Harjyoti Kalita

Iron Nanoparticles Coated with Amphiphilic Polysiloxane Graft Copolymers: Dispersibility and Contaminant Treatability

Amphiphilic polysiloxane graft copolymers (APGCs) were used as a delivery vehicle for nanoscale zerovalent iron (NZVI). The APGCs were designed to enable adsorption onto NZVI surfaces via carboxylic acid anchoring groups and polyethylene glycol (PEG) grafts were used to provide dispersibility in water. Degradation studies were conducted with trichloroethylene (TCE) as the model contaminant. TCE degradation rate with APGC-coated NZVI (CNZVI) was determined to be higher as compared to bare NZVI. The surface normalized degradation rate constants, k(SA) (Lm(2-) h(-1)), for TCE removal by CNZVI and bare NZVI ranged from 0.008 to 0.0760 to 007-0.016, respectively. Shelf life studies conducted over 12 months to access colloidal stability and 6 months to access TCE degradation indicated that colloidal stability and chemical reactivity of CNZVI remained more or less unchanged. The sedimentation characteristics of CNZVI under different ionic strength conditions (0-10 mM) did not change significantly. The steric nature of particle stabilization is expected to improve aquifer injection efficiency of the coated NZVI for groundwater remediation.

Evaluation of soy-based surface active copolymers as surfactant ingredients in model shampoo formulations

A new non‐toxic soybean oil‐based polymeric surfactant (SBPS) for personal‐care products was developed and extensively characterized, including an evaluation of the polymeric surfactant performance in model shampoo formulations.

Phosphate Removal by Metal Cross-linked Biopolymers

Novel metal cross-linked alginate beads (MCA) were successfully used for aqueous phosphate removal. Batch experiments were conducted using three different concentrations of phosphate (5, 50, and 100 mg PO 4 3- -P/L) with 0.11812 gm (dry weight) iron cross-linked beads. About 94% phosphate was removed in 6 h from the aqueous solution having an initial phosphate concentration of 5 mg PO 4 3- -P/L. With 50 mg PO 4 3- -P/L, the beads were found to remove only ~41% in 6 but achieved 89% phosphate removal in 96 h. The second order reaction model fitted better for all the concentrations, and observed reaction rates were found to be 0.2979, 0.083, and 0.0181 per h for 5, 50, and 100 mg PO 4 3- -P/L, respectively. Interference of Cl - , HCO 3- , SO 4 2- , NO 3- , and natural organic matter (NOM) was investigated, and no change in the removal efficiency of phosphate was observed. To investigate the feasibility of using the MCA beads in real-life situation (e.g., eutrophic lakes), pouch experiments were conducted in two conditions, namely shaking and static where MCA beads were introduced into the water in pouches. The efficacy of beads in pouches was found to be the same as free beads (used in earlier batch experiments). The successful sorption of phosphate by MCA beads is expected to have enormous implications for nutrient removal and recovery.

Nanoparticle Delivery Vehicles for Groundwater Remediation : Sustainability Evaluation through Biodegradation Studies

The use of biodegradable polymer coated iron nanoparticles for groundwater remediation is an emerging area of research. A polymer coating increases colloidal stability of the nanoparticles. The lack of biodegradation of the conventional polymers used to coat nanoparticles is a major concern, and limits the application of nanotechnology for groundwater remediation. The authors have synthesized a soybean oil based biodegradable amphiphilic copolymer that improves the colloidal stability of the nanoparticles in aqueous environment. A mixed culture of bacteria is used in biodegradation studies, and biochemical oxygen demand, total organic carbon, and reduction in molecular weight of the copolymer have been monitored over time. Microbial growth studies indicate that the microorganisms responsible for the degradation can survive on the copolymer as the only carbon source.

Novel Arsenic Ion-Imprinted Polymer: Simultaneous Removal As(III) and As(V) from Water

In view of the extreme toxicity of arsenic on human and other living organism the U.S. Environmental Protection Agency (U.S. EPA) has fixed the maximum contaminant level (MCL) for arsenic as 10 ppb in drinking water. We now propose a novel method for the treatment of arsenic that is based on emerging ion-imprinting technology. The new product is expected to have the ability to remove both As( III ) and As( V ) simultaneously from water. Our ongoing experiments indicate that it can remove As( V ) very efficiently. Experiments with As( III ) are proposed in the near future. Results demonstrate that the ion imprinted polymer (IIP) has the capability to remove arsenic from water to below the U.S. MCL. ICP-OES and FT-IR have been used to analyze arsenic and monitor the IIP synthesis process, respectively. The new IIP is expected to be a very simple, reliable, and cost-effective to remove aqueous arsenic.