An environmental pollution is the unfavorable alteration of surrounding toxicity due to heavy metals, organic pollutants, radioactive materials, pesticides, dyes, pigments, fatty/ oil impurities and minerals that are responsible for crucial ecological and health concerns. The indiscriminate industrial and anthropological activities render water resources unsuitable for consumptions. Percolations of synthetic pollutants in water are responsible for detrimental effects on aquatic flora and fauna. Environmental contamination of water poses the major challenge to develop efficient water treatment techniques based on usage of biopolymers. Hence, chitosan (de-acetylated chitin: β-(1 → 4) D-glucosamine) biosorbent is preferred which is cheap, biodegradable, and biocompatible for the mitigation of few heavy metals from water. Chitosan's flexible skeleton was modified by doping few organic/inorganic moieties to yield biocomposites for adsorption of varied pollutants. In this chapter, the batch adsorption of toxic Pb (II) ions from water using graphite doped chitosan composite (GDCC) as an adsorbent is discussed. Maximum Pb (II) ions adsorption capacity was 6.711 mg/g (from Langmuir) at optimum pH 6 with dosage of 1 g/L in 120 min. Biosorption mechanism is emphasized in context with wastewater cleanup procedures.

Wustite (FeO)−spinel (magnetite, Fe 3 O 4 /maghemite, γ-Fe 2 O 3 ) core−shell iron oxide nanoparticles (IONPs) of shapes cuboctahedron, cube, and octopods were successfully synthesized by thermal decomposition of an iron oleate precursor conducted using a bulky coordinating solvent, tri-n-octylamine in the presence of oleic acid. The shape of particles was kinetically controlled by varying the aging time of particles at the reaction temperatures 320, 350, and 365 °C. With increasing reaction temperatures, we find that the particle shape evolves from a cuboctahedron to a cube to an octopod. To explain the shape transition, we propose the formation mechanisms of differently shaped particles at these reaction temperatures by accounting the relative rate of iron oxide monomer deposition onto the {111} facets over surface diffusion of the deposited monomers majorly toward {100} facets of the growing crystals. We elucidate that at increasing temperatures, the monomer deposition rate increases over the surface diffusion rate, which leads to the shape transition. Further, we propose the growth mechanisms of differently shaped particles at these temperatures based on the estimated timescales of growth events such as diffusion-controlled growth, Ostwald ripening growth, and Brownian coagulation growth in comparison to the experimental aging time. We find that at 320 °C, the coagulation growth time scale is large as compared to the experimental aging time; hence, particles at 320 °C grow via diffusion-controlled growth and Ostwald ripening growth events. In contrast, at 350 and 365 °C, the coagulation growth timescales are smaller than the experimental aging time, and the particles grow via all of the growth events. The present work provides insights into the understanding of largesized differently shaped IONPs formed in the thermal decomposition route either by the coordination of the reaction solvent or chemical additives (capping agents) to the specific facet of growing crystals.

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