221
• Removal of Cadmium (Cd)
Cadmium and its compounds as compared to other heavy metals are relatively
more water soluble and therefore are mobile and tend to bioaccumulate in environmental compartments. Various agricultural wastes are used to adsorbed Cr and its
compounds from aqueous solution. In some studies, rice and wheat bran were analyzed for cadmium adsorption, and excellent results were reported (Motaghi and
Ziarati 2016). Studies were conducted on use of other agricultural waste including
rice husk and rice polish in both pristine and composite forms for effective cadmium
removal. The bark of some plants including Picea glehnii and Abies sachalinensis
and biomass of dried plants (Parthenium) were checked for cadmium removal.
Adsorption experiments performed using hazelnut shells, green shell, walnut shells,
and peanut hulls exhibited good results toward cadmium adsorption. Some other
adsorption studies conducted using activated carbon prepared coir pith, bagasse
pith, and dates and peanut shells. Their cadmium adsorption capacity was found to
be up to 98% (Sud et al. 2008).
Ansari and coworker conducted as a study to produce a valuable absorbent of
walnut agricultural waste. Walnut shell has characteristics including large carbon
contents, low humidity, and availability and is successfully used as a cadmium
adsorbent. Preparing activated carbon with less heat energy usage can be considered
as an alternative adsorbent for industrial activated carbon. The activated carbon
derived from walnut shell was significantly effective in removing cadmium from the
aquatic environment. They obtained maximum cadmium adsorption at pH 6. The
Cd adsorption by activated carbon produced from walnut shell was described in two
adsorption isotherms, Langmuir and Freundlich. These results showed that walnut
shell as an agricultural waste can be used for the synthesis of effective cadmium
absorbent (Ansari et al. 2018).
• Removal of nickel (Ni)
Adsorption experiments for Ni removal were conducted using Cassia fistula biomass, and the obtained results showed 99–100% adsorption capacity (Alam et al.
2018). Nickel removal and sequestering efficiency of waste tea leaves were also
analyzed. Excellent results were obtained in this regard (Shah et al. 2015). Other
agricultural wastes including hazelnut, sawdust of maple, peanut, cotton seeds, walnut, black locust and oaks, pecan, soybeans, and corncobs have been reported as
promising materials; round nutshells in natural or altered form were also used for
nickel removal from aqueous media (Sud et al. 2008). Sugarcane bagasse in unmodified form showed more than 80% adsorption capacity (Garg et al. 2008). In one
study, agricultural waste, such as rise husk, and industrial waste, such as fly ash,
were analyzed for adsorption of heavy metals in electroplating industries. The
obtained result showed that rice husk was effective in the simultaneous removal of
iron, leads, and nickel, while fly ash removed cadmium and copper. This study concluded that the percentage of heavy metal removal is affected by many factors
including dose adsorbent, contact time, and optimum pH range (Fan et al. 2017).
8 Agricultural Waste Absorbents for Heavy Metal Removal
• Removal of Cadmium (Cd)
Cadmium and its compounds as compared to other heavy metals are relatively
more water soluble and therefore are mobile and tend to bioaccumulate in environmental compartments. Various agricultural wastes are used to adsorbed Cr and its
compounds from aqueous solution. In some studies, rice and wheat bran were analyzed for cadmium adsorption, and excellent results were reported (Motaghi and
Ziarati 2016). Studies were conducted on use of other agricultural waste including
rice husk and rice polish in both pristine and composite forms for effective cadmium
removal. The bark of some plants including Picea glehnii and Abies sachalinensis
and biomass of dried plants (Parthenium) were checked for cadmium removal.
Adsorption experiments performed using hazelnut shells, green shell, walnut shells,
and peanut hulls exhibited good results toward cadmium adsorption. Some other
adsorption studies conducted using activated carbon prepared coir pith, bagasse
pith, and dates and peanut shells. Their cadmium adsorption capacity was found to
be up to 98% (Sud et al. 2008).
Ansari and coworker conducted as a study to produce a valuable absorbent of
walnut agricultural waste. Walnut shell has characteristics including large carbon
contents, low humidity, and availability and is successfully used as a cadmium
adsorbent. Preparing activated carbon with less heat energy usage can be considered
as an alternative adsorbent for industrial activated carbon. The activated carbon
derived from walnut shell was significantly effective in removing cadmium from the
aquatic environment. They obtained maximum cadmium adsorption at pH 6. The
Cd adsorption by activated carbon produced from walnut shell was described in two
adsorption isotherms, Langmuir and Freundlich. These results showed that walnut
shell as an agricultural waste can be used for the synthesis of effective cadmium
absorbent (Ansari et al. 2018).
• Removal of nickel (Ni)
Adsorption experiments for Ni removal were conducted using Cassia fistula biomass, and the obtained results showed 99–100% adsorption capacity (Alam et al.
2018). Nickel removal and sequestering efficiency of waste tea leaves were also
analyzed. Excellent results were obtained in this regard (Shah et al. 2015). Other
agricultural wastes including hazelnut, sawdust of maple, peanut, cotton seeds, walnut, black locust and oaks, pecan, soybeans, and corncobs have been reported as
promising materials; round nutshells in natural or altered form were also used for
nickel removal from aqueous media (Sud et al. 2008). Sugarcane bagasse in unmodified form showed more than 80% adsorption capacity (Garg et al. 2008). In one
study, agricultural waste, such as rise husk, and industrial waste, such as fly ash,
were analyzed for adsorption of heavy metals in electroplating industries. The
obtained result showed that rice husk was effective in the simultaneous removal of
iron, leads, and nickel, while fly ash removed cadmium and copper. This study concluded that the percentage of heavy metal removal is affected by many factors
including dose adsorbent, contact time, and optimum pH range (Fan et al. 2017).
8 Agricultural Waste Absorbents for Heavy Metal Removal