Md. Abul Hashem

Automated determinations of selenium in thermal power plant wastewater by sequential hydride generation and chemiluminescence detection.

After the Fukushima disaster, power generation from nuclear power plants in Japan was completely stopped and old coal-based power plants were re-commissioned to compensate for the decrease in power generation capacity. Although coal is a relatively inexpensive fuel for power generation, it contains high levels (mgkg(-1)) of selenium, which could contaminate the wastewater from thermal power plants. In this work, an automated selenium monitoring system was developed based on sequential hydride generation and chemiluminescence detection. This method could be applied to control of wastewater contamination. In this method, selenium is vaporized as H2Se, which reacts with ozone to produce chemiluminescence. However, interference from arsenic is of concern because the ozone-induced chemiluminescence intensity of H2Se is much lower than that of AsH3. This problem was successfully addressed by vaporizing arsenic and selenium individually in a sequential procedure using a syringe pump equipped with an eight-port selection valve and hot and cold reactors. Oxidative decomposition of organoselenium compounds and pre-reduction of the selenium were performed in the hot reactor, and vapor generation of arsenic and selenium were performed separately in the cold reactor. Sample transfers between the reactors were carried out by a pneumatic air operation by switching with three-way solenoid valves. The detection limit for selenium was 0.008 mg L(-1) and calibration curve was linear up to 1.0 mg L(-1), which provided suitable performance for controlling selenium in wastewater to around the allowable limit (0.1 mg L(-1)). This system consumes few chemicals and is stable for more than a month without any maintenance. Wastewater samples from thermal power plants were collected, and data obtained by the proposed method were compared with those from batchwise water treatment followed by hydride generation-atomic fluorescence spectrometry.

Measurements of arsenite and arsenate contained in mining river waters and leached from contaminated sediments by sequential hydride generation flow injection analysis.

In this work, a new analytical method for gasifiable compounds based on sequential hydride generation flow injection analysis (SHGFIA) was applied to water analysis and leaching investigation. For water analysis, it was confirmed that 1 μg L(-1) As(III) and As(V) were stable for a few days when EDTA was added in the sample waters. Dissolved As(III) and total arsenic (As(III)+As(V)) were converted to AsH(3) in neutral and acidic medium, respectively, to transfer to a miniature gas scrubber (100 μL in absorber volume). The collected arsenic was successively measured by flow analysis based on molybdenum blue chemistry. With this system, changes in As(III) and As(V) concentrations of water placed with arsenic-contaminated-sediment was monitored in near real time. From these data, kinetic analyses were carried out and kinetic constant was obtained from plot of ln{(C(∞)-C)/C(∞)} where C and C(∞) were leached arsenic concentration and its final concentration, respectively. It was found that rate of As(III) leaching was much faster than that of As(V) while As(V) leached more in amount compared to As(III). In this work, it was demonstrated that kinetic investigation is also one of the important application of flow analysis. The SHGFIA system showed excellent performance for leaching analysis of arsenic with discrimination of As(III) and As(V).

Investigation of arsenic removal in batch wise water treatments by means of sequential hydride generation flow injection analysis

Arsenic water pollution is a big issue worldwide. Determination of inorganic arsenic in each oxidation state is important because As(III) is much more toxic than As(V). An automated arsenic measurement system was developed based on complete vaporization of As by a sequential procedure and collection/preconcentration of the vaporized AsH(3), which was subsequently measured by a flow analysis. The automated sensitive method was applied to monitoring As(III) and As(V) concentrations in contaminated water standing overnight. Behaviors of arsenics were investigated in different conditions, and unique time dependence profiles were obtained. For example, in the standing of anaerobic water samples, the As(III) concentration immediately began decreasing whereas dead time was observed in the removal of As(V). In normal groundwater conditions, most arsenic was removed from the water simply by standing overnight. To obtain more effective removal, the addition of oxidants and use of steel wools were investigated. Simple batch wise treatments of arsenic contaminated water were demonstrated, and detail of the transitional changes in As(III) and As(V) were investigated.

Hair burning liming in tanneries: a potential sulfide source to the environment

In tannery, liming is the first and indispensable chemical operation where raw hides/skins are treated with sodium sulfide and calcium hydroxide. Liming process releases wastewater containing soluble sulfide in the effluent. In this study, soluble sulfide in the wastewater was estimated during hair burning liming process in the tannery. The soluble sulfide content in liming wastewater was determined by titrimetric method following the official methods of analysis of Society of Leather Technologist and Chemists. It was estimated that, in Bangladesh, yearly 208–623 metric ton soluble sulfide is discharged only from the cowhide processing during hair burning liming process. The sulfide has an adverse impact on the environment including water bodies, atmosphere, land, and plant. Liming wastewater mixing with lower pH wastewater releases hydrogen sulfide gas which has negative effects on the human health and atmosphere. Tanner should use the alternative unhairing methods, e.g., enzymatic, sweating for the cleaner production.

Chromium from tannery waste in poultry feed: A potential cradle to transport human food chain

Abstract Raw skin trimmings (RST), wet blue shaving dusts (WSD), and low-chrome wet-blue scraps (LCWS) are protein-rich tannery wastes which are used as one of the main ingredients for manufacturing of poultry feeds. These feeds may contain toxic chromium, which accumulates in the poultry and cause chrome contamination in human food chain. It is a major concern for humans consuming these poultry as part of their regular diet. In this study, tannery wastes, 12 brands of poultry feeds, broiler chickens (Gallus gallusdomesticus) nourished on chrome containing feed were collected for the investigation of total chromium present and circulated through the process of ingestion and digestion. The chromium content of RST and all poultry feed samples were found to be below 0.03 mg/kg, except the samples of WSD, LCWS, starter feed (FS10), and grower feed (FS11), which were 29854.4 ± 0.9, 14902.0 ± 1.01, 618.3 ± 0.9 and 3.02 ± 0.07 mg/kg, respectively. The chromium in protein concentrate made from WSD and LCWS were 21535.4 ± 1.01 and 13421.8 ± 0.04 mg/kg, respectively. Various body parts of chickens were found to be contained the element in the range of 0.42 to 0.84 mg/kg. Hence, there is a potential human health risk through consumption of contaminated poultry meat as it exceeded the daily adequate intakes (AIs) level.

Chromium Removal from the Tannery Wastewater Using Indigenous Adsorbent

Tannery is recognized as high-strength waste-generating industry. In tannery, leather processing involves a series of chemical treatments and mechanical operations to attain the prescribed characteristics. Inapt disposal of solid and liquid waste from the tannery cause a serious environmental pollution. Chromium containing wastewater is generated from chrome tanning operation which is the most hazardous pollutants released to the environment. Treatment of highchromium-containing wastewater is a major concern in leather processing. In this study, indigenous adsorbent was investigated to remove the metals, especially chromium from the chrome tanning wastewater. The prepared adsorbent was directly mixed with chrome tanning wastewater. Various parameters such as adsorbent dose and contact time were optimized in batchwise technique. The maximum removal of chromium was attained 99.9%. The use of indigenous adsorbent for the removal of chromium could be better instead of conventional methods.