This review summarizes the progress made, in the field of low-cost biosorption of heavy metal ions, over the past few years. It gives a comprehensive summary of the synthesis, performance, modification and regeneration of biosorbent. The review also focused upon optimum operating parameters, isotherm and kinetic studies. Moreover, from an industrial application point of view, fixed-bed column studies have been discussed in this paper. Methods like chemical pretreatment, grafting, immobilization, etc., which improve the biosorbent properties, have been summarized. Operating parameters that affect the biosorption process such as temperature, pH, contact time, agitation speed, etc. have been studied to understand the relationship between factors and removal efficiency. For most of the studies, biosorption process was found to be endothermic, with room temperature being optimum for the process. Grafting was observed to enhance the adsorption capacity of biosorbent enormously. Biosorption process generally followed Langmuir or Freundlich isotherm, whereas mostly the best fit for kinetic model was pseudo-second-order. Desorption process was mostly carried out via acidic eluent. The performance of biosorbents was observed to be appreciable when they were packed into fixed-bed columns.

A review on valorization of biomass in heavy metal removal from wastewater

Cadmium (Cd) and lead (Pb) contaminations are disturbing environmental issues, which causes serious harm to aqueous systems and human health. Therefore, removing them from aqueous solution is essential to prevent its damage to the environment. Environmental adsorption research as one solution has seen a boom over the past decade. Using modified biochar has proved to be more suitable for the adsorption of cadmium and lead. Most of the studies apply a routine method such as kinetic and isotherm modelling to demonstrate the macroscopic trend of adsorption, often without elaborative evaluation of the effectiveness and characteristics of the models. This review compiles different adsorption kinetics and isotherms models and also presents their origins, modified versions, and their applicability in the liquid adsorption situation. The effect of experimental parameters and adsorption mechanisms are discussed to study the adsorption performances of modified biochar. The adsorption mechanism was majorly by surface precipitation, ion exchange, electrostatic attraction, complexation and physical adsorption. The adsorption was majorly endothermic and spontaneous. Additionally, preparation and regeneration of modified biochar are also presented to provide a direction for sustainable improvement. This paper summarizes with a note on challenges, prospects and future perspectives of adsorption of cadmium and lead pollutions.

Adsorption of cadmium and lead from aqueous solution using modified biochar: A review

Cadmium (Cd) and lead (Pb) contaminations are disturbing environmental issues, which cause serious harm to aqueous systems and human health. Therefore, removing them from aqueous solution is essential to prevent their damage to the environment. Environmental adsorption research as one solution is promising and has been getting a lot of attention in the recent years. Using modified biochar has proved to be more suitable for the adsorption of cadmium and lead. In this review, the sources of cadmium and lead in the environment and their hazards have been elucidated. In addition, the preparation methods of modified biochar to remove Cd and Pb have been discussed. This review also presents the adsorption kinetics and isotherms results for the adsorption of Cd and Pb from aqueous solution using modified biochar. The effect of experimental parameters and adsorption mechanisms are also discussed in order to understand the adsorption performances of modified biochar in great detail. The adsorption mechanisms were surface precipitation, surface complexation, ion exchange, chelation, electrostatic attraction, inner sphere complexation, redox and physical adsorption. The adsorption was mainly endothermic and spontaneous. Additionally, the results on the regeneration of modified biochar are presented to provide a direction for sustainable improvement. Finally, this review article also provides the challenges, prospects and future perspectives of adsorption of cadmium and lead from aqueous solutions using the modified biochar. 

