Chromium is well-thought-out heavy metal which is one of the enormously lethal due to its cancer-causing nature. In this study, iron oxide is used as adsorbent for chromate removal from aqueous solution as a function of pH, time, temperature, concentration of adsorbate and media dosage. The influence of pH on Cr (VI) sorption by iron oxide reveals that adsorption is significantly increased as pH is decreased from 8 to 2. The sorption rate is detected to be higher in the beginning and then it remains constant after 120 min of equilibrium time. The removal of Cr (VI) is found to be greater at higher temperature, which confirms the endothermic nature of Cr (VI) adsorption by iron oxide. Whereas, the kinetic investigations confirm that the chromate adsorption follows the pseudo second order with kinetic energy in the range of 8.4–83.7 kJ mol−1.

Agricultural waste based low cost oxidized activated carbon (OSD) and un-oxidized activated carbon (USD) samples were prepared from saw dust of Ziziphus jujube by chemical activation with phosphoric acid (H 3 PO 4 ). The activated carbon was used for the removal of toxic metal ions such as cadmium(II) and lead(II) from aqueous solutions. The effect of pH (2-9), initial concentration (70-100 mg/L), contact time (5-700 min), activated carbon dose (0.1-1.0 g) and temperature (298-328 K) was investigated. In addition, the kinetic study was performed at pH 6, while the carbon dose of 0.1 g was used for 40 mL solution of 70 mg/L at four different temperatures (298, 308, 318 and 328 K). The adsorption efficiency of USD was found higher than OSD. Comparatively higher uptake of Pb(II) ions was observed by each carbon sample. Pseudo-second order equation best fitted the experimental data. As such, both activated carbon samples (USD and OSD) exhibited higher adsorption capacities and faster kinetics which revealed their commercial usefulness.

The present study focused on the physicochemical characterization and spectrophotometric determination of the concentrations of trace elements (Zn, Cu, Fe and Mn) and toxic heavy metals (Cd and Pb) in raw milk samples collected from various commercial sites of Peshawar city, Pakistan. Evaluation of the nutritional values as well as the possible health concerns associated with the consumption of contaminated milk shown the average percentage composition of protein, fats, solid non-fats, lactose, salts and added water in the milk sample as 2.78, 4.81, 6.41, 3.05, 0.47 and 31.1 %, respectively. The values of pH, conductivity, density and freezing point were observed as 6.59, 3.51 mS/cm, 1.04 g/mL and -0.3674 ºC at 26 ºC. The physicochemical characteristics such as percentage protein, fat, lactose, salts, water, solid not fat, total solids, pH, conductivity and density were evaluated and found in the safe limits of the WHO/FAO. The average concentration of trace elements such as zinc and copper were found to be 1.4035 mg/L and 0.2588 mg/L, respectively. The concentration of Zn and Cu was found within permissible limits suggested by WHO. However, the average concentration of Fe, Mn, Cd and Pb were found higher than the permissible limits of WHO. The observed concentrations were: Fe = 1.5553, Mn = 0.4354, Cd = 0.1865 and Pb = 1.1162 mg/L. The presence of the non-essential and hazardous Cd and Pb in milk samples even in lower concentrations may cause severe health problems since these are the most noxious pollutants due to their non-biodegradable and bio-accumulative nature. Over-dose of Fe and Mn also leads to several health issues. A thorough and more precise investigation of raw milk consumption in Peshawar is highly recommended to ascertain the actual reasons and sources in the larger public interests.

Water decontamination from chromium (Cr) is of prime importance because of its carcinogenic nature. The sample of activated carbon was characterized by surface area analyzer, SEM/EDX, TGA, FTIR and PZC. This study was focused on adsorption of hexavalent chromium from the aqueous phase onto activated carbon. Both the temperature and pH had a positive effect on the chromate uptake by activated carbon. The chromate uptake at different pH values followed the trend: pH 2 > pH 3 > pH 4 > pH 5 > pH 7 > pH 8. The sorption maxima at pH 2 was explained on the basis of electrostatic attraction between the negatively charged chromate anions and positively charged surface of the activated carbon. Different models were tested to access the sorption maxima and to probe into the chromate adsorption mechanism. The thermodynamic parameters suggested that heat is needed to shift the hexavalent chromium from solution to the solid surface. It was concluded that the anion exchange sorption was involved in removing the chromate anion from the aqueous system into the surface of activated carbon.