Kinetics of cadmium, chromium, and lead sorption onto chemically modified sugarcane bagasse and wheat straw.

In this study, cadmium (Cd), chromium (Cr), and lead (Pb) adsorption potential of unmodified and modified sugarcane bagasse and ground wheat straw was explored from aqueous solution through batch equilibrium technique. Both the materials were chemically modified by treating with sodium hydroxide (NaOH) alone and in combination with nitric acid (HNO3) and sulfuric acid (H2SO4). Two kinetic models, pseudo-first order and pseudo-second order were used to follow the adsorption process and reaction fallowed the later model. The Pb removal by both the materials was highest and followed by Cr and Cd. The chemical treatment invariably increased the adsorption capacity and NaOH treatment proved more effective than others. Langmuir maximum sorption capacity (q m) of Pb was utmost (12.8-23.3 mg/g of sugarcane bagasse, 14.5-22.4 mg/g of wheat straw) and of Cd was least (1.5-2.2 mg/g of sugarcane bagasse, 2.5-3.8 mg/g of wheat straw). The q m was in the order of Pb > Cr > Cd for all the three adsorbents. Results demonstrate that agricultural waste materials used in this study could be used to remediate the heavy metal-polluted water.

Assessment of physicochemical parameters of wastewater samples.

Water samples from selected locations of Nullah Lai and Koh-e-Noor textile mill in the metropolitan city of Rawalpindi and Islamabad, Pakistan, were collected. Physicochemical parameters and heavy metals were determined using standard analytical procedures in comparison with sites, locations and subsequent interval of 3 months. The results of the physicochemical analysis at different locations of Nullah Lai and Koh-e-Noor textile mill with an interval of 3 months were obtained in the following range: pH (7.16-8.29), temperature (17.8-28.8 °C), conductivity (1,005-3,347 µS/m), TDS (754.3-2,519.5 mg/L), turbidity (272.8-487.05 NTU), total hardness (300-452 mg/L), nitrates (10.11-22.95 ppm), calcium (74.31-139.2 ppm), chloride (127.72-396.16 ppm), sulphate (15.97-87.38 ppm), NaCl (210.5-631.1 ppm), Ni (0.30-0.72 ppm), Cd (0.005-0.03 ppm), Cr (0.2-7.4 ppm), Pb (0.12-0.73 ppm), Zn (0.03-0.08 ppm) and Cu (0.01-0.06 ppm). The highest value of physicochemical parameters (compared with Nullah Lai) was obtained in locations of Koh-e-Noor textile mill. The results obtained exceeded the maximum allowable limit set by the World Health Organization for drinking purpose but can be used for irrigation purposes after suitable treatment and purification.

Metal contamination of vegetables grown on soils irrigated with untreated municipal effluent.

Metals in soils and vegetables irrigated with untreated municipal/industrial effluent, from four cities of Pakistan (Gujranwala, Sialkot, Hyderabad and Mirpurkhas) were assessed. The cadmium, copper, lead and chromium concentrations in the municipal/industrial effluent from all sites were above the recommended permissible limits. Similarly, cadmium, lead and nickel concentrations in almost all the soil samples were above the recommended permissible limits with chromium higher than the recommended permissible limits in 62% soils and copper higher in 26%. Cadmium and chromium concentrations were above the recommended permissible limits in all the examined vegetables and lead was exceeded in 90% of vegetables.