Review on adsorptive removal of metal ions and dyes from wastewater using tamarind-based bio-composites

Biosorption is a very effective technique to eliminate the heavy metals present in the wastewater that utilize nongrowing biomass. The adsorption ability of the Periyakulam-2 (PKM-2) variety of Moringa Oleifera leaves (MOLs) to eliminate Pb(II) and Zn(II) ions from an aqueous solution was examined in this work. Fourier transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy, energy-dispersive X-ray (EDX) analysis, X-ray powder diffraction, and Brunauer-Emmett-Teller methods were used to characterize the PKM-2 variety of MOLs. The set of variables consists of the metal ion initial concentration, a dosage of the adsorbent, and pH were optimized with the help of the response surface methodology to get maximum metal removal efficiency of lead and zinc metals using the PKM-2 MOL biosorbent. A maximum Pb(II) removal of 95.6% was obtained under the condition of initial concentration of metal ions 38 mg/L, a dosage of the adsorbent 1.5 g, and pH 4.7, and a maximum zinc removal of 89.35% was obtained under the condition of initial concentration of metal ions 70 mg/L, a dosage of the adsorbent 0.6 g, and pH 3.2. The presence of lead and zinc ions on the biosorbent surface and the functional groups involved in the adsorption process were revealed using EDX and FTIR analysis, respectively. The adsorption data were evaluated by employing different isotherm and kinetic models. Among the isotherm models, Langmuir's isotherm showed that the best fit and maximum adsorption capacities are 51.71 and 38.50 mg/g for lead and zinc, respectively. Kinetic studies showed accordance with the pseudo-second-order model to lead and zinc metal adsorption. Thermodynamic parameters confirmed (ΔG° 0) that the sorption mechanism is physisorption, exothermic, spontaneous, and favorable for adsorption. The results from this study show that the MOL of the PKM-2 type is a promising alternative for an ecofriendly, low-cost biosorbent that can effectively remove lead and zinc metals from aqueous solutions.

Central Composite Design for Adsorption of Pb(II) and Zn(II) Metals on PKM-2 Moringa oleifera Leaves.

In the present study, biosorption capacity of Tamarindus indica is investigated for removal of lead and zinc. The heavy metals, namely lead and zinc, are successfully removed from aqueous solution by batch biosorption using Tamarindus indica as biosorbent. The removal percentage of selected metals, namely lead and zinc, was improved through optimization of variables using response surface methodology (RSM). The conditions obtained with RSM are agitation time of 47.65 min, initial metal ion concentration of 46.49 mg/l, biosorbent dosage of 1.23 g and pH of 7.64 for lead biosorption, whereas those for zinc are agitation time of 22.84 min, dosage of 0.78 g, initial ion concentration of 20.87 mg/l and pH of 6.98. The maximum of 83.52% removal of lead was achieved and for zinc 63.7%. Heavy metal biosorption ability of biosorbent has been qualitatively characterized using Fourier transform infrared spectroscopy and scanning electron microscopy analysis. This study reveals that the Tamarindus indica efficiently removes heavy metals. The biosorption kinetic study at RSM optimized conditions exhibited better fit to Freundlich isotherms (R2 0.993) for lead than Langmuir isotherm (R2 0.974).

Removal of multiple metals using Tamarindus indica as biosorbent through optimization of process variables: a statistical approach

Lysine is an essential amino acid utilised in diverse industrial areas, mostly as animal feed and food. It is synthesized by various organisms but the novel Corynebacterium glutamicum (gram positive, non sporulating bacteria) is selected anticipating to the enormous research. This research has paved a way towards enhancing the lysine productivity. Different strains of Corynebacterium glutamicum utilised many technologies for the enhanced production of L-Lysine. This literature study examines the current status of L-lysine industrial production with a focus on technology used for development irrespective of the strain and fermentation technologies through different approach of understanding of provisions (NADPH, Media source, PTS, exploit of RAM, Vector systems and promoters) with use of different methodologies. The technologies were divided into metabolic engineering, conventional gene mutations, optimization of fermentation parameters (RSM, ANN, GA), gene overexpression, gene switching and exploit of CRISPR, electric current. This review presents the methodologies which are superior at manufacturing enhanced amounts of lysine and report the techniques which assist in producing the best yield in collation with the earlier. This also focuses on the genes related to lysine export and provides conviction of utilizing lysine as an animal feed.

E. Rajeswara Reddy

Papers

Removal of multiple metals using Tamarindus indica as biosorbent through optimization of process variables: a statistical approach

Recent Advances in engineering Corynebacterium glutamicum for production of Lysine