How many grams of copper will be produced by adding 10 g of sulfuric acid to the zinc husks that will produce CuO?
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Answer:
This review examines a variety of adsorbents and discusses mechanisms, modification methods, recovery and regeneration, and commercial applications. A summary of available researches has been composed by a wide range of potentially low-cost modified adsorbents including activated carbon, natural source adsorbents (clay, bentonite, zeolite, etc.), biosorbents (black gram husk, sugar-beet pectin gels, citrus peels, banana and orange peels, carrot residues, cassava waste, algae, algal, marine green macroalgae, etc.), and byproduct adsorbents (sawdust, lignin, rice husk, rice husk ash, coal fly ash, etc.). From the literature survey, different adsorbents were compared in terms of Zn2+ adsorption capacity; also Zn2+ adsorption capacity was compared with other metals adsorption. Thus, some of the highest adsorption capacities reported for Zn2+ are 168 mg/g powdered waste sludge, 128.8 mg/g dried marine green macroalgae, 73.2 mg/g lignin, 55.82 mg/g cassava waste, and 52.91 mg/g bentonite. Furthermore, modification of adsorbents can improve adsorption capacity. Regeneration cost is important, but if consumption of virgin adsorbent is reduced, then multiple economic, industrial, and environmental benefits can be gained. Finally, the main drawback of the already published Zn2+ adsorption researches is that their use is still in the laboratory stage mostly without scale-up, pilot studies, or commercialization.
1. Introduction
Water is a source of energy and life, although millions of people worldwide are suffering from the shortage of clean drinking and fresh water. Rapid pace of population expansion, industrialization, and unplanned urbanization have largely contributed to the severe water pollution and surrounding soils. Discharge of toxic industrial wastes and untreated sanitary, dumping of industrial effluent, and runoff from agricultural fields can be the main sources of freshwater pollution. It is well known that 70 to 80% of all illnesses in developing countries are related to water contamination, particularly susceptible children and women [1].
Contamination of aqueous environments by heavy metals is a worldwide environmental problem due to their toxic effects and accumulation through the food chain [2]. The major pollutants are heavy metals in ground, marine, industrial, and even treated wastewaters [3]. The presence of heavy metals in drinking water will be hazardous to consumers. Zn, Cd, Hg, Pb, Cr, Cu, and so forth can damage liver and nerves and block functional groups of vital enzymes and bones [4]. Metal ions in water can occur naturally from anthropogenic sources and from leaching of ore deposits, which mainly include solid waste disposal and industrial effluents. The levels of heavy metals in water system have substantially increased over time with rapid development of industrial activities [5].
Various regulatory bodies have set the maximum prescribed limits for the discharge of toxic heavy metals in the aquatic systems. However the metal ions are being added to the water stream at a much higher concentration than the prescribed limits by industrial activities, thus leading to health hazards and environmental degradation (Table 1) [6]. In Malaysia, the discharge of heavy metals to the water bodies should be stipulated to the limits of standard A and B according to the Environmental Quality (Sewage and Industrial Effluents) Regulations, Environmental Quality Act 1974 [7].