Abstract
Abstract Dried ground roots of water hyacinth (Eichhornia crassipes) were used for removal of Pb(II) from aqueous solution. Batch adsorption experiments were conducted with the dried roots (0.1 g dry weight) using 100 mg/L of Pb(II) aqueous solution adjusted at pH 5.0. Equilibrium was obtained in 90 min with a 92% removal of Pb(II). The effect of contact time, pH, adsorbent dosage, initial metal ion concentration on the adsorption of Pb(II) were also studied. Kinetic studies indicated that the adsorption of Pb(II) followed the pseudo-second-order model with a reaction rate constant (k) of 0.0127 mg/(g.min). Kinetics data conforming to the pseudo-second-order model suggest that chemisorption was the rate-limiting step in the adsorption process. The adsorption data were found to fit best into the Langmuir model (R2 = 0.986). The maximum adsorption capacity was found to be ∼50 mg Pb(II) per g of dried roots. To investigate the feasibility of using the water hyacinth roots in a more realistic situation, wastewaters collected from various sources were also tested with the biosorbent. Significant removal of Pb(II) (∼88% to ∼100%) was observed from the wastewaters at pH 5.0. High adsorption capacity, rapid kinetics, and its low cost make water hyacinth dried roots a good candidate for the removal of Pb(II) from wastewaters.
Highlights
Increasing industrial activities across the globe caused a concomitant increase in the use of heavy metals over the last few decades (Reddy et al 2012)
Heavy metals discharged into aquatic habitats are likely to elevate the level of heavy metal concentrations in microorganisms, flora, and fauna residing in that habitat; these bioaccumulated heavy metals may come along the food chain (Bhuiyan et al 2015)
The results showed that with an increase of dried water hyacinth roots (DWHR) dosage from 0.025 to 0.1 g, the Pb(II) removal increased from 37% to almost 93% (Figure 4)
Summary
Increasing industrial activities across the globe caused a concomitant increase in the use of heavy metals over the last few decades (Reddy et al 2012). There are over 30,000 factories in and around the capital city of Dhaka (Rampley et al 2020) These factories are continuously discharging pollutants in the form of organics, heavy metals, pathogens, etc. Bhuiyan et al (2015) found that chromium, arsenic, lead, and cadmium contents in water and sediment samples of the Buriganga river exceeded critical limits and the permissible limits set by the Bangladesh government. They attributed the elevated concentrations of these metals to industrial activities and urban sewage systems. It is necessary to treat these metal-contaminated wastewaters before discharge to the environment
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