Shamsuddeen A. Haladu

Polyaspartate extraction of cadmium ions from contaminated soil: Evaluation and optimization using central composite design

The occurrences of heavy metal contaminated sites and soils and the need for devising environmentally friendly solutions have become global issues of serious concern. In this study, polyaspartate (a highly biodegradable agent) was synthesized using L-Aspartic acid via a new modified thermal procedure and employed for extraction of cadmium ions (Cd) from contaminated soil. Response surface methodology approach using 35 full faced centered central composite design was employed for modeling, evaluating and optimizing the influence of polyaspartate concentration (36-145mM), polyaspartate/soil ratio (5-25), initial heavy metal concentration (100-500mg/kg), initial pH (3-6) and extraction time (6-24h) on Cd ions extracted into the polyaspartate solution and its residual concentration in the treated soil. The Cd extraction efficacy obtained reached up to 98.8%. Increase in Cd extraction efficiency was associated with increase in the polyaspartate and Cd concentration coupled with lower polyaspertate/soil ratio and initial pH. Under the optimal conditions characterized with minimal utilization of the polyaspartate and high Cd ions removal, the extractible Cd in the polyaspartate solution reached up to 84.4mg/L which yielded 85% Cd extraction efficacy. This study demonstrates the suitability of using polyaspartate as an effective environmentally friendly chelating agent for Cd extraction from contaminated soils.

Diallylbis(3-ethoxycarbonylpropyl)ammonium chloride: A symmetrically substituted monomer for the synthesis of an alternate zwitterionic-anionic cyclopolymer

Diallylbis[(3-ethoxycarbonylpropyl)ammonium chloride] (CH2=CHCH2)2N+[(CH2)3CO2Et]2, a new symmetrical diallyl quaternary ammonium salt, has been cyclopolymerized to its cationic polyelectrolyte (CPE) (+) I having pyrrolidine rings embedded in the polymer backbone. Polymer I would exemplify for the first time a cyclopolymer with each repeating unit bearing two identical 3-carboxypropyl pendants. (CPE) (+) I upon hydrolysis afforded pH-responsive polycationic acid (+) II, which upon successive deprotonation was transformed into a polyzwitterion acid (±) III and polyzwitterion-anion (± -) IV. Because of similar degrees of polymerization for I-IV, a meaningful comparison of their solution properties was possible. While I, II, and IV demonstrated polyelectrolyte like viscosity behavior, (±) III showed anti-polyelectrolyte properties. The anionic portion in (± -) IV controlled its solution properties. Polymer (± -) IV demonstrated remarkable antiscalant behavior; at a concentration of 15 ppm, it inhibited the precipitation of CaSO4 from its supersaturated solution with a scale inhibition efficiency of ≈100% even after 300 min. This study opens up the possibility of using the current polymer as an antiscalant in reverse osmosis plants.