Sustainable natural adsorbents for heavy metal removal from wastewater: lead sorption on pine bark (Pinus radiataD.Don)

Synthesis, characterization and column adsorption properties of gum ghatti and water hyacianth derived cellulose grafted poly(vinyl sulfonic acid-co-acrylamide) composites

Vinylsulfonic acid (VSA), acrylamide (AM) and N, N methylene bis acrylamide(MBA) were copolymerized by radical polymerization in the presence of gum ghatti (GG) and treated water hyacianth (WH) in water. Several composite copolymers were prepared by varying the i) AM: VSA molar ratios ii) wt% of GG and iii) wt% of treated WH based on a Box-Behnken Design(BBD) of a response surface methodology (RSM) model with three input variables and the batch adsorption capacity (mg/g) of 100 mg/L Cd (II) from water as response. The composite polymer was characterized by Fourier transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis(TGA), X- ray photo electron spectroscopy (XPS), compressive strength, pH reversibility, pH at point zero charge (pHPZC), Brunauer-Emmett-Teller (BET) surface area and scanning electron microscopy (SEM). The network parameters of the composites were determined. The copolymer composite prepared with AM: VSA of 5:1 containing 10 wt% GG and 4 wt% treated WH showed an optimum batch adsorption capacity of 399.15 mg/g Cd (II) from water containing 100 mg/L Cd (II). The same composite showed an adsorption capacity of 170.1 mg/g and a removal% of 31.5 at a feed concentration/feed flow rate/bed height of 150 mgL-1/30mLmin-1/30 mm in a fixed bed column.

Batch adsorption studies on surface tailored chitosan/orange peel hydrogel composite for the removal of Cr(VI) and Cu(II) ions from synthetic wastewater

Elimination of heavy metals from wastewater has been a significant process to improve the aquatic source's quality. Various materials act as very effective adsorbents to remove heavy metals, which cause toxicity to plants and all other living organisms. Thus, the present work focuses on removing heavy metals chromium (Cr) and copper (Cu) ions containing wastewater using biodegradable and cost-effective chitosan-based hydrogel composite. The composite was prepared via chemical cross-linking of radical chitosan with polyacrylamide and N,N'-Methylene bisacrylamide and blended with orange peel. The synthesis of the adsorbent has been confirmed by using Fourier-transform infrared spectroscopy (FT-IR), Scanning electron microscopy - Energy dispersive X-ray analysis (SEM-EDAX) and X-ray diffraction (XRD) studies. The adsorption power of the composite of metal ions at different time, pH, adsorbent dosages, different metal ion concentrations were analyzed by using Atomic Absorption Spectroscopy (AAS). The results concluded that the optimum pH for Cr(VI) and Cu (II) were 4 and 5, contact time: 360 min, adsorbent dosage: 4 g, and initial metal ion concentration: 100 mg/L for each metal ions. The adsorption isotherm models follow the Freundlich model and pseudo-second-order kinetics. From the results, the adsorption capacity was observed to be 80.43% for Cr(VI) and 82.47% for Cu(II) ions, respectively.

Inexpensive Organic Materials and Their Applications towards Heavy Metal Attenuation in Waters from Southern Peru

There is interest in using locally available, low cost organic materials to attenuate heavy metals such as Cd, Cr, Cu, Hg, Ni, Pb, and Zn found in surface waters in Peru and other developing regions. Here we mesh Spanish language publications, archived theses, and prior globally available literature to provide a tabulated synthesis of organic materials that hold promise for this application in the developing world. In total, nearly 200 materials were grouped into source categories such as algae and seashells, bacteria and fungi, terrestrial plant-derived materials, and other agricultural and processing materials. This curation was complemented by an assessment of removal potential that can serve as a resource for future studies. We also identified a subset of Peruvian materials that hold particular promise for further investigation, including seashell-based mixed media, fungal blends, lignocellulose-based substrates including sawdust, corn and rice husks, and food residuals including peels from potatoes and avocadoes. Many studies reported percent removal and/or lacked consistent protocols for solid to liquid ratios and defined aqueous concentrations, which limits direct application. However, they hold value as an initial screening methodology informed by local knowledge and insights that could enable adoption for agriculture and other non-potable water reuse applications. While underlying removal mechanisms were presumed to rely on sorptive processes, this should be confirmed in promising materials with subsequent experimentation to quantify active sites and capacities by generating sorption isotherms with a focus on environmental conditions and specific contaminated water properties (pH, temperature, ionic strength, etc.). These organics also hold promise for the pairing of sorption to indirect microbial respiratory processes such as biogenic sulfide complexation. Conversely, there is a need to quantify unwanted contaminant release that could include soluble organic matter and nutrients. In addition to local availability and treatment efficacy, social, technical, economic, and environmental applicability of those materials for large-scale application must be considered to further refine material selection.