As a result of quick industrialization and urbanization, water contamination is one of the most serious menaces humanity face. Water contamination concerns all populations, living species, and the ecosystem that living in the waters. Among the diverse aqueous pollutants, heavy metals are regarded to be one of the most dangerous contaminant due to the difficulty of their removal from water system (not biodegradable nature and mobility)(Campos et al. 2020; Das and Mishra 2020; Meseldžija et al. 2020). Heavy metals are extensively employed in many domains industry, such as metal plating, leather, petrochemical, paper and pulp, agriculture activities, municipal wastewater and other environmental and global changes.
The aim of environmental research has extensively been focused on municipal or industrial wastewater due to the potential impact to humanity. Industrial and municipal wastewater contains different toxic heavy metals namely chromium, mercury, silver, lead, copper, cadmium, zinc, iron, arsenic, and the platinum group elements (Das and Mishra 2020; Kaya et al. 2020; Vunain, Kenneth, and Biswick 2017). Pouring these components into the surroundings provokes water and soil contamination. Among the above-mentioned metals, copper and iron are the most earth plentiful, making up about 0.006% and 5.63% of the earth’s crust, respectively (Das and Mishra 2020).
The both presence of iron and copper ions can be observed in the most abundant and widely used materials notably in the smelting procedures, agro-chemicals, mining, electronic and electrical industries, traffic, mechanical manufacturing industry, steel and iron industry units, and architecture (Campos et al. 2020). Low concentration of iron and copper can be found in all natural water sources (Khatri, Tyagi, and Rawtani 2017). Nevertheless, when consumable water is stagnated for a long moment in household pipes in copper or iron, the concentration of these components may increase due to leaching of the pipes. it is well documented that copper ion levels in consumable water frequently rise during distribution, particularly in systems with heavy carbonate water along being an alkaline pH or an acidic pH (Vunain et al. 2017). Copper and iron are indispensable to human health but like other heavy metals ions, they can cause negative effect at high level. The maximum allowable limit of Fe and Cu in consumable water are 0.3 mg/L and 2 mg/L, respectively (Khatri et al. 2017; Wang et al. 2020). Increasing the level of these metals in the water raises a grave problem to mankind as they are toxic and non-degradable. Indeed, permanent consumption of such water with high concentrations of iron may result in a condition namely iron overload (Zheng et al. 2017). In addition, excessive of iron in drinking water intake may result in life issues such as heart failure, hypothermia, diabetes, deterioration of hematopoiesis, cirrhosis, liver damage, etc (Kaveeshwar et al. 2018; Tumampos et al. 2021). It can be even associated to different operational issues namely color, odor, and staining of laundry, bad taste, making the water unserviceable for aesthetic considerations (Das and Mishra 2020; Khatri et al. 2017). Regarding copper, it dangerousness may result to harsh mucosal irritation, capillary damage, renal damage, central nervous issues, gastrointestinal problems, depression, liver and kidney damage (Fotsing et al. 2020; Vunain et al. 2017; Wang et al. 2020). Consequently, all of these trepidations necessitated urgent attention, which has incited researchers to attenuate the concentration of Fe and Cu contamination. Several remediation methods namely ultrafiltration (Aloulou et al. 2020), electrocoagulation (Kim, Kim, and Zoh 2020), coagulation flocculation (Sun et al. 2020), advanced oxidation (Liang et al. 2020), and membrane separation (Chen et al. 2020) are used for heavy metal removal. However, these technologies have some drawbacks such as low efficiency, production of secondary sludge, high cost operating cost, and sensitive operating conditions (Kaya et al. 2020; Vunain et al. 2017).
Recently, the utilization of carbonaceous based materials as adsorbents for heavy metals treatment from wastewater has grown an advantageous field for scientific studies (Liu et al. 2018; Maguana et al. 2019; H. Wu, Li, and Liu 2018). Activated carbon is regarded as an effective and eco-friendly adsorbent because it has distinctive structure, well-developed pore volume, large surface area, and important number of active sites to adsorb heavy metal ions (Astuti et al. 2019; Ipeaiyeda, Choudhary, and Ahmed 2018; Peng et al. 2017). Commercial activated carbon is considered as one of the most used adsorbents for eradication of heavy metals from effluent, however it is sometimes limited due to higher cost (Daouda et al. 2019; Kaya et al. 2020). After all, the activated carbon is synthesized from peat, coal, lignite, and wood which is very exhaustible and expensive and is regarded as an inconvenience (Zhang et al. 2017).
Therefore, this situation has guided many researchers to explore cheaper carbonaceous based materials for activated carbon fabrication from cellulose, hemicelluloses and lignin biomass (Jagadeesh et al. 2017; Kalagatur et al. 2017; Li, Zhang, and Liu 2018). Indeed, disposal of agricultural wastes being greatly available such as walnut shell (L. Wu et al. 2018), palm kernel shell and coconut shell (Ipeaiyeda et al. 2018), cotton cakes (Daouda et al. 2019), lemon peel (Meseldžija et al. 2020), pecan shell (Kaveeshwar et al. 2018), corn cob (Campos et al. 2020), xhanthoceras sorbifolia (Zhang et al. 2017), jatropha shell (Habaki et al. 2019) and, rice husk (Roy, Das, and Sengupta 2017), etc. have been studied.
Whereas, in many countries, tons of rice husk and jatropha shell are emerging every year as waste over the world. Cameroon was ranked first among the central African countries having rice industry and the Far-North Region of Cameroon has the highest rice production area and account about 85% of the total production (Goufo 2008). Tons of rice husk are abounding more and more as waste over the country. These waste by-products are utilized as fuel or directly poured in the environment involving it pollution. Thus, conversion of agricultural wastes namely rice husk and jatropha shell for the generation of sustainable carbon based materials is greatly important in order to reduce the pollution of environment. Additionally, it can boost the economy by the conversion of these natural resources efficaciously into some highly value-added by-products. In this present work, the activated carbon was prepared from jatropha and rice husk which was used to adsorb heavy metal ions, including iron and copper present in aqueous solutions.
Activated carbon can be synthetized, by physical or chemical activation, from several carbonaceous materials. The physical activation achieved by high temperature range of 800°C to 1100°C, in inert atmosphere. In the contrast to physical activation, the chemical activation required low temperature and higher product yield comprises one step that requires the impregnation of the raw carbonaceous materials using activating agent such as ZnCl2, NH3, KOH, and H3PO4 (Ipeaiyeda et al. 2018; Li et al. 2018; Liu et al. 2018).
Activated carbon with high surface area and good adsorption capacity of metal ions can be fabricated by H3PO4 activation of several lignocellulosic compounds. Nevertheless, little information is available about the attainment of the production of excellent adsorbents from polyhydric alcohols (organic monomer) and H3PO4 as carbon precursor and activation agent, respectively. It is well documented that alcohols can interact easily with phosphoric acid to form organic phosphates with low polymerization degree. These compound can be decomposed easily at low temperature (about 473 K) (H. Wu et al. 2018). This process is producing a large number of oxidizing agents, which can enhance the carbonization of polyhydric alcohols and raise the oxygen content of the produced carbonaceous based materials (Liu et al. 2015). Therefore, this work is aimed: (1) to evaluate the feasibility of production of functional carbonaceous based materials from jatropha and rice husk and polyhydric alcohols with phosphoric acid activation; (2) to characterize the as synthesized carbon materials; (3) to study the efficiency of the as prepared activated carbon to adsorb heavy metal ions, including iron (II) and copper (II) present in aqueous solutions.