The concentration of hexavalent chromium (Cr(VI)), a toxic environmental pollutant and carcinogen, was determined in samples collected from Nacogdoches Wastewater Treatment Plant (NWWTP) using ion chromatography and UV-visible spectrophotometry (IC, UV-Vis). On reaction with 1,5-diphenylcarbazide (DPC) Cr<sup>+6</sup> forms a 1,5-diphenylcarbazide-Cr(VI) complex, which is then analyzed at 530 nm and 540 nm, respectively. Via ion chromatography Cr(VI) concentrations were in the range of <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.3499298pt" id="M1" height="8.69875pt" version="1.1" viewBox="-0.0498162 -8.34882 88.4177 8.69875" width="88.4177pt"><g transform="matrix(.013,0,0,-0.013,0,0)"><path id="g113-49" d="M241 635C89 635 35 457 35 312C35 153 89 -12 240 -12C390 -12 443 166 443 312C443 466 390 635 241 635ZM238 602C329 602 354 454 354 312C354 172 330 22 240 22C152 22 124 173 124 313S148 602 238 602Z"/></g><g transform="matrix(.013,0,0,-0.013,6.24,0)"><path id="g113-47" d="M113 -12C146 -12 170 11 170 46C170 78 146 103 114 103S58 78 58 46C58 11 82 -12 113 -12Z"/></g><g transform="matrix(.013,0,0,-0.013,9.204,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,15.444,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,21.684,0)"><path id="g113-50" d="M384 0V27C293 34 287 42 287 114V635C232 613 172 594 109 583V559L157 557C201 555 205 550 205 499V114C205 42 199 34 109 27V0H384Z"/></g><g transform="matrix(.013,0,0,-0.013,27.924,0)"><path id="g113-58" d="M244 635C114 635 38 519 38 422C38 317 111 240 217 240C236 240 255 244 277 256L345 292C311 140 203 39 59 15L64 -15C89 -15 150 -5 204 17C339 72 440 202 440 386C440 521 368 635 244 635ZM228 602C326 602 352 479 352 390C352 370 351 347 348 324C327 308 293 296 258 296C174 296 124 369 124 458C124 517 152 602 228 602Z"/></g><g transform="matrix(.013,0,0,-0.013,34.165,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,43.311,0)"><path id="g117-37" d="M535 290V340H323V533H265V340H52V290H265V84H323V290H535ZM535 -22V28H52V-22H535Z"/></g><g transform="matrix(.013,0,0,-0.013,53.847,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,60.087,0)"><use xlink:href="#g113-47"/></g><g transform="matrix(.013,0,0,-0.013,63.051,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,69.291,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,75.531,0)"><path id="g113-51" d="M412 140C382 77 369 73 315 73H129L270 222C362 320 402 379 402 466C402 571 322 635 234 635C177 635 130 609 99 576L42 495L64 475C90 514 133 568 201 568C274 568 318 519 318 435C318 349 255 267 193 193C144 135 87 78 32 23V0H405C417 45 427 89 440 131L412 140Z"/></g><g transform="matrix(.013,0,0,-0.013,81.771,0)"><use xlink:href="#g113-49"/></g></svg> and <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.3499298pt" id="M2" height="8.69875pt" version="1.1" viewBox="-0.0498162 -8.34882 82.1544 8.69875" width="82.1544pt"><g transform="matrix(.013,0,0,-0.013,0,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,6.24,0)"><use xlink:href="#g113-47"/></g><g transform="matrix(.013,0,0,-0.013,9.204,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,15.444,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,21.684,0)"><use xlink:href="#g113-50"/></g><g transform="matrix(.013,0,0,-0.013,27.924,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,37.07,0)"><use xlink:href="#g117-37"/></g><g transform="matrix(.013,0,0,-0.013,47.606,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,53.846,0)"><use xlink:href="#g113-47"/></g><g transform="matrix(.013,0,0,-0.013,56.81,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,63.05,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,69.29,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,75.53,0)"><path id="g113-55" d="M137 343C167 482 260 545 321 574C357 591 397 603 429 609L423 641C382 634 335 622 295 608C189 570 37 457 37 238C37 84 125 -12 242 -12C362 -12 447 89 447 209C447 311 374 393 267 393C247 