Heavy metal removal from industrial effluent using bio-sorbent blends

Abstract

There is extensive literature on the use of adsorbents derived from waste to treat industrial effluents containing heavy metal ions. However, there is limited information on the use of adsorbent blends. This is applicable for treating effluents which contain a number of heavy metals, so any one single adsorbent may not be suitable for achieving high percent removal of all ions. The present work employs adsorbent blends to treat an electrochemical effluent in batch mode. This work aims to provide valuable insights on the interaction of heavy metals with the adsorbents in blends. Effluent from an electrochemical industry was treated with blends of calcium bentonite, fly ash and wheat bran in different compositions to remove heavy metal ions (Fe, Ni, Cu, As, Zn, Cd) from an aqueous effluent solution. The optimal set of conditions identified were pH, 5-7; contact time, 60-90 min; agitation speed of 200 rpm; adsorbent dosage of 1 g/50 mL; and particle size of 150-300 μ. Metal ions arsenic, zinc and cadmium were completely removed. The percentage removal of (Fe, Ni, Cu) metal ions was in the order Fe(II)(96.73%) > Ni(II)(74.03%) > Cu(II)(70.70%) at optimum conditions in a short equilibrium time of 90 min. Batch experiments were conducted to determine the factors such as adsorbent composition, temperature, pH, agitation speed, dosage, contact time and particle size affecting adsorption, and all these parameters were found to strongly influence the adsorption. Experimental data were analyzed for Langmuir and Freundlich isotherms. Langmuir isotherm shows the maximum adsorption capacities were in order Fe(II)146.1 mg/g > Ni(II) 115.9 mg/g > Cu(II) 74.5 mg/g. Freundlich parameter 'n' was found to be greater than 1 which showed that the adsorption is feasible for all three metals. Freundlich isotherm fit the data comparatively better, but neither of the two isotherms satisfactorily explained the adsorption, which indicated heterogeneity of adsorption. Kinetic studies were performed and analyzed for pseudo-first-and pseudo-second-order kinetics and the Weber-Morris intraparticle diffusion model. The adsorption data fit accurately to pseudo-second-order kinetic model with coefficient of correlation values greater than 0.99 for all three heavy metals. The kinetic constants were found to be 8.49 * 10 −3 , 5.82 * 10 −3 , 5.27 * 10 −3 g mg min for Fe(II), Ni(II) and Cu(II), respectively. From the intraparticle diffusion model, it was inferred that there were different rate-limiting steps during the duration of the adsorption process, including intraparticle diffusion and boundary layer diffusion.

Valorization of Groundnut Shell Biomass for Biosorption of Hexavalent Chromium from Aqueous Solution

“…The findings of this study demonstrate that the adsorption of chromium (VI) ions onto groundnut shell-based biomass is most rapid with an excess of binding sites and gradually slows down as the proportion of binding sites declines. This is similar to the trends observed by other researchers who discovered that most adsorption occurred in the first 35 minutes of exposure of the biosorbent to industrial effluent (Sreedhar & Reddy 2019;Ahamad et al, 2019). At low metal ion loads, adsorption involves high-energy sites.…”

Synthesis and characterization of ground biochar (GB) reinforced composites for removal of heavy metal from palm oil mill effluent (POME)

“…Adeleke et al (2017) demonstrated this claim by observing a decreasing pattern of heavy metal uptake as activated carbon content increases. Sreedhar and Reddy (2019) also noticed a similar decreasing trend of adsorption capacity when the adsorbent dosage was increased. The effect is probably due to the concentration gradient and increased blockage of available active sites caused by the agglomeration of GB particles that reduces the specific surface area of the sample.…”

“…Adding a high dosage of ground biochar pine sawdust during sample preparation provides more potential for treating POME as a higher tendency of heavy metal ions adhered to the free pore sites, allowing a greater adsorption rate. However, a few researchers have argued that further increasing the weight percentage of adsorbent will not further influence the removal percentage of heavy metals as it has already reached saturation (Pertile et al 2021;Sreedhar and Reddy 2019;Gupta et al 2021). Adeleke et al (2017) demonstrated this claim by observing a decreasing pattern of heavy metal uptake as activated carbon content increases.…”

Metal Removal from Nickel-Containing Effluents Using Mineral–Organic Hybrid Adsorbent

“…The percent of Ni(II) adsorbed by coir pith from an effluent containing 145 mg/L of Ni(II) was 88% at 5% (w/v) adsorbent dosage and a further increase in sorbent dosage did not increase nickel removal [ 43 ]. The low rate of Ni(II) removal with the increase in sorbent dosage can be explained by sorbent particle agglomeration, which reduces the specific surface area and increases the diffusion path length [ 44 ]. In batch experiments, it was shown that with the increase in Ni(II) concentration in solution, its removal significantly decreases from 90% at Ni(II) concentration 10 mg/L to 28% at Ni(II) concentration in solution 100 mg/L.…”