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10.3.6 Agricultural Waste
Agricultural waste defines the waste generated by human beings after processing of
agricultural activity. Agricultural waste is a promising biosorbent for remediation of
hazardous metals from contaminated water because of its enormous availability,
cost-efficiency, superior adsorption ability and selectivity, and ease of processing,
separation, and regeneration of adsorbent. Nowadays researchers are highly concerned about the utilization of agricultural waste which can act as a good alternative
of commercially available activated carbon adsorbent and therefore achieving the
global concern to reduce environmental pollution by “treating waste by waste”.
Agricultural wastes are mainly lignocellulosic biomass consisting of lignin, pectin, cellulose, and hemicellulose. The functional groups like carbonyl, hydroxyl,
and ether are responsible for binding heavy metals via chelating, coordinating, and
hydrogen bonding. In spite of having noticeable characteristics of good adsorbent,
use of untreated agricultural wastes indulges with severe problem. These wastes
cannot be disposed of randomly as it elevates chemical and biological oxygen
demand as well as total organic carbon to the water systems.
Rice husk is readily available, cheap adsorbent consisting of cellulose followed
by lignin, hemicellulose, and mineral ash. The utilization of rice husk is a major
concern for developing countries like India, China, and Indonesia where rice is the
main food crop for livelihood. The presence of functional groups like hydroxyl,
silanol, and siloxane in rice husk reflects strong affinity toward heavy metal cations.
Rice husk was found to be effective low-cost adsorbent in the removing metal like
Ni, Cr, Zn, Pb, and Cu. A study on adsorption efficiencies of nine different toxic
heavy metals by rice husk found adsorption capacity with the values ascending in
subsequent order nickel < zinc ≈ cadmium ≈ manganese ≈ cobalt < copper ≈ mercury < lead. Natural rice husk and rice husk modified by activated carbon using O 3
were used for the removal of chromium showing that by modification higher
removal efficiency was achieved. Though rice husk is efficient adsorbent, it still
needs modification to enhance its adsorption capacity. It was reported that modified
rice husk removes 125.94 mg g
−1
of cadmium when stirred with NaOH for 24 h,
whereas non-modified one gives only 73.96 mg g
−1
adsorption at an optimum pH of
6.5. Biochar which is a byproduct from pyrolysis of rice husk can be used for chromium removal with the adsorption capacity of 95%. Another experimental study on
the copper removal observed an adsorption capacity of 17.9 mg g
−1
using rice husk.
Rice husk can act as a promising adsorbent for the adsorption of lead because of the
following mechanisms: surface complexation with –COOH and –OH groups, ion
exchange with calcium and magnesium, and forces of attraction.
Coconut shell is well-known common low-cost adsorbent under agricultural
waste which is very abundant in tropical countries. Heavy metals such as Cu, Pb,
Ni, Zn, and Cr are efficiently removed from wastewater by coconut shell. 7.5 million tons of coconut per year is produced in India, and the waste has been used as
adsorbent for treatment of effluent. Coconut coir pith comprises cellulose 35%, fats
1.8%, lignin and resin 25.2%, pentosans 7.5%, ash 8.7%, moisture 11.9%, and the
M. Maharana et al.
10.3.6 Agricultural Waste
Agricultural waste defines the waste generated by human beings after processing of
agricultural activity. Agricultural waste is a promising biosorbent for remediation of
hazardous metals from contaminated water because of its enormous availability,
cost-efficiency, superior adsorption ability and selectivity, and ease of processing,
separation, and regeneration of adsorbent. Nowadays researchers are highly concerned about the utilization of agricultural waste which can act as a good alternative
of commercially available activated carbon adsorbent and therefore achieving the
global concern to reduce environmental pollution by “treating waste by waste”.
Agricultural wastes are mainly lignocellulosic biomass consisting of lignin, pectin, cellulose, and hemicellulose. The functional groups like carbonyl, hydroxyl,
and ether are responsible for binding heavy metals via chelating, coordinating, and
hydrogen bonding. In spite of having noticeable characteristics of good adsorbent,
use of untreated agricultural wastes indulges with severe problem. These wastes
cannot be disposed of randomly as it elevates chemical and biological oxygen
demand as well as total organic carbon to the water systems.
Rice husk is readily available, cheap adsorbent consisting of cellulose followed
by lignin, hemicellulose, and mineral ash. The utilization of rice husk is a major
concern for developing countries like India, China, and Indonesia where rice is the
main food crop for livelihood. The presence of functional groups like hydroxyl,
silanol, and siloxane in rice husk reflects strong affinity toward heavy metal cations.
Rice husk was found to be effective low-cost adsorbent in the removing metal like
Ni, Cr, Zn, Pb, and Cu. A study on adsorption efficiencies of nine different toxic
heavy metals by rice husk found adsorption capacity with the values ascending in
subsequent order nickel < zinc ≈ cadmium ≈ manganese ≈ cobalt < copper ≈ mercury < lead. Natural rice husk and rice husk modified by activated carbon using O 3
were used for the removal of chromium showing that by modification higher
removal efficiency was achieved. Though rice husk is efficient adsorbent, it still
needs modification to enhance its adsorption capacity. It was reported that modified
rice husk removes 125.94 mg g
−1
of cadmium when stirred with NaOH for 24 h,
whereas non-modified one gives only 73.96 mg g
−1
adsorption at an optimum pH of
6.5. Biochar which is a byproduct from pyrolysis of rice husk can be used for chromium removal with the adsorption capacity of 95%. Another experimental study on
the copper removal observed an adsorption capacity of 17.9 mg g
−1
using rice husk.
Rice husk can act as a promising adsorbent for the adsorption of lead because of the
following mechanisms: surface complexation with –COOH and –OH groups, ion
exchange with calcium and magnesium, and forces of attraction.
Coconut shell is well-known common low-cost adsorbent under agricultural
waste which is very abundant in tropical countries. Heavy metals such as Cu, Pb,
Ni, Zn, and Cr are efficiently removed from wastewater by coconut shell. 7.5 million tons of coconut per year is produced in India, and the waste has been used as
adsorbent for treatment of effluent. Coconut coir pith comprises cellulose 35%, fats
1.8%, lignin and resin 25.2%, pentosans 7.5%, ash 8.7%, moisture 11.9%, and the
M. Maharana et al.