393 226 386 204 376L137 343ZM227 337C318 337 361 256 361 173C361 105 336 22 258 22C176 22 126 120 126 240C126 266 127 291 132 310C155 323 189 337 227 337Z"/></g></svg> ppm at the influent and effluent, respectively. With the use of standard addition wastewater samples were spiked with a 0.5 ppm Cr(VI) standard of various amounts and subsequently analyzed with UV-Vis spectrophotometry. The spiked concentrations gave Cr(VI) concentrations in the range of <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.3499298pt" id="M3" height="8.69875pt" version="1.1" viewBox="-0.0498162 -8.34882 82.1544 8.69875" width="82.1544pt"><g transform="matrix(.013,0,0,-0.013,0,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,6.24,0)"><use xlink:href="#g113-47"/></g><g transform="matrix(.013,0,0,-0.013,9.204,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,15.444,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,21.684,0)"><use xlink:href="#g113-58"/></g><g transform="matrix(.013,0,0,-0.013,27.925,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,37.071,0)"><use xlink:href="#g117-37"/></g><g transform="matrix(.013,0,0,-0.013,47.607,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,53.847,0)"><use xlink:href="#g113-47"/></g><g transform="matrix(.013,0,0,-0.013,56.811,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,63.051,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,69.291,0)"><use xlink:href="#g113-55"/></g><g transform="matrix(.013,0,0,-0.013,75.532,0)"><use xlink:href="#g113-49"/></g></svg> ppm and <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.3499298pt" id="M4" height="8.69875pt" version="1.1" viewBox="-0.0498162 -8.34882 82.1544 8.69875" width="82.1544pt"><g transform="matrix(.013,0,0,-0.013,0,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,6.24,0)"><use xlink:href="#g113-47"/></g><g transform="matrix(.013,0,0,-0.013,9.204,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,15.444,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,21.684,0)"><path id="g113-53" d="M456 178V225H360V632H320C217 496 115 347 20 206V178H280V106C280 40 276 34 189 27V0H445V27C364 34 360 39 360 106V178H456ZM280 225H82C149 335 214 431 278 520H280V225Z"/></g><g transform="matrix(.013,0,0,-0.013,27.924,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,37.07,0)"><use xlink:href="#g117-37"/></g><g transform="matrix(.013,0,0,-0.013,47.606,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,53.846,0)"><use xlink:href="#g113-47"/></g><g transform="matrix(.013,0,0,-0.013,56.81,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,63.05,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.013,0,0,-0.013,69.29,0)"><use xlink:href="#g113-55"/></g><g transform="matrix(.013,0,0,-0.013,75.53,0)"><use xlink:href="#g113-50"/></g></svg> ppm at the influent and influent wastewater, respectively. The determined Cr(VI) concentrations through the ion chromatography and UV-Vis spectrophotometry are below the maximum USEPA contaminant concentration of 0.1 ppm. From the analysis, the NWWTP efficiently removes Cr(VI) before discharge into the environment through La Nana Creek. The removal efficiency for Cr(VI) was determined to be ≥92.8% along the wastewater treatment stages from the influent (aeration stage) to the effluent stages prior to discharge into the La Nana Creek.

Kefa K. Onchoke

Salomey A. Sasu

Determination of Hexavalent Chromium (Cr(VI)) Concentrations via Ion Chromatography and UV-Vis Spectrophotometry in Samples Collected from Nacogdoches Wastewater Treatment Plant, East Texas (USA)

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Advances in Environmental Chemistry

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Table of Contents: 2016

Determination of Hexavalent Chromium (Cr(VI)) Concentrations via Ion Chromatography and UV-Vis Spectrophotometry in Samples Collected from Nacogdoches Wastewater Treatment Plant, East Texas (USA)