!!!!!!!

I have same idea about it.

Lost time and reseach.

I think the use of these material

need a final destination corret to absorbent and a lot of adsorbent too.

This is not feaseble in industrial escale.

There are many adsorbents produced in the lab from agricultural waste and have been used for commercial production.

All such adsorbents have received patents.

Once a waste is composted and stabilized it is no longer a waste but a value added new product.

You are right that is has great environmental utility in compost as absorbent material.

The filling of porous pillows with compost is a barrier to surface water contamination on building sites.

The use of compost filters can be used for both water decomtamination and for issues of air filtration to aid in the trapping of ammonia in poultry houses.

In eutropified lagoons the use of straw is often used as adsorbent. Many established and to be established opportunities in this area.

"What is the future of using agricultural wastes as adsorbent on an industrial scale?" is a good topic for discussion.

A current approach to “waste” management is to perceive waste as a possible resource of mean to resource recovery. A successful industrial example is activated carbon produced from agricultural wastes including bamboo, coconuts, peach pits, and wood. Another example in transition is municipal and agricultural waste waters being harvested for the nutrients nitrogen and phosphorous; the research spans the past few decades with successful application at the local level and very few industrial scale applications. Besides the challenges of research and technology to convert wastes to useful products, there are also economics constraints including creating markets for the products and efficient, affordable transportation to those markets. The complexity of the system is a contributor to the lack of quick and successful application of research to an industrial scale.

Dear colleagues,

Thanks a lot for responding to my question. However, I still did not get a comfortable answer. I tried many agricultural wastes (without treatment except for washing) for removal of many pollutants, and I found some of them having better adsorption capacity than activated carbon. So, I know the advantages of these economic and effective adsorbents. The questions are:

1) why these adsorbents were not used on commercial scale as ADSORBENTS?

2) Is there ant probability that such materials will be used as ADSORBENTS in the future? or working with such materials is a waste of time as one colleague mentioned in his answer?

I have always been thinking of this as well, that the direction of the research should be toward implementation outside the lab. However, no knowledge is wasted.

I think may be the disposal of these adsorbents after their life cycle poses a serious environmental issues.

The absorbing of the toxic principal with its disposable does not necessarily mean the environment will be damaged. If the the offending substances are properly diluted and put under a condition that does not promote their liberation at excess concentration it is able to serve a good purpose. I think that the custody and train of the handling and monitoring are very important in all our systems.

But what we will do with the removed toxic metals finally?.. even if we dilute, still the disposal will be problem..I think due the secondary pollution of adsorption process, the adsorbents are not commercially viable in large scale..

These substrates have proved promising adsorbents for the removal of pollutants from wastewater and its future is very bright.

Hi Hossam Altaher ,

I agree with Andrea M Dietrich , Nleonu Emmanuel Chile and Laura Bulgariu . Industrially successful carbon-based adsorbents must fulfill many criteria, which not all agricultural residues can attain:

1. Low ash content and low amount of pollutants/heavy metals present in ash (minimal washing required, cost-saving)

2. High lignin content (high char yield)

3. High surface area

4. Available throughout the year (some biomass is seasonal)

5. Easy to store without undergoing degradation (minimal losses, cost-saving)

6. Low moisture content (minimal need for drying)

7. Residue must be available at large quantities in factories (minimal cost for transport)

8. Residue must be accessible by third parties (the adsorbent producer) via long-term contracts

9. Its use for alternative applications must be limited and not economically competitive

10. Must be of high density for cost-effective transport

11. Must be easy to feed into carbonizer (fibrous material may require additional processes such as pelletisation which increases cost)

12. Carbonised particles must be mechanically stable during operation of adsorber unit to prevent washout (rice husk/straw char very brittle)

13. Carbonised particles should be of 1-2 mm size for practical reasons (smaller particles have a greater surface area but increase the pressure drop, smaller particles are also more difficult to retain in adsorber unit).

14. Spent adsorbent must be able to withstand many regeneration cycles without loosing its adsorption capacity.

As you rightly say, there are thousands of publications on the use of carbonised / activated agricultural residues but only few if any take into consideration all the criteria that an industrially successful adsorbent must fulfill. In the introduction most claim the material is low cost without providing evidence, and often ignore amount produced, how to collect it, moisture content/issue of drying, alternative applications and so on.

Coconut shell and to a lesser extend palm kernel shell are well established adsorbents here in Malaysia and China. When you go to https://offer.alibaba.com and key in 'Activated carbon' you will see that a lot is produced from coconut shell for water treatment.

There is a future for agricultural residues as adsorbent, but research must be conducted holistically taking into account the above criteria (and any other I could not think of right now). Life cycle assessment along with life cycle cost analysis can go a long way to pin-point the bottlenecks potential candidates face and guide the researcher towards the right research questions. Things like long-term supply contracts are not part of these tools so be aware of the limitations.

Hope this answers your question?