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Water quality in the aquatic body of Dhaka Export Processing Zone (DEPZ) area was studied on the basis of some physiochemical parameters and heavy metal concentrations. Physiochemical parameters like pH, Electrical Conductivity (EC), Chemical Oxygen Demand (COD), Total Dissolved Solids (TDS) and concentrations of some heavy metals like As, Cd, Cu, Co, Cr, Fe, Mn, Ni, Pb, Hg and Zn were measured. Among different physiochemical parameters, pH, TDS and EC were found within the range. The range of pH for all of the samples was found from 7.1 to 8.17 and 120 to 450 mg/L for TDS. The Values of EC were found from 90 to 300 µs cm-1. For pH, EC and TDS, though the ranges were within the limits but there was an increasing trend of the values was observed in every case which is highly alarming. The range of COD values was estimated from 90 to 300 mg/L and in most of the samples the values exceeded the standard range. The heavy metal containments of the surface water indicated that the concentrations of Cr, Cu, Ni, Zn, Hg and As were obtained below the permissible limit, detection by WHO, 1996. On the other hand, concentrations of Cd, Co, Fe, Pb, Mn and Hg were exceeded the permissible limits. Correlation matrix shows a significant correlation among Pb, Cu, Co, Mn and Fe. Enrichment factor shows high concentrations of Cd, Cr and Hg. Stated environmental condition is highly vulnerable for human being, that's why this is the time to take proper steps for remediation and preventing the pollution around DEPZ water body which is directly related to the industrial emission of DEPZ.
Thermodynamic dissociation constants (Ka) of propionic acid in 0, 5, 10 and 20 wt% 1propanol-water binary mixtures have been determined between 303.15 and 323.15 K. A conductometric method has been applied to measure the molar conductance of dilute solutions of propionic acid. Fuoss-Kraus conductance equation has been applied to calculate the values of limiting molar conductance (Λ0) and thermodynamic ionization constant (Ka). It was found that both the values of Ka and Λ0 decreased by the increasing of amount of 1-propanol in the binary mixtures. However, Ka values were decreased and Λ0 values were increased by increasing temperatures. The normalized Walden products of the propionic acid have been calculated. Thermodynamic quantities such as change of standard free energy (∆G°), change of standard enthalpy (∆H°) and change of standard entropy (∆S°) have been calculated in case of each of the binary mixtures.
Copper ions (Cu(II)) produced from various industries can lead to pollution at toxic levels, eventually finding its way into food chains and resulting in serious health impairment.Among different treatment technologies practiced, adsorption is unique in terms of its versatility and economic feasibility.Here, the removal of Cu(II) was examined using chitosan-nano zero valent iron-activated carbon (CS-NZVI-AC) composite beads.Results indicate that the rate of Cu(II) adsorption onto the CS-NZVI-AC accelerated significantly in comparison with lonechitosan (CS), activated carbon (AC) and zero valent iron (NZVI).Moreover, the hybridization of CS-AC with NZVI endows an increase in the uptake of Cu(II) up to 30% compared to that of CS-AC alone.The adsorption mechanism is understood as chemisorptions along with the active Van der Waals forces, as supported by the best fit of sorption data with pseudo-second order kinetics and Freundlich isotherm model.The adsorption capacity of CS-NZVI-AC for Cu(II) increased with increasing pH of up to 5 and with 25°C water temperature.Thus, it is indicated that this hybrid CS-NZVI-AC composites have great potential for environmental remediation efforts for Cu(II) and other similar heavy metal ions